The Hydration of Crotonic Acid and β, β-Dimethylacrylic Acid Citation Pressman, David (1940) The Hydration of Crotonic Acid and β, β-Dimethylacrylic Acid. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/p9jn-a073. https://resolver.caltech.edu/CaltechTHESIS:01132025-235049188 Abstract No abstract. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: (Chemistry) Degree Grantor: California Institute of Technology Division: Chemistry and Chemical Engineering Major Option: Chemistry Thesis Availability: Public (worldwide access) Research Advisor(s): Lucas, Howard J. Thesis Committee: Unknown, Unknown Defense Date: 1 January 1940 Record Number: CaltechTHESIS:01132025-235049188 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:01132025-235049188 DOI: 10.7907/p9jn-a073 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 16952 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 22 Jan 2025 19:05 Last Modified: 22 Jan 2025 19:06 Thesis Files PDF - Updated Version See Usage Policy. 32MB Repository Staff Only: item control page

'fHE HYDRATION OF ORotONIO ACID AND j,l,£•DIME'.fflYLACR'tLIC ACID TFlESIS by David Pressman In Partial Fultillm.ant of the Requirement for the Degree of Doctor ot Philoe~phy Oalifornia Institute of Technology Pasadena, California TABLE OF COVTE ~T TS Introduction l Hydration of Crotonic Acid 3 Hydration of f-,.~ft,•Di:methylacrylic Acid 10 Addi tiona.l D5.scus s ion 46 Su.r.1111a.ry 50 Propositions §1 Acknowledgment 1 !!!;troduetion The correlation of $·1:.ru ature with. speoifie reaction rate constants is seldom of value ·s:Lnee -hhe relative order ot the r a.te constants tor ~ aeries of similar compounds undergoing the same read.ion may cha.nge with temperature. I·b has been found empirically that when the loaarit..}:un.s of the ~J?.c:.:i ei.fie :regetion r ~1.te eonstants tor a single :reaction are plotted against t.he reciprocal of the abso 'ute temperature, a straight line gene;rally ia obtaizwd over a relatively Wide range of temperature~. Thus a speoific reaction rate eonste.nt., k, me.y be expressed in a form of the .fl.rrhenius equation, (1) where f is a Qonstant of unity with the dim.enaions of k, n is . the gas co ,:stant., T is the absolute temperature~ ;-i ia the heat of activE1:tion with the dimensions of energy and s is an entropy qlianti ty of activation with the dimensions of entropy. Although it is quite probable that a and Q, are temperature dependent, they usually may be assigned value$ independe11t of the temperature within e:x:perimente.l el"ro:r. The effect of struct'1.lre on a and Q then ean be discussed much more olearly than the ettect of structure on k, since the :relative orders of s or Q for e.. series of: similar cOl'llpounda undergoing the same reaction will not change with tempera:t;ure. 'I'he values of a and Qare enhanced by the fa()ta that, when the entNJP>Y quantities a.re takan as independent of the tEJmperature 1 the 2a heats 0£ activation ot the to~4 and reverse reac vi ona. $.re conneoted withe t h.ermo(\ynamiO· heat of the reaction by the relation,. and the entropy qW\ntities of e.etiv,atien ue c0nneoted i,Jj.th the thermodynamic entropy change in the re~otion by the telation,. 'liwse equat ions are derived e.t the end of the :tntroduotion. The hydration ot l ei'inio compound&, in a queous solution is es:baly.zed by hydronium ion and often is reversible according to the equation, tt ~ c=GRsR4 + lleO ~ + ) R R,.aCOHCHR 8 R.:t. 1 1 I.n ma.x:iw ensee both the forwa.rd and. reverse reactions proceed at ?il8e.sureable rates and the system eomea to a measureable equilibrium. This Iha one o~ the few: equilibrium ayatems in OJ'ge.nie C..fl.emiatry which lends itself :ree.dily to a t horough inveGtigation. n ,•; euld be interesting to correlate., theretere ~ the effect of V!'l.l"ieus substit tt0.nt s on the hea.ta and entropy quantities of e.ctivation for the hydration and dehydration reaetioons ·Ellld on the heat and entropy change in the hydrm.on reaction,. was under taken. A atudy ot the hydration ot eubstituted oorylio ij.Oicis These compounds have the added feat'lll'e that the double bond ot th~ eartGnyl group conjugate& with the otef:tnie dotible bond . This thepi_s presents th.e results. of an investigation of the hydration ot erotomo aetd to (.l.-.hydroxybutyJ:"ic acid and t he hydrat ion o't ~~dimethyl• a.erylie acid to ~ h;ydroxyis.ovalerio aeid. { 2b Derive.ti.on of equation 2. When the dUtere~ or the 1-oga.rt thmS ot the J>..rrheniue oque.t1on$ £or tbe fo~ra •a nd reverse rea.etio~ 1• tak<tn, there resul,ta the tquatf.()~, Difterentb.tion of th1• equation •w ith respect to l/'l giw8 1/r~- z: .. ~- ~ (5) Slll.C$ K ;;:.: kf/'&r-, e. oompariaon ot equation 6 with the van•t Hot!' equation., (6) DGrivatio:n of equation 3. When the t.T-termod~rnruna.o equationt, .~F=lnK= .. "1 l i + ~ l=tT Ri' R ( 7) are in.®rporated with equation 2 and eo:m.pared w:1tht~ equation 4., (3) 3 [Reprinted from the Journal of the American Chemical Society, 61, 2271 (1939).] [CONTRIBUTION FROM THE GATES AND CRELLIN LABORATORIES OF CHEMISTRY, CALIFORNIA INSTITUTE OF TECHNOLOGY, No. 709] The Hydration of Unsaturated Compounds. VII. The ~ate ?f Hydration .~f ~rotonic Acid· the Rate of Dehydration of /3-Hydroxybutync Acid; the Equ1hbnum belween Crotonic Acid and /3-Hydroxybutyric Acid in "Dilute Aqueous Solution ' BY D. PRESSMAN AND H. J. LUCAS Introduction Crotonic acid has been shown to hydrate slowly in the presence of boiling 20% sulfuric acid to form /3-hydroxybutyric acid. 1 This reaction is unlike the hydration of acrylic acid, since the latter occurs in the presence of hydroxide ion 2 while crotonic acid is not affected under these conditions. Moreover, only about 80% of the crotonic acid hydrates, for it appears that at this point it is in equilibrium with the hydroxy acid. The fact that the hydroxyl group enters into the /3-position during the hydration is shown by the identical properties of the acid obtained by this method and of /3-hydroxybutyric acid obtained by other methods. Also the ethyl ester of the hydroxybutyric acid prepared by this method is identical with that from hydroxybutyric acid obtained by other syntheses. 3 It was desirable to extend the study of the hydration on unsaturated compounds to an investigation of the kinetics of the hydration of crotonic acid, of the kinetics of dehydration of /3-hydroxybutyric acid, and of the equilibrium between crotonic acid, /3-hydroxybutyric acid, and water. Since it was known that crotonic acid is not hydrated at an appreciable rate at 25° in 1 normal nitric acid, 4 the reaction was carried out in 1.06 and '!.'06 normal perchloric acid solutions at 90.03 and 111.31 ° in order to obtain a measurable rate. These solutions were of 2.06 molal ionic strength. Nitric acid could not be used since its oxidizing power at the elevated temperature was appreci(ll Kaufel and Basel, Mollatsh., 53, 122 (1929). (2) Linnemann, Ber., 8, 1095 (1875); Erlenmeyer, Ann. , 191, 281 (1878). (3) Dewael, Bull. soc. chim. Belg., 34, 341 (1925). (4) Winstein and Lucas, THIS JOURNAL, 59, 1461 (1937). able, as evidenced by the liberation of the oxides of nitrogen. Data and Discussion Kinetics of the Reaction.-The hydration was found to be first order with respect to crotonic acid since the plots against time of the fraction of crotonic acid unreacted, C,/ Co, are practically identical for two runs at hydrogen ion concentration of 1.06 molal where the initial crotonic acid concentration has the values 0.0128 molal and 0.0249 molal. Here Co and C, are the molar concentrations of crotonic acid at the respective times, zero and t (Fig. 1). That the reaction is first order with respect to hydrogen ion concentration is evidenced through a comparison of the initial slopes of the plots of Ct! Co against t when the hydrogen ion concentrations are 1.06 and 2.06 molal. The slope at the higher concentration corresponds to a rate constant of 0.014, which is twice that of the lower, approximately 0.007. , However, hydrogen ion is not used up in the reaction and thus is constant during any one run. The independence of the equilibrium value with respect to the hydrogen ion concentration, except for small second order differences, is clearly evident from Fig. 2, which shows the complete runs of which Fig. 1 contains only the first portions. The equilibrium value of the crotonic acid fraction remaining is practically identical for both acid concentrations. The reaction then may be considered to be k1 H,Q + + H 20 + CH,CH=CHCOOH ~ k2 CH3 CHOHCH 2 COOH + H,o+ where k1 is the specific reaction rate constant of r both reactions to be monomolecular with respect to the organic reactant. -d(crotonic acid)/dt = k1(crotonic acid) (1) -d(hydroxybutyric acid)/dt = k2 (hydroxybutyric acid) 0.9 (2) d --....0.8 • 0 \ 1:.3 Rather than calculate k1 from the initial slope of the reaction rate curve, it was calculated by the analytical method which involves the integrated expression for a unimolecular reaction approaching equir rium (equation 3) and the equilibrium constan equation 4). l 0.7 O.G .___ _ __..__ _ ___._ _ ____, 0 20 (3) K=~=-•k2 1 - E (4) Here f is the fraction of tl:\e crotonic acid hydrated at equilibrium, x is the fraction hydrated at the ' time t, and K is the equilibrium constant. When the correct value off is chosen, a straight line results in a plot of log10 f/(f - x) against time. An example of this calculation is given in Table I, the data of which are plotted in Fig. 3. In order 30 Time, hours. Fig. !.-Hydration of crotonic acid showing the effect of hydrogen ion concentration and initial crotonic acid concentration on the initial slope of a plot of C,/Co against time: T, 90.03°; µ, 2.06 molal. • 0 Crotonic acid, Co molal (H+), molal + _•__ (k1 k2)t OglO E - X 2.303 1.0 0.02487 0.01282 0.01248 1.060 1.060 2.056 the forward reaction and k 2 is the specific reaction rate constant for the reverse reaction considering 0.8 I{ I ., 0.6 ~ 0 b0 ~ 04 0.2 80 160 240 Time, hours. Fig. 3.-Effect of variation of • on log1 0 e/(e - x) in the hydration of crotonic acid: initial crotonic acid, Co, 0.01282 molal; T, 90.03°; (H+), 1.060 molal; µ, 2.06 molal: ?, • = 0.775; 0, • = 0.834; ·0·, E = 0.892 0 400 600 Time, hours. Fig. 2.-Hydration of crotonic acid showing the effect of hydrogen ion concentration and initial crotonic acid concentration on the equilibrium between crotonic acid and /3-hydroxybutyric acid. Plot of C,/Co against time. The last point is common to the three runs. T, 90.03 ° ; µ, 2.06 molal. 0 200 0 e EB Crotonic acid, Co, molal 0.02487 0.01282 0.01248 (H+), mo'.al 1.060 1.060 2.056 to show the effect of a variation off, the value was changed from the experimental value of 0.834 to 0.892 and 0.775. It can be seen that the experimental value produces a straight line but the variations induce marked curvature in the plots of log1 0 f/(f - x) against t. It will be noted that the values very close to equilibrium were discardt~ since very slight titration errors at these points in 5 TABLE I EFFECT OF VARIATION OF • ON Loc,o ,/(, - x) IN THE HYDRATION OF CROTONIC Acm AT 90.03 ° I ,HCIO, = 1.060 molal; µ, = 2.06 molal; initial crotonic acid .:,,. O.oi282 molal. •= 0.892 • = 0.775 • = 0.834 log-'log E .:_ x log E ~ x E X J". • rium constant gave an excellent straight line. The slope of this line is (k 1 + k2) /2.303. The data of the several runs made are plotted in Figs. 4 and 5 as log10 E/(E - x) against time. 2.0~-- -- - - - - - - - - - - - - - , l. 1.1 1.6 4.0 6.1 11.4 27.1 31.5 39.8 47.6 56.9 69.8 99.6 127 . 1 148.8 179.8 221 340 389 468 677 1.000 0. 995 .985 .970 .955 . 917 .815 .795 .756 .714 .665 .616 .520 .482 .385 .331 .282 .212 .204 .177 .165 1.6 0.003 .008 .0155 .024 .0445 .1085 .124 . 149 . 182 .222 .267 .372 .496 .579 .703 .854 0.003 .008 .0145 .022 .042 .101 .115 .138 .168 .204 .244 .335 .439 .506 .601 .708 0.003 .0085 .017 .026 .048 .118 .136 .163 .199 .245 .296 .419 . 572 .681 . 860 1 .079 0.4 20 40 30 Time, hours . Fig. 5.-Hydration of crotonic acid at 111.31 °. of log10 ,/(• - x) against time . 10 (H+), molal Co, molal • 1.6 H EB I "' :::::: :o.8 b7i 0 ...;i 0.4 0 0 80 160 240 Time, hours. Fig. 4.-Hydration of crotonic acid at 90.03°. Plot of logJO , /(, - x) against time. • 2 ."6 1.060 0.01282 -~ 0 Ell 2.06 1.060 0.0186 .774 2 .06 2.056 0.0200 .760 50 Plot As a test of the stability of the system at equilibrium one run was permitted to stand for three hundred and fourteen hours, whereas the system apparently had come to equilibrium after seventythree hours. However, there was no observable shift in the equilibrium value of the system. These data are shown in Table II and plotted in Fig. 6. TABLE II STABILITY OF EQUILIBRIUM IN THE HYDRATION OF CROTONIC Acrn T = 111.3°; µ, = 2.06 molal; HClO, = 2.06 molal; initial crotonic acid, Co = 0.0200 molal. Time, hrs. 0 0 .4 0 . 98 1.63 2. 62 4 .25 C,/C0 1 .983 ,948 0 .910 0.855 0.774 Time,hrs. 7 . 33 12.75 23.57 48 .57 73.1 C,/Co 0.649 0.499 0.342 0.250 0 .236 Time, hrs. 96.6 120,9 145.6 169.6 314 . 6 C,/ Co 0.238 0 .238 0.238 0.238 0.240 ,.-,.1.2 (H+), molal C~. molal I 1.2 µ,, molal the determination of the crotonic acid concentration would cause very appreciable errors in the value of log10 E/ (E - x). • In every case, the experimentally determined value for Efrom the equilib- µ,, molal ~ 0 Ell 2 . 06 1.060 0 .02487 .836 2.06 2.056 0.01248 .829 The calculation of the specific reaction rate constants for the dehydration of /1-hydroxybutyric acid was carried out in a similar manner. In this case Eis the fraction of /1-hydroxybutyric acid decomposed at equilibrium and x is the fraction decomposed at the time, t. A plot of log10 E/ (E - x) against time for iS~bydroxybutyric acid is found in Fig. 7. The specific reaction rate constants and 6 1.0 The equilibrium constants, 5 at 90° and 3.4 at 111 °, correspond to 84 and 78%· hydration, respectively. These data substantiate the value of 80% hydration observed by Kaufel and Basel, 1 in boiling 20% sulfuric acid . 0.8 . 0.6 d (5 ----- 0.4 0.3 0.2 I 0.2 "' :::::: 0~-~-~-----~-~-~-~ "" 320 240 160 Time, hours. Fig. 6.-Stability of equilibrium between (3hydroxybutyric acid and crotonic acid when approached from crotonic acid. Plot of Ct/ Co against time. Initial crotonic acid, Co, 0.0200 molal; T, 111.31 °; (H+), 2.06 molal; µ., 2.06 molal. 0 80 ~ 0 ~ 0.1 o~---+--+----1>----+---' 10 4 6 8 Time, hours. Fig. 7.-Dehydration of (3-hydroxybutyric acid. Plot of log,o e/(e - x) against time. Initial (3-hydroxybutyric acid, C0, 0.0225; e, 0.228; T, 111.31 °; (H+), 2.01 molal; µ., 2.01 molal. 0 the equilibrium constant determined in the dehydration run on /3-hydroxybutyric acid are in excellent agreement with those obtained in the hydration of crotonic acid. This proves that a true equilibrium occurs since it can be approached from both sides. The kinetic data obtained are listed in Table III. Experiments 1 to 5 deal with the hydration of crotonic acid while experiment 6 is concerned with the dehydration of /3-hydroxybutyric acid. The specific reaction rate constants, k1 and k2, for the forward and reverse reactions are listed along with the constants which have been corrected for hydrogen ion concentration. The latter are listed as k1/(H+) and k2(H+). The constancy of these corrected values with acid concentration checks the observation that the reaction is first order with respect to hydrogen ion concentration. 2 Effect of Salt.-It is interesting to note that the equilibrium is shifted to the right when hydrogen ions are replaced by sodium ions. This shows that there is a relative increase in the activity coefficient of crotonic acid over the activity coefficient of /3-hydroxybutyric acid when sodium ions replace hydrogen ions. This effect was also observed in the case of crotonaldehyde. 4 In Table IV a comparison is made of these effects in the two cases, crotonaldehyde and crotonic acid. It is evident that the equilibrium constant, at constant ionic strength, increases with decreasing hydrogen ion concentration. TABLE III KINETIC DATA CONCERNING THE HYDRATION OF CROTONIC Aero (1 TO 5) AND DEHYDRATION OP (3-HYDROXYBUTYRIC Aero (6) Temp., •c. (H+) (µ), M Initial crotonic acid , M k, X 10 2 ks X 10 1 1 2 3 90.03 90.03 90.03 1.06 1.06 2.06 2.06 2.06 2.06 0.01282 .02487 .01248 0.752 .745 1.43 0.1485 .1445 .299 Average 4 5 111.31 111.31 1.06 2.06 2.06 2.06 .01860 . 0200 3 .485 6.765 1.025 2.135 Average 6 111.31 . 02249a 2.01 2.01 of initial fl-hydroxybutyric acid. 6.48 1. 915 a Concentration k1/(H•) X 10 2 k1/(H•) X 10• K 0.710 .703 .696 .703 3.29 3.28 3.29 3.23 0.140 .1365 .145 .140 5.05 5.14 4.80 5.00 .97 1.03 1.00 0.955 3.41 3.16 3.28 3.38 7 TABLE IV EFFECT oF Aero CONCENTRATION AT CONSTANT IONIC STRENGTH ON THE EQUILIBRIUM CONSTANTS FOR THE HYDRATION OF CROTONALDEHYDE AND Crotooaldehyde µ 1.90 1.93 1.96 1.98 * (H+) K µ 1.905 1.432 0.956 .478 0.795 .816 .873 .930 2.06 2.06 T = "25° Acm CROTONIC Crotonic Acid (H +) T = 90• K 2.06 4.80 1.06 5.10 T = 111.3° 2.06 3.16 2.06 2.06 3.41 1.06 Thermochemistry of the Reaction.-Table V contains the thermal data for the reactions involved. The heat of the reaction, t:.H, the heats of activation, Q1 and Q2 of the forward and reverse reactions, and the temperature coefficients are listed individually for the runs in the solvents of different acid concentration. The values of k1, k 2 and K for the two runs at 90.03° in 1.06 N perchloric acid were averaged in this calculation. This averaging accounts for the discrepancy between the difference in the heats of activation and the heat of the reaction, since the latter was calculated from the temperature coefficient of the averaged equilibrium constants and the former from the averaged values of the rate constants. The heat of activation of the forward reaction is smaller than that of the reverse reaction. Thus, there results a 6H of -10.1 kcal. for the reaction. However, the heat of activation of 38.0 kcal. for the forward reaction is larger than any of those observed previously for unsaturated compounds, which were 23.4 kcal. for isobutene 5 ; 21.04 kcal. for methylethylethylene 6 ; 18.92 kcal. for trimethylethylene7; and 18.3 kcal. for crotonaldeTABLE V * THERMAL DATA CONCERNING THE HYDRATION OF CROTONIC Acm ~- ~t tfffr 1Naw (~~ 9~ H.Y"li, !'11!!1:,<lo, ~~~~ --9-:-8- 4,..,.Q8 ii..94 - ~ +.i-4 ~5 Average 3,S...00.-- 48-:-:t ~4d:1'~ 1~2.,.Qi a't-,-86 4'7:85 hyde. 4 The heat of activation for the reverse reaction is 48.1 kcal. for crotonic acid as compared with 24.5 kcal. for crotonaldehyde. The fact that the hydration of crotonic acid • liberates 10 kcal. while the hydration of crotonaldehyde liberates only 6 kcal. indicates that (3hydroxybutyric acid is relatively more stable in (5) Eberz and Lucas, THIS JOURNAL, G6, 1230 (1934). (6) Lucas and Liu, ibid., G6, 2138 (1934). ' (7) Liu and Wei, J. Chinese Chem. Soc., 4, 297 (1936) . * Sec page 36 aqueous solution with respect to crotonic acid than aldol is with respect to crotonaldehyde. Resonance explains the relatively lower stability of the aldol. Crotonic acid in the acid solution can resonate between the unexcited forms Q. ,f"O: c-c=c-c/.· • C-C=C-C.., .. ~OH '-OH + while (3-hydroxybutyric acid resonates between the unexcited forms H :0: .. I ;fo: c-c-c-c( .. • OH H :0: .. - I o: c-c-c-c(·· ~ OH + On the other hand, crotonaldehyde can resonate between the unexcited forms 0: II C-C=C-CH :o: + I C-C-C=CH while the hydration product, aldol, can exist only in the single unexcited form H =r ~= C-C-C-CH Thus, when crotonic acid hydrates it goes from a structure of principally three resonating forms to one of two, while crotonaldehyde loses nearly all of its resonance energy upon hydration. Hence, it would be expected that the evolution of energy during hydration would be less in the case of crotonaldehyde than in the case of crotonic acid, since each must retain energy equivalent to its loss of resonance energy and since the loss for the former is greater than for the latter. The difference in the heats of reaction, viz., 4 kcal., is the difference in the resonance energy changes. Ester Formation.-Gehrke and Willrath 8 have shown that (3-hydroxybutyric acid loses water by itself to form a compound of lower free carboxyl content. This could be a linear ester, lactide or lactone since saponification of the compound of lower free carboxyl content liberates all these bound groups. In any case, it was stated that in a 0.1 molal solution of the bydroxy acid at 100° only 95.5% of the carboxyl groups are free. This would mean that 9% of the molecules are com(8) Gehrke !lll<l Willrath, Z. physik. Chem., A142, 301 (1929). 3 bined as linear ester molecules or 4.5% are in the lactide or lactone form. Linear ester formation would be essentially negligible because of the high dilutitm, if it iiJ assumed that in the pure acid, the extent of this .reaction would be about 50%, as generally is the case in the formation of simple ' esters. At the concentration of 0.1 molal, esterification of this 'type would be only abovt 0.05%. Likewise, lactide formation and esterification of the /3-hydroxy acid by crotonic acid would be negligible. However, lactone formation and lactone hydrolysis are essentially unimolecular reactions, and thus the equilibrium would not be affected by dilution. The formation of a fourmembered ring as·in the lactone would result in a ,low value of ~ lactone formation which may well be of the order of 5%. Thus the equilibrium values as listed in Table III may be as much as 4.5% in error, due to the uncertainty of the /3-hydroxybutyric acid concentration. However, in the important calculation, that of the heat of reaction, a ratio of equilibrium constants is taken and these errors occur then as second order corrections and are thus negligible. Experimental Materials. Crotonic Acid.-The crotonic acid used was the Eastman Kodak Co. product which had been recrystallized from water. It melted at 70.5-71.0 ° uncorr., and analysis for unsaturation showed 1.000 double bonds per mole. /3-Hydroxybutyric Acid.-This was prepared by the method of Kaufel and Basel 1 in which crotonic acid is hydrolyzed in the presence of boiling 20% sulfuric acid. The reaction mixture was neutralized to methyl orange with a freshly·prepared paste of calcium hydroxide in order to remove sulfuric acid. The solution was filtered from the solid calcium sulfate and concentrated by vacuum distillation. This also removed most of the unconverted crotonic acid. A solid separated and was filtered. This was most,likely a mixture of calcium sulfate and calcium /3-hydroxybutyrate. The resulting sirup was extracted several times with ether to remove remaining crotonic acid. This was eohtlnued until the sirup indicated negligible unsaturation when analyzed by bromination. Upon standing in a vacuum desiccator over sulfuric acid, a precipitate of calcium hydroiqrbutyrate separated from the sirup. This was washed with alcohol and dried in a vacuum desiccator. An ash determination showed 15.9 and 16.0% calcium; calculated for calcium hydroxybutyrate 16.2% calcium. Since difficulties would occur in obtaining a known samJjle of the hydroxybutyric acid itself due to its self esterification and water loss, the calcium salt was used in its place since it could easily be weighed out quantitatively. Perchloric Acid Solution of Constant Ionic Strength.Equal portions of 60% perchloric acid were weighed out. To one was added enough sodium hydroxide to neutralize one-half of the acid. These portions were made up to equal volumes with distilled water. They were of equal ionic strength but unequal acidity. . Method of Analys1s.-The solutions~e'. anafyzed by a quantitative bromination method. fhe solution to be analyzed was added to an excess of 0.05 normal bromatebromide solution in an iodometric flask. H the solution to be analyzed did n_ot contain a strong aclc( 5 ml. of 6 N sulfuric acid was added at this time to liperate bromine. Potassium iodide.solution was then added and the liberated iodine titrated with 0.02 N sodium thiosulfate solution. In the analysis of crotonic acid, it was fotlnd that a 50% excess of bromine gave theoretical bromiili!-tion in fiye minutes while a 300% excess introduced an err of only 2% after one hour of standing. Experiments concerning the ' effect of bromine on hydroxybutyric acid showed that -it substituted at the rate of 0.04%/minute when the mole ' ratio of bromine to /3-hydroxybutyric acid was unity. , Thus, the error incurred by the bromination of hydroxybutyric acid would be negligible under the conditions of analysis using a five-minute bromination period and a 50 or 100% excess of bromine. Procedure of the Reaction.-Standard solutions of crotonic acid in perchloric acid were made up by roughly weighing the crotonic acid into an approximate volume of standard perchloric acid and then analyzing 20-ml. aliquots by bromination. The solutions of ,B-hydroxybutyric acid were made up gravimetrically by weighing out accurately a portion of calcium hydroxybutyrate and then making it up accurately to volume with perchloric acid solution. The runs were made by sealing off 20-ml. aliquots in test-tubes. These were placed in a thermostat at either 90.03 ° or 111.31 ± 0.05 °. Tubes were withdrawn from time to time, quenched in water and the contents analyzed by bromination. Summary A study of the reversible hydration of crotonic acid to /3-hydroxybutyric acid in 1.06 and 2.06 normal perchloric acid solutions of ionic strength 2.06 at temperatures of 90.03° and 111.31 ± 0.05° was made. The hydration is first order with respect to crotonic acid and hydrogen ion. The dehydration is first order with respect to /3-hydroxybutyric acid and hydrogen ion. The equilibrium is shown to be approachable from either the crotonic acid or the /3-hydroxybutyric acid side. The equilibrium constant is 5.0 at 90° and 3.4 at 111 °. In solutions of constant ionic strength the equilibrium shifts toward crotonic acid with increasing acid concentration, thus showing that the replacement of sodium ion by hydrogen ion relatively increases the activity coefficient of /3-hydroxybutyric acid over that of crotonic acid. The energy of activation is 38.0 kcal. for the hydration and 48.1 kcal. for the dehydration. The heat of the reaction is thus 10.1 kcal. The 4 kcal. greater heat of reaction than that which accompanies the hydration of crotonaldehyde is ex- plained by a lower loss of resonance energy in the hydration of crotonic acid. PASADBNA, CALIF. RBCIUVBD MAY 29, 1939 [?ontribution from the Ga tes a nd Crellin Laboratories of Chemistry, Califo r n.ia Institute of Technology , No. 75J] 10 The Hydration of Unsaturated Compounc1.s . VI1!. The Rate of Hydr a tion of !!_ ,.§.-Dimethylacrylic l.i.cidi the P.ates of l'.lehyd.ration and. Decarbozy1a tion of i-Hydroxyisovaleric Aeid: t he Reat of 'Hy dration of DimethfLi crylie Acid in ~ilute Aqueous Solution '.By David :Pressman. and H. J. l,,u.0$.s ,. In order to det ermine the effect of various substitu.enta t1pon the heat of hydr a tion of the et,hyl.e nic double bond, a nu,mber of compounds must be stud.ied. It ie r easonable to belie-vie that the influen.c.e of t he sub$t i tuent may be exerted through two prineipa.l e:f'f ect 1.i . is the ind:uetive effect , is shown by a ll su.bstit1:ienti . One, wr. i cb. The other, whie.h affeetlil the double 'bond cha racter through resonance, is exhibited by only certa in su.'bstitu.ents . In ad,dition there is bcnmd. tc be a certa in inte.r- a otion between these two effbets. It is the pu.rpo .s e of the p resent hyd.ra.tion studie.s to evaluate the two 1>rinci:pal effects and. thei:r interact ions . The heats of hy-drat~n t~re determined from equililn•ia. or kine ti c d.ata a.s in previous work . 1 2 t ...,.,. _____ ___ _ .., __ . --(1) W. :b' . 1'iberz and It . J. Luca s ., !::!!!?. i~~~~ . .Ss, 1230 (1934). ~ (2) (3) ,.. •3 ~ ~- s. Wins·tei n and H.J . Luca s, lb.id . , ~ . 111-61 (1937). I) . Pressmen and R. J . Luca s , Ibi d . , .2!,; 2271 ( 1939 ) . A stud.t h being m,tr,de a.lso of the kinetic s 1: 1. nd mechanism of t he hydrat i on and dehydra tion rea etions and clata are being obtaine~ for a correla tion of stru.ctu.ra.l effects upon rea ction velocitiea a nd. heats of' a,ctiva,tion of the hydration a nd dehydration reactions.. At the aame ti me th.e inflµence of acid and ba.se ca.talysts and of the ionic st~ength upon these two rea ctions i's be ing observed . Since t he hf.;,&t of hydra tion of croto nic $.Cid hR-s b een det e r mined a lre&.cly , 1t wae d.aei:rti.bl e to ex tend the stucy of t he ryJ.ration of unsatura ted. compound.s to include t hat of J?.&-di methylac rylie a.oi{l and. its e qu.11ibriu..m with ,e.-hydroxyisova.leri e acid. No :reference ha s been found conc er ning either the hyd.ration of £...f.-d.i:met.hyli-:i.crylic a oid. or the dehydnt ion of ! - hydrox.;:riiova.leria a ci d. . The :pl an of work was to obta in the heat of hydration from t he k inetic consta.n.ts of the hydr a tion of t he unt¥1tura ted acid a nd of the dehyd.ration of t he hydroxy a.ci d. a nd also from t h e equilibria. between the t .ro acids a t two tempet-atu.r es in dilute perchlorie a ci d aolution r..s in previous work . !fow-ever. t l\e deea rboxyla tion of i-hydroxyiso'!fa larie a cid to tertiary butyl al cohol under the conditions of the experiments is e, eompl:l.ea tion wM.eh does not p ermit a direct mea surement of the equilibria . Decarboxy-ltt. tion in a~ue-ous solution hr..s not been reported .for either k,- hydroxybutyrio a cid. or !.,..hydro,:yisovderic acid.. Indeed, the great stability of the eq_u.i lib.:d.um between t he former and crotonic a ci d is d.€fin1te evid.enee t M.t it could. d.eoa.rbo~yln,te only a.t am. infinitesime,l r ,e...te in 2 I perchloric a cid a t a t$m:p e:ra tu.r~ of 100°. However, two homo logs of the .fi-h;yd.roxyi sova leric acid. , nar.1ely- g•methyl--1-hydro,:_yisovalerlc a cid4 {i!.nd !!•Qi... dime thyl..jl- hyd.:roY.yi sovaleric ~cid• 5 deoa.rbexyla. te - - - - - - - -- - - - - - - - - -- - - - - - -- - - - ( 4) ~ ~ • • Giljarow , J. Rus~ . :,Phys . Chem . 0-e $~1l ., ~ ' 501 (1896 ). ( 5) S. Reformat sky and B. Plef:lconoagof:f, ~ -. ~. 2839 (1895) . in hot aqueous solution to j-'i.eld di:nethylathylcar binol e.nd. dimeth.,vlisoP ropylca.rbinol i r e spectively. 12 In ep tte of the deearbox:,h.tion rea ction , t he hyo.rat ion il'.nd d.ehydl'a t1:on 1 constants t!!.long with the d.e ca. r bo:x:yl a tion consta n}.s -001110. be determined. from the k inetic da t a obta ined in the hy r-1.r a tion a nd dehydration ex,_pe:t1 • ments . Th.e hyd.ra.tion stU.flies we:re Ol!!.r:ried out a t hyctrogen ion concentr,'i.l, tfon.s of a :-:proximately 0 . 3, 0 . 5, and 1 . 0 ,Nat &i. n ionie strength of 1. 0 i a nd. a. t 1 ioJllic strengths of o.6. l. O, and 2. 06 _!! at a hydrogen ion oanoentmtion of stuclies were ea.rried out ~t ionic st rengths of 1 . 0 a nd 2. 0 ~. with a eoncantrationsi of a:pproxims tely 0 . 5 and 1. 0 ! at an ionic strength of l. 0 EDeca roo.,-.ylation consta nts· were &.lso deter-.nined ind.ependently at - ionie strengt h s o.o. 1. 0, a nd 2 .. 0 N, lrq..t in the absence of added :perchloric aei d . These values vere founcl to be quite di:ffei~ent from those det er.. mined in the pe rch.lorie a,cid solutions indicating th.at t here are t,-ro mechani sms of deear'boxylation . The hydration sturlias were ca rried out a t s2 . 45<. , 99. 85° , and 11L5-5° while the d.ehyclrati on a n,l daca.rboxyla tion s t udie s were carried out a t the. t wo higher temperature$ only. Perohlo:ri o aoitl. r a ther than nitric or a hydrolw.Hc acid was u.sed. since ni trio acid. h~,s a dee HJ.eel oxidizing ''"ction at th<3 elevated temperatures r~d hy11ro g:en rui,l i des might add to the ethylenic linkage. for the deltyd:ra tion of f-hycl:ro:x:yisova le:ric a c id. ar e shown in Pig s. l a nd 2, Fir, --~ Plot ill$ t· l ry,. otion 1/°-'>• (!/~). - - r (B'1 normal n.as• -W.85° i 0544 ~ 1.,000 . -<tI 1.000 o. 46o Oi544 0.480 lo 1. 2 .1 leO 1 .. 0 2"1 I I I· ~1,0 ( j!:/flo) ryli ot ot t ti n: o d• 1/£o,. ( - (Ri- ) 1 ..I!:- no 9. 6° 1.0 1.0 2 1 0 () • 111. 5• -0~ ..... o. o_. o. 1.0 1.0 2.1 0;01 0.;01 0.01 o. 01e40 0 01 0.01 l r espectively . .Here Q /c0 • the fra ction of t he original a eid either 1 satura ted or unsatura.t ed , t-,hieh i g present &. e the u.nsfl>t ura.te.(l. a c1il; i s plo-tterl agta.i nst ti me . Si nce both hyd.r&. ti on a nd dehy~:rs tio:n ct1rves a:p.p;ro$.Oh the axis asympto tically, it is evident U·1.B.t eventually a ll of t he (li metJiyl- rr ypica.l decsrboxyla tion curves for ft-hy<lroxyisovn,leric e.cid in tl).e @ .bsence of p erehlorio n.cid. a re sh.own in ]'ig. 3 whel'e ~ /9-o• the fracti on of t he original !-hydroxy acid present . h :plottetl a.gains~ time . Since the fn.ction r emain.int e,:p-prom.o.hes zero. a ll the c;ctd. decarl;io:x:yl a tes eve:nt,1,?,1:-ly. The slow chang.e in t..lle va.lue of 2.:/9.o for ! ,_i- o.brethyla.orylic r,i,cict (}?ig . 3) indic&', tes tha t t his deoa rboxyla tion reaction is negl i gible conr_pv>,red with. The st:rair_!>"~ r.n t line cha.:ra cte r of t h.a nl' lot of lo.l'l' C / ~1 0 • e 10 -Z{)• iud.'lcG.tes tha t the hycl ration of .fl ,,a... di me thyla erylic 2.nid. iaitiG,lly i s :fir$t o:rc1er with respe·o t t-0 t he unsa turated. a.ci(l ( F'ig . 4) . Moreovel', the equality in. thfll slope$ ef these curves for run s a t the !5ame hydrogen ion concentration a.erylic a cid indica tes the s ame thing. The reaction the:vefore is p eeuclo- hydrogen ion concentration ~;nd inere@.si.ng ionic $trengths sh.ows the de:pend.ence of t h e ra.te consta nt upon the 1:,e q_u.anti ties. h Th$.t the hydration first (i)fd.e:r vith respeet to the hydrogen ion eon.¢ e-l'l.t~tion @ n be S0en from a eomp at':i.$0-n o:f t he slopes of the cu·rve s for diff.e rent hyelrog-en ion V ½/Co' r, ,J ~.,•' .o., o.? I) G, I .n I oar ;:,c:yl tic ot /!.. yla :ryli c1d oid t 111. 5° 1n e. ence ot perohlon a.o4.4. tr ction ot org aoid ~lll;LJ.u.w,16 • s,.j9J,. 1,_., -dilnothyla ryli 1-- -o- /0. ydrom Plot ah\at a.old o.·o 0. 020 0. 0250 0. 0237 17 o,,,::. o., .. I O. o'i, I p t 0£ l ,, J. - 10.W~ r ation (B ) no 2.45 0 • fl} CJ ~ q) ~~ l 1;000 1.000 o, ♦,302 o. 10 o.48 thy 1.0 .o 0.00973 o.00414 0.009 o.a o.ooe1e 1; 1.0 0.0101 2.1 o.oos20 1.0 l. 0.0061 9.8S 0 -0--c:,~ 1.000 o.ao2 0.601 o.s o.oo 88 0.00875 • o.-. ~...-----------------, Jo 0 lot ac ins 10WP tor t l e - • 99. ~~ (J ~ o. o .o c.. l • 1 0. 0250 o. 287 20 deca.rbo.eyla t ion constnnt, ]s 3 , in the pl"e sanoe of a cid. i s the ·S'Wn of t h e a cid catalyzed a nd unoa t a lyzed. reactions, equs.tion 2 ka 0 = .!;C . H ( 2) + ~3- Using A to r epr esent t he concentra tion of ~ .Ji- d.imethyla.cryl i c a ci d, -:B of f -hydroxyisQva.lerie a cid , a.nd -C of t ertiv,cy butyl alcohol, t :he time . :ra te of change o! these eoncentra.tl ons is given by e ~ua tion s 3t ~nd. 5. ~ '- '·i:, k~ d!/d)i : d!_/ cl! = .!El.! ~/d,! x:: - ~1! - (3) (4 ) (Js2 + Isa)] E~ (5) 1~hese e q_u~tions. integr a te to give t he foll owing gene r a l aA-pr essi ons where t he subso:ri;p ts , .Q, a.-:ncl !, indiei1i,te t h ~ concent r a.tions. a t time initial a.nd time! respectively . :!1 t) (t - t ) ! e 2 't ,_ - ...;!.{) · + !I! e J::. -~ 8 =r (6) (g ) + [~2 ] 0 - ~(!£1 + g)J (10 ) -(k~ _ .. + __ k 2 + _3 k) + / <.t1 + E;s + };3 )~ - 41s1 !s 2 ,--- - -- - - -- -- / Qs_,. + 1f2 + lf3) ~ - 4_!1 ~a 2 (ll} (12 ) 21 Qs,. + .i )! ~ ... <151 + a).! fil (13) (Ji - !!) (15) In the case where A ~ f:1!~ ··v 5a =- 0 :md· ....C0 = 0 a t ,· t = - ( 2. £!! - .! Qi - i Jll ~ - v =0 ) (16) Since the hyclra tion and dehydrat ion reactions were followed by a nalysis for unea.turation, !! , the concentra tion of the ft ,A-.dimethylThe va lue of At,/J::o or !t/!r; coul d. .... be det ermined expe!'imenta.:!.ly since known amounts of .@.,f-dimethyle~crylic a crylic a cid alone was d.ete:rmb1ed . - a cid or .fl.-hydroxyisovaleric a.e1d were present initia lly . Hence equations 13 and 16, which deter.nined ~lueis 0£ !i/!o a.nd Ai/!o were those used in the ~va luation of the eonst~nte, ,!£s and ,!s3 • ! '!?l~i2.!! ,.e! ~ ~r~i~~ ~ • ~ ....... Since lEi happens to 'be larger than ks, and lsa is very close to ! 2 in niagnitudei the actual r ate of dehydra tion of .fl.-hydro:xyisovn.leric aoid is $.lwa,ys sma ll compared to the a ctual r ate of hydration of the !,!... d.imeth.ylaeeylie acid in those experiments where dimethylao:rylic acid is the starting material. Ther@fore ., it is possible to obta in t.he hydra tion <::on$tant, ~ 1 , fro m t he initfa.l slope of the p lot of log10 Ao/!! a.g@,inst ! for the hycl;r a tion of the unsatura ted compound. "'·ith an error of less than 1% d.ue to th.e rev~rse These plot .s a re straight lines a t lea.st up to o. 4 hydrated a s reaction . shown in ]/'ig . 4. It will be noticed. tha.t the interee:pt on the abscissa is posit ive. This is due to the time l ill.g i.n reaching the thermostat temperature . 'l'he specific hydration constants, ,!£1 ; for hydration experi- ments are tabulated in Table I. Table 1 Rate Constants for Hydration of Jl ,!--Dime thyla.<i:ryli¢ Acid + (R) F Norme.l Normal P:.o fi!ole.r 1£1 .. 1 hr k .=l.:fl Relative (B:90 ) yk -1 0.0265 0.0255 1.000 ...! - Qi 1+5ci l.000 l.O 1.000 1. 0 o.ootn4 0.544 0.302 1.0 l. o o.009g4 0.0265 0.0255 0.01525 0.01015 0.00873 0. 00920 o.ooa65 0.0137 0 .0235 ,) . 'J06e?S 0.165 0.165 0. 610 o.48o o.6 2.1 0.00973 o.ozso 0.963 1.059 0.0287 0.0224 o. s45 0 . 0)~90 1.082 1,85 g50 1.000 1. 000 0.544 o. 302 1.0 1.0 1.0 l.O 0 . 610 o.ltSo o.6 1.010 1.0 1.0 2.1 2.1 0.00516 0.00686 0. 00883 o.oos75 o.ooso6 0.0930 0.165 0.165 0.171 0.0530 0.176 0.151 0.13s 0.314 0.507 o.~o o. ·9 0.507 0.552 0.935 o.os44 1.000 1.000 1.0)8 0.131 1.068 o.s36 0. 214 1.901 55° o.a44 o. $0 o.oos6o 0.006~0 0.007 9 0.126 0.0970 0.145 .2~ls,ul£},t!.,oA .2i !M ;,Q~dpaj;,!OJl ~ l¾c4~r12.P~~U,.~%! £.~.@t~t~. ka ~~ 5a• a~t!Q.n [!J. g__~ ~.-..On the other h ancl, it is not p r a ctica l t-0 ca.loula te the dehydration consta,nt, ~ 2 , from the initial slope of the 0.789 o.l+g5 0. 705 2 d.ehyd.ration cnrve since the decarboxyla.tion ia t r...king pl a ce l;lt a. eomp~ r able r a te and the eql.1.ilibrium li es well on the hyd.~·a.t ea. side . Ths most t"isefttl. e qw;,tion for the det ermina tion of both the dehydration consta nt, !!~• ~nd the deca.:rboxylntion consta nt, .t 3 , is equation 16. (~o.j_ - ~ fil) is a. stra~gb.t line with the slop@ !af~ ... !) when the correct va.lua s of ~ a nd ! a.re used. Since A!/!o pe.eses th.rough a ma:dmrup., the •straight line plot rea ches a. maxi mum v.,.lue o:f A!/~ and of (,2 <:t.,t a nd then retu.rne upon itself. - §; ll) Different va lues of Qi and ! wore substituted. in the experimenta l data. until a straight line wa s obtained. Fig. 6 d.emonstr1-1tes the effect of vi::.ria.tions of r& and .e, on a plot of et) • .From t hl?. slope of this stra ight line !£:a ~!1~ £o a.ga i ns t• (!!· -~t - .! -A can be ca lcula ted since (19) {20 ) Although t-imny- differen.t str-~,ight litHH'l a.re 1,-:i-.o sst'ble with the ex:peri~enta.1 a.ate. , only one line 1"4f, S the correct dope where the sum of the r a te co.nst.1:1.nts is equa l to the negative o:f t he sum of' 9: and l, eerw.a.tion 21 . ( 21) The constavt~ c-"-ita ined by this method a re tabula ted. in Table II and it ca n be seen, that the rela tion above for the .stuns of the e0nstants che-c ks quits well. The hydroxy acid is added to the pe rchlorie acid in the form of a silver s~,lt, al!l.d since it 1a l a rgely unionized. in the strongly aci d. solution, a. correction must be made in t he hydrogen ion eoncentra ti on to e,ecount for the hydrogen ion concentration deereas:;e due to the :f'orm.a.tion of the 'Wlionized organic acid. t he h;y-d.ration constants, ~ 1 , used in t hese ... ? I o.-~---------------1 l t:>. , .. e ot c.f... tor 0\. r - e f?-C: pl ~on nt • (11 ) • e =0., 4 o. 038 _ 0 <K__ 0. 023 -_., ;f:f:.::: . l:, -~ !/!o e.g 9 • 50. -.fl o. 2oa 0. 268 Q o. 02i 0;1 e 0;05$ 0 . 053 0. 2 0. 1 @ r {_~-- {choun :ue) 0:.463 0.,994 0.'0l?Os. 0.094 0.-0l(lil s.,-sa Zt~ -2«41 2.,4.S z.s...s ..s 2..e 3-4 4.3. 2..9 2.,6-5.,5 1.. 000 1.1:0 1.85 3,.4? 9-ll 14-20 9-11 a._se K 16«-7 10.0 hrs. ·0 41,l:.7$5 9.,.8, cbG.-• hrs.. -c al0. t ~ Q._4,34 0,.,"2056 0~1202. 0.0000 0,..0442 o.0480 1 ..000 1.. 011 1.950- y~ Rela.tiw 0.140 - o.&9:1 0..,320 Q_. 32:i o.soo 0.,499 o.n, 0~180 0.,4'10 ·o_.01eoo 0.. 125 1.0 1.0 2.• 1 o.s2v 0.,01422 o._1626 0.0004 0,.1-4-"'10 2,. 1 Q..,2-2-8 0.,25S 0.12'7 ·0.,257 0.£00 o.as:9 o.02e o•.oaa o.ooe 0.,01 590 0 .. 01~ 1•.0 1.0 0.,526 0,.4-66 o.985 Slope 0.-..222 0"162 0.100 o.a54 0.- 00S 0,.;901 0,..24$0• 0,.1600 O,.,lSS:& 0,..0494 0.0361 -0.06..'36 o.sso 0.,5$4 o.. oos o.Jt-u- o.1ss ().,ZS$ 1Ee o •.3s6 0.207 0.22s o.~48 o.Qi93 o.~, (Ba()+) N 01 ca1cult;;tions we r e va lue£!. clete r mih~d f rom t he i ni H a l dopes of the hydr a tion e:rperiments co:rre etea. for t h ~ new hycl:rogen ion eoneentmtion. The constf'm t is !Jropo:rtional t o the hydrogen i on eonoentration. The time, !, is oor:reeted in e~ch ca se fo.r t he ave:r--a..ge time ef war mto ing/th(~ t hermosta t t empera ture a s det er mine d. by ei-b sc iss.a int ercepts of the plot of log10 f:.o/A! aga inst ! for t he hyd.ra tion of the unse.turated Gl.eid., Although t h is is four minutes :for the runs at lH.g5c it comes fact that when th~ solutions v1ere pl ace d in t h e t b.e:nnost~t an e:x:tr1c'l heil.1.ter i.•a s tu:rned on to help p rovi c'.e the h eat l'equired to bring the eole'i. solutions to tempe ra ture. A:pJ>arently. h"ll\.t was supplied fs.ster in the case of t.h~ ru.n.s at the highe:r temperature s . Since the runs ,tt one t empet'"'1 ture were :r.11 made at the same t i me, t he same t ime l a.g would occu:r fer all the rotes a t tha t tempera.tu.l'e . The poeHive intercepts. 0 .02. on the ord.i:nates of the :plots of Aif]o t:tga inst (~ a,t - .! ~') a re nea rly equ.-;.l in the d.iff erent r un s. This is due to the f a ct that a little of the sUver h reduced , since a slight amount of da.rk p reei:pi 1.Hit e form ed in the rea ction tube s . ?his subse q;ue ntly r e,i cte d du:dng b-romin~. t:ton to us@ bromine a nd. thus e Of aou.rse., mere dlve:r is rod:t;tced. in the t ubes which a re heP-. ted long~tbtit uniforin bromination of the srune amount of the free silver t e.kes p l a ce in each determina tion. .PJ. SI: ~'! l & ~ ~ § . --The coni;ta.nt s SI: and r_ c~.n be o'bt G>oined a lso from the :plot of !i/!o a.gainst [ <lh + 2:) .! li - (!f1 + j_) ~ Sl:J?.] . ~ This is a strai8ht line with the slope 1/(f;¼..., .@). However, t h is is not a s sensiti-ve to va ria tions in~ a.nd ! &s is t he plot from equation 16 for it 2 is sensitive only when the unsa tura ted a cid. hs s l a r gely dise.l)pea r-ed. Ho\.!eve r, these :points a r e t he lea.st a.ccu.ra.te . 7 shows the effect Fi g . t.- t of variations of .9: and ! on a plot of !}:_/Ao age,iinst [ (!;-1 + g) !. .&..! (.51 + !) .! a.tJ . - The same corrections in time a re made here as in the calcula tions concorn.ing the d.ehyd.ration experiments. the values of !!t a.nd ! used in t hese calculations. Table I c.ontains The slopes a nd the ealcu.lated va lues of 1/ (.2;: - j ) a re eq_Uc'<l to ea.ch other from the nature of t he point a t zero time. Since the unsatu:t-a.ted ac icl is a.d.de(l to the a qunou.s 1,,erchloric a cid. solution as such, it does not 11emove a.ny acid a.nd henc0 the v~lues of 21 and.! a re high.er here t h..~n in the oorrespon.dil'l_g dehya.rntion. runs \\!'here a lower hydrogen ion C,i:lncentr;ll.tion resulted from the addition of the silver salt of the org,;tnie a ci d. to the same p e.r ehlorie a cid. soluti on. For t he SJn.'3..ll d.i:ffe rences in the hydrogen ion Qoncentra tions in the hyd.ra.tion ,md. 1.ehyd.rn. tion runs the ve.lues of _g. and. Ji are :pro ... portiona.1 to the hydrogen :I.on concentre.tions of the solutions. Another check on the va lues ef Q and J! can be obtained from the -position of t he inaxima.. in the dehydra tion eurvBs. The maximum lies nt the :point whera the r a te of ehi;i,ngP- of the di,11ethylaorylic e.cid concentration is zero, e ~ue.tion 22. - d(f:./~) / d! = 0 ( 22 ) At the m.,;,.xi :mum , the v~.lu.esof the time is gi-ven in equation 23 . ( 23 ) Table II contains t he va.lue of !• obser"tred. l!),.!l.d calcula.ted. 0 for the ~xi.ma in the diffe-rent runs. The satisfa ctory ~greer.iont he!'et as well a.s the fact tha.t e~,ch Get of values of g .=.nd ! is satisfn.ctory (Tab le.s I and II) provM t ha.t the method. of treatment is r eliable. (),./.. o.o ~;,...i__.J...._.....J.._..L-----1.-...1....---1_......._ J. o: 0.01' E£teot ot van.at on 1n /Jl (_1t ~)_ i. ($_ on pl t 4<.C • (_,, t ~ - 0 fJ Cl (J) t !,/!::i:, ags.imre - tor bydratli (lft) = o. 80 h .,,g._ • ........... 0. .1.0 ),;1 (),1,) --tX.. .,1 !• T== 99. 5• • - #' o.o!'9 o;au, ( 0,.023 0.258 0. 02a . 0. 063 o._ osa o.1sa ,258 0.1 sen ftlue) deearboxylation constant obta ined above ie the apparent deoarbo.:qlation constant. ~ 3 • The value for the Uhca.talyzed reaction. 'lfJl.. ean be obt~ined from the slope of the plot of log 5?.o/~ against time, Fig. 5. 10 for the decarboxyla tion in a solution not conta in~ng pe rehloric ~eid. 6 R The cata lyzed decs.rboxylation constant, 15:r. is then tho difference betveen the apparent constant and the uncatalymed constant a t the same ionic strength. equation 2. decarboxylat1on runs ar '!'ha values of the constants for t he different found in Tables III and I V. Table III Decarbo xyla.tion Rate Oonstf.:.nts in t he Ab ence of :r·erehlo ric Acid. Del tive ~ /~ !fol a r o.o 1.0 2.1 0 . 0187 0. 0250 0 . 0237 0 . 0122 0 . 0157 0 . 0195 o. 775 0 . 0461 0 . 835 1.00 1. 24 111.85° 0.0 1. 0 2. 1 o.o 0 . 0202 0. 0250 0 . 0237 0 . 012• 0.0555 0 . 0720 0 . 002 1.0•_10 1.30 * j}, •.f.-Dimethyla cryl1o acid -- ---- -- -- -- --------- - - - - -(6) '!'he first five figures have been ·so formed e.s to :9r esent a.ll the experimental data available in an ea sily a coessi~le form without an axces sive number of plots and t ables. - -- -- -- ---- - - - - !U~~~ .QI ,gy~~ 1.QJ! 0 2 n ~ ~ ~n~ IeAt~ !t,re~t~ -21! .t~ ~<1Uim &a .Qcma,t ~nj; s l!;td,t,aiQ.1¼ J!t:t! Qou ~ . - -Aceord.ing to t he Ilrtsnst ed t he ory; the hyd~a tion ra te is expressed by equat ion 24 Usu.a. Uy the assumption is ma.d.e t hat t he activ ity eoeffioients of t he 7.>oaitive ions concel ee,eh. other. lfowever, since e,;,en the unionized !,!-di me thyl- a crylic a.cid a ctivity is a.ffeeted. by ionic strength . it is qu i te likely the,t the l a r ge :poeitiTe intermed.iat e coffl!llex i on a.l.o should be simi larly a ffected a.nd. thus 1 ts a ctivity c o<.1ffic1ent should b~ a funl'?tion of the ioni c strength di fterertt from t hat of t he hydronium ion. hen t he a ctivit y eoef~icient of va ter is caleu.la.t ed to decrease by about 8;{, when the solution is ma.de 2 norma l i n eodi um perchlora. te . a ll be grouped toi::.ether in the term . r Hence the 2, eti vit7 coefficient s may k • since t he individual a.cti vi t y -1 coeffie1en~s a r e not known well enot~ to be diseuu~d . The r 11.te then can be expressed by equa.tion 25. hydra tion r a te = .!>.' (H 3 0+)(Cal:1 0a ) Lk 6 _1 ( 25) where !si' cont ains the 1$\e r concentra tion, whieh is p raoUoa.lly the s.:·utH) the experimentally determined for the d.ifferent solutions, an!f'!_1 i:s !s1 1 (H3 0 ) k : :ia:xJtq1trb1to11bll7 £ ~ Indeed, _l, ..f. k a lr0a cl7 ha s b een sb.o\4i to be di f ferent. :f'ro.m the -1 a.oti Ti ty coefficient of t he unsaturated compound, t he hydration of ieobutene.7 1:here , the _£k ;...l / t, in the case of ..L unsa. • was compared with t he a ctivity ooef flc1en\ of isobut ene for different ionic strengt h~ a. a determi ned by di stri'bution experiments and found. to differ by 1~ and tJ.,O,; =t- a t 1on1 c st rengthn of l and 2 ! , r ,,., F.peeti vely. for the hydration r a te increa ses more ra.pidl)" with ionic strength than the act ivi t y of the butene . It a.an be Been therefore that the -ratio £,HaO -1::;,· RsO+/ ~ •H . RaO. H30+ must inc::-ea.se "'1 th ionic strength. 6 The activity of "18.ter actB in the opposite dir•~tion, hov.evar . decrea sing with increa sing io?lie atrength . !fherefore, the r atio must increase with ionic strength. J:::: 0+ / he- •er t~ . n The ~e most likely hold$ true for d.i methyla.0 ryl1e ~cid. The observed r a te conste.nt divi ded by the hyd ronii.m ion oonoentro.tion, ~ _,. k . .!5: 1 /( H3 0+), should. then "be -proportion .l to fo r the va rious exper.i ments n.re in Table I. ( IJ + , is t ak~r. '!io be the same a in compa:rin,g the 'l.'he V e lues of Jf 1 /{H 3 0+) T.ho bydrontum 1on concentni.tion. tho hydrogen 1on eonoentr~tion. y_ a t different tempe ratures. there -.- ~l t he r a tios of L,!s 1 to the L ~ 1 r e a lso t abula ted a t ionic strength of 1 . 0 !! and hydro~en ion conc entration of 1. 0 ! a t t he s~me temyeratur~ . det ermines t he Y.k --1 L J 5-i .of the ret;;ction r a te constant . This is t e rmed It is f a irly eonetant for any one solution over t he diffe:rent tempera tures . the rell¼tiVe This ratio in 'V':lrioun solutions rela,tivo to a. standard f k in l 1'! hydrogatt. ion concentra tion a nd l ! ionic strength . the rala ti 'Ye l~s a n a id ff@et of t he different 1on1o strengths and :1lydrogen ion concentrations on l'i g . g shows tha t J:: k value.a cf the hydra tion constant for !-olut1ons of -1 hyd.rogen ion eonoentra tion appro.xina. t ely 0 . 5 ! , i~oraa se rapidly a s t he ionic strength increases . The rel.ative ~ 1 r a ising the ionic e.trength :f':rom l to 2 !J. ls r,;.lmoet doubled by The inere ee of £~1 1th' ionic strength ha.s also been observed in the h.yo,'t"t1,t1on of other unsatura ted eompounds~ 1 • 2 •7•8 - ... -- ----. -- - - - - - ----- ---- - -- - -- --- --- -- - ~ ~ ~ + 4ngoA30 . a30 a3 1-· // ,. fa ,"' $ • ¾ I J.f - /?. e. IC, lt-ve $ _YA(),.,- I. ' I- I :JJ.o I J,~ I ..>.Jo I I I "·"' I I I 1,1.i. '-1~ I 2.,, \, ~ Plot ot r l tt ,4 again t 1oni.o etr ngth t a.ppro ion Rel t1t - ntratio · _c:·k tox- lfydr. t tely . 5 - Dehydration !a id oat '.\yt art:iji·at on o uncalta.1¥ d ) - a • 5" 99. a 111. 0 .... ¢ ., • + '-()-- -fr fJ r:O p • In the r e..s,etions carried out ~.t the same ia,ni,c str,,m gth but ~t different hydrogen ion concentrations. t he ;replacement of hyd.r-0gen ion by sodium ton inerez,.s~s t he values of the relative r a te. £ -kl of the reaction This is due to the speci:fio d.if:ferenc$ of the tw.o ions in their This difference in aetioJl. ef'f''a ct on the activity of dimethyla.J:rylic acid. ha e been noticed chiefly in oxygena.ted o-ompoud.s., erotonaldehyde. crotonie a ci d. , and rlimethyla.orylic acid where the oxoniu formation is a:ppreeia'ble. A more extended analysis of these t:11f f ects in other sya,tems is being :aad.e. r e.te constant is simile.r to that of the hyclration ?1-'l.te excep t tht,,t troi.ter does not enter tha expression, equation 26. dehyd,r-a tion rate = ls.s 11 (H30+)(0.nH1o03) x ·~,.+ ~ 1 ~ • QP no O !. /~ H O 1-, O+ ~ o ~7 ~Cs 10 3.u3 t rom assumpt,ions eq,uivalent t ri those ll'IF!.d.43 £0:r the. hydra tion r a te, this red:u.oes to the a: r.:;p:res.=ion dehydration r a te ' where ~a 1 (H 3 0+) = ,!:a 1 ( H3 0+ ) ( C6Hio0a) L1/ k (27) _;a L k = ,!; a s exp erimentally meae'U.l'ed.. The values of 3 -2 // '!f, 3 / (H 3 0 + ) , wM.ch a :re <:l.ireotly p roportional to .t_ lsa, are t2.bulated in Table II along with the rela tive ~_m k va lues for the different s olutions. The latter values a.re plotted in Figure 8 to show the variation of the relative Lk ....:a with ionic strengt h c:~t approximately 0 . 5 lf . &1. hydrogen iot,. conce.n tration of These varia tions e.re 11uite si mibr to those for the hydmt1on e:ir.:periments a.e are t he vsi.ri~,Ucns oocu.rr1.ng ~then hyilrogen ion is re:pla.ced by sodiu.m ion. of p erchloric acid must t €.ke r,l ace by t wo m®Chr.1 llienrn, one a.ci <l catalyzed a.nd the ether not. The fr»ct that this is a t:t'11s b.y c'troge>n ion ea ta.lysir,. is indi c.?.ted b;r the f a.ct that the clece..rbo:r.ylfit ion r a te in 0.51f (26) :perehloric a.cid ie four times tha t in Wl:',ter, whereas the change in the eon cent:ra tion of the unionized /:i.Cid (KA e 10- 5) is only 2 :percent. 0 The uncatalyzecl deca:rboxylation rate. ]s3- , is itself a function of the ionic strength, 1!'able Ir:t, a.lild t he r efore the hyrlroxy ...e.eid cs.nnot deea rboxyla te by itself. .Eith er the a ci d must react with water or the anion mu.!:!.t deca rbo,:-..y).e.te . If the l a tter is the ea. ae the r a te constant, Q k; 3--, wo1.ud be ~ function of the ionic strength l'!ince d.issoci$ t10n and hence the anion concentra tion a re a lso functions of tha t quantity . An experiment to test the dee-arboxyl a.tion of the a.nion W'd. S e.a rried out Table IV Deca.:r'boxyla tion Consta.lit s of !-Hy-d.roxyisova.leric Acid in Ferchlot'ic Aci,l Solutions ot) µ Normial ~ial _k a_l H ht· ~ . -1 J. r • • 0. 0337 H Relative (!~30!fi) ~i! k -. ......,3 g50 1.0 0.0494 0.528 o. t~66 l.O 0.0361 2.l 0. 0538 0.994 1.0 1.0 2.1 0.196 o.9s5 o . 03t1,2 1. 00 O.GJS6 0.0735 1.13. t; .14o 0.141 1.00 0.096 0.182 0.324 1.2, 0 . 0204 0. 0343 2.15 g50 0.527 0.1.~63 0 .152 0 . 222 0.150 2 . 30 by heating ~ eoncent:ratt<l solution o:f oa.leium j_.....hydroxyisovalerate at 100° for 3 days 1n a. s~led t ube . Since no t ertiary butyl alcohol was formed. , the a nion cannot be the materia l which deca.rboxyla tes. •rherefore, the unca taly2:ed decarboxyl~.tion mechanism mu.st be the reaetiQn of t he unioni zed acid with wat er. The :Bronsted GX'pre s sion f or the r eaction of ft-hydroxyisova ler'ic a cid with wat e r is given by e quation ;~8: cleca rboxyla tion rate == 0 ~3- ( C U o0 5 1 3 ) = 'l!~Q (S20 )( CsHa 0 0s) • LI! o 2 fa • H ( 28) o / L,y.10 u . o tLQ 5 10 3 8••~ 0 'l'he a.Gtivity coefficients a nd. hence the observed r a te constant, la-, a r e f unctions of the ionic strength . In Table I V a r e shown t he deca rbo~ l a tion const ants , obser;red a t dif fe rent ionic strenP,:ths. hyd.rogen ion concehtra tions and t empc➔ 1·atm· 0a . '!'he d.e ca rooxyl a tion constant fo r t he a cid Cs?. t a lyzecl ro?.-,Ction , .!s:rR . i s a.ctua,,lly t he difference betwe en t he obse rved co:n s t a.nt, Js 3 , a.nd. t he constant a t zero hyclrogen ion concentra tion, 'lsaQ, but a t t he same ion:l.c strength, neglecting t he cliffe:renee in t h e effect of a h ydrogen and so di um ion on ½./J.. of the ilnCt9.ta.1 y·z t:Hi rea ctio11 . The :Sr6ns ted equation fo r t he a cid cata lyzed deca.rboxyla tion is simil a r to equation 26, the expr ession for t he dehydra tion reaction. Th e -val ue s of ~}1 eorreeted for. the hyd~ogen ion concentration a nd also the vc,lues of the re l.a:bive r ~'J! for 3 the different solvents a.:re in Table IV and Fi g . 8 . It ean be see:a t hat t he se values are somewh.-a.t grea ter t han tho1:1e tor the hydration and dehydration rea ctions . 1he rela ti~ely low effect of ionic strength on the u.~ionized decarbo:cyla tion rea ction is due to t he f act that t he othe r ca sas deal with positive ions and it would be reasonable to expect a l a rgel" effeo t of ionic strength .on ions than on EHe.etrieally neutral substa nces . would, doterinine the final concentrations of the hro organic a cid$ if deca.rboxyle.tion ';Jere not taking pace ca n 'be oa.lcula ted ,:;. s the quotient of the hydration and dehydration ra te constants. These values a re in strength on the dehydration a.nd hyd.:rati-0n re.te constants a re essentially the same with in axperimenti'\.l error . ~hu.s there is no the different tempera.ture s . tb.e plots of 'Ii/he log10 ,!f1 a.gs.inst tb.o reeipro-eal of the a bsolute t empera.tu.re ( n,g . 9) . The a etiira tion ener:gy is independent of ionic strength and Arrhenius e q'l:tattion. In Table V a lso ~ r 0 t he valu.-e s of t he heat of hydration os lculate.d r~s t.he ,11fference betveen the a ctivation ©nergies of t he hyd!'f.ition and. effect t".lf struc:t uxe on t he h.Ha t of hydra tion will be mao.e i.n a ftttu.re co1nmunic;1,tion . 9 ( 9)'.t'e.ble V of b.:,-6ration :paper nu.mbe:r • U of t;he t 1:t,:rcm,-:a.l dtt,.t a eon.cerning t he he-a t of hyd.r u.t :t cn <;f crotcmic a.eid should. r ~ad (1;:"'") l . Ot, 2. 06 j:i 2. 06 2. 06 ---- -~l>,H k:eal . Hem.ts of act ivation Si Q,,, ...,,,,, 20 .1 20 . 2 25. 4 25.6 5.3 5 . J;~ - - - - - 11emp . coefficient 90..100° }tyd , Dehyd. 2 .11 2. 12 2. 57 2. 60 Thus the heia t of ~yd.rati on of cro_tonic acid. is 5 . l-1- kcal. instea d of 10 .. 1 kca.l . as pr~viously stated.. This~0.6 k cal. lo we r than the h~a.t of hyd.rei.tion of' e r otonaldehyde r tither t han l~ kcal. h i gh.er . Since it has been shown that Qne woul d. e::r.pect eroton.aldehyde to lose more resona:nce ~n®r gy than crot on.i c aci d in the hydra tion reaetion t he small differenee in the heats of hydration ef the &:l dehyde a.nd a dd. mU.$3t be d.ue to another pr0pert7 of t he ca rboxy1 and. a lclehyd.~ groups which would decr ea se r e lativel y t,he heat of hy<:lra.tion of' the aci d . rhia ma:v 'be_ (lua to the . ~..._" "~ • . different inductive effects of ,_carboxyl and oorcbeny:t;:. This :problem is be i ng invasti&J,ted :ftlrther with .r e speat to va:ri,ou..a other hydrati:on r ea oti ons, Table V Thermal Const ants of t he H:yclr~ti,m , Dehydration a nd Deca rboxyla tion Ror..oUcns ( H+) _)}:_ Si No:rm;.:l.l Nor mal Fi g . 9 kcal. keal . kca.l . s2.45-99.s5° l .O 1.0 28 .l 0.5 1.0 27 . 4 0.3 1. 0 27 .5 0.5 o.6 2. 1 28.2 . o.6 o.o o.o Average ~ .S:1. 0 5i3- kcal. 99 .s5-111 .s5° 26.s 34. 7 30. 2• 33.s 26 .0 33.6 31. 2• 35.3. Afr -O f hyd'.r'ation kce.l . 27.7 Pemper0.tu..re 0oe:e'ficient for 100-110() . -7 q..,. 3 ' 1.0 - - - - - - - - - - - - - - - - - - , , 2.. ..., ·' 0 ~-=-- 0 '? ,.... '-' -> --.... 1/T Plot o log1~ &E;li'.il,ll,Dt· 1/! tor th• byllr tion o~f-A.ll"~wtby1a eyllo ao14. (ll 0 (I • 1.·000 o. 544 o. 48o butyl a lcohol with the formation of i ~0butm1e i E inf<l:ppr,3 ciable even at 111. 85° since a t equilibrium t he concentra tion of t he a lcohol is 100 t imes th.a t of butene if t he heat of hyd.r a tion in a1;1ueou.s solution remai ns const an t at 11. 6 kcal. since t he equilibri1.mi eonsti?.nt of {0 4 :a: 011)/(C.Jlg ) 9 is 4000 a,t 35°. 1 odor. The :p resence of 'bu.tene in the W:!.por i Ei evi denced by its 'f he butene conc~ntra tion in the Wit.po:r- ithen the tube h opened. is very l ow a.nd. is ealeul.s:.ted. t o be of t he nrdiail' of 0. 2 mm ., for most of t he butene in t he vapor a t the hi/di te.mp ara t ur@ would hyd:rat.e ,s.t r oom tempe rature before the tube wa s op~ned since it &"!. $ been sh.own.7 that in 1 ! nitric a cid bu.tet1.e hyd:ra.tes 90'.\t 1.n one-ha l f hou:t a.t a temper oi.tu.re of 25~ . A ca lculation canno t °i:>e ma.de as to the frrc. . et i on of t he system in i;h.e V3.:por ph,~se since 1t would be ;proportir;n.i.l~l to the vo l u."tle of tl1e ~:pace above t he solution which varied :f:t•om 1 t o 15 ml. In ,~ny case the a.nal;rses of the 1.~d.fo~::ting t ha.t the butt!ne eHher hyirated. on eooling (II' was lo ~t :i.11 t h.e l)OU.Ting of the solution ,.,nd. tho 'butyl a lcohol J?l'(:lsent did not bromi na.te,. .-...Acoord.ing ~C~E?: ~ - - - -- - to Ge:rhk:e e:.n<:1- Willra,th, :to - - - - - - - - -- - - - - - - - - -. -301- -(19c::'9~ - - -• ... - • • (10) M. Ger.hke and. E. li . Willra th, Z. -ohy sik. Chem . • ~ f - hydroxybutyric a cid lo si.es water t o form a. conr9 ound of lower fr<?.¢ ca rbo xyl content, a. O.l mol al solution a t l OO Q h;; vi ng 11-.5% of the. ca rboxyl group s bound . It h.::. s 'been shown tho.t if the f.orrnr-i.tion of a. 7. lactone is the aau.se . dilut ion would h ,.;.Ve no sfi'act on this va.lu.e.-1 1 Prom the stabilizing effect of methyl groups on eir.s.11 ringl' o:ne ,,:0uld (ll) C. K . Ingold, Ann. Report of Chem. Soo., la, 1,27 (l.925). e xpe ct 1!- l a otone formation to be f a vored in f-hy!iroxyiso~lerie .aci (l over f -hydre:xy}mtyl'ic acid . The formation of t h e li:i.ctone would:. inor ea. s-e t h$ values !S:! &.nc. .!a for dehydrati on a n.d deca.r'boxyla tion . Si.nee t he small change would. roughly be the aame ;fo:r the t wo tempera tures it cancels out in the i mport.;,.nt ea lcula.tiol/1 of the hea t of hy<'Lration. A:ny bimolecula r esterifica.tion would be negligible a.t t he high dilutions prevailing . . ---! ,,e-d.i me thyla.a ry li c a cid wa e. p repa:red .§.,-..@.- ~ according to a modification of the method of :Barbie r and. Leser 12 from the chlorof o:rm rna ction of meeityl oxide . Into ~ lit er of 1. 5]: sodium hydroxide isoluticn wa.s pa.sseo. in 185 g . ( 2. 6 mole) ~f chlorine t,rith. ccoli~g. an d tc this 75 g. (0 . 77 m~l~) of me f- ityl oxide (F.astw:i.n lod&.k Com:pany })TO<h1ot r~dfa t illed t h rou.~ Vi greaux c olu.ran a nd 'boiline a,t 125- l flSi> unCGrr.) wa s a d.de d with vigorous me oh&nica l stirring , a t first i n a. steady stream until a.bout was t;tdded. wh ich brought t he r eaction mi xtul"e to t h e boiling 1,1oint under a. r eflt:t.X. The r0-st wa s ~tld.ed. d.ropwise to maint a in t he t empera ture about Go e>-. ?here w~s n◊ r esi dual hypoohlorite . 11'.he a.queous solution wa s neutri'l,lizecl with 300 ml. 6 ! suJ .furie a cid a nd. then a cidified. with 200 ml. more . diox ide va s evolved... At fir s t r;, l a rge n,mount of cmrbon A white oil separ a ted and crJstallized on cooling . The mother liq_ue,r wa.s extr§'t Ctea. with four 200- ml . portions of et her. The resid.ue on evaporation was combined with t he origina l c ryst.'.lls and t he mixture recrystallized from hot water y-i el ding le.rge individual needl e-like er.y $ta1s. Yield. WI:'.\. $ 30 g . ( 0 . 34 mole). ti4i . Th e crysta ls we r e r ecrysta llize d a.ga in from h ot wa t or . ?i . F . ""66 . 5... 67 . 5° corr. Analysh for unsatura.tion by- bromina tion ehowed. 1. 02 doubl e bonds p er. mole,. from d.iacetone a leohol by t he chlorofo rm r eaction. Tq a, solution of 320 g . (8 molos) o:f sodium hrd:roxid.e in 1. 5 liters of water i,m,s a.acted with cooling, 230 g . (3 . 1 moles) of chlortne, an-d then 100 g . ( 0 . 85 mole) of 1H a eeto.n e al~ohol with vigo rous sti rring . The r ea ction mixture becan.t$ hot and the chloroform di stilled. out a.a it wae formed . The eUght exces l!'. of chlorine i12.s removed by !i!Odiun1 bisu.lfi ta e-.nd. the solut i on wa s <teoomposed W'ith 125 ml . of 6 ....N su.lfu:r.tc ;:;,ci d . The sol ution w-as e:&tra.eted with e ight 1-liter portions cf eithe r l:td.ch we:re subaequ.ently extra cted. with a th.in J)a.ste of 20 g . c-alcitun hyd.roxide in 200 ml. w&te:r . The lime ext:re,ct was a.nute d. to lJ.OO ml. , filtered , a,nd. carbon.?.te<i -until the solution was ;,Just :n~ut ~ l to phenolph'tli.."J.lein. A. clear solution was obtained 'by fiHerini ft- hydroxyhova le:ra te sa1;,a:ra t ed a..ft e1· concentra tion to 250 ml. 1'.lheie we i ghed 9 g. { .03 mole) vhen a,:d.ecl in va.cuttm ove r ph o s~,horlc anhydri de a t 70° but were cont aminated wi_th chlori de. O,n ad.ding the e~.lcj:mn sa lt to silver .§_.. hydr oxyisovalera. te p r e ei:p itB.t~ d i 1!lrM,1,;.i,'!taly . To t h e iui xture 3 g . of "hyflowl'I . . , as ad.ded, a nd. the ::n.ix tu:re fil t ared ho t. The li ght grey- crysta ls which se-par 0,t1zd on coolinit were fil te:ired. off i~nci. the origin():,l precipita te of t he silver sa.lt 1r..a s e~tra.cted twice more witli. the mother liquor . The con1bined ei-ysta.ls of t hree 9u.ch extra ctions (only ;.., little pr e cip ita ted t he third ti me ) were :recrysta llized out of 500 :nl. boiling wa t er . The soli d. wa s I;- veiry light grey. The c:ry st.;ll s ...,,re r a q_u.ita sta1)le ~ Calcula ted f or C5H9o3 Ag , Ag , 45 . 1;:; J!' o u.nd ("by Yolltarcl /•.nal. method), 48 . 0% . of different a c i ci. ity were made merely by a,d_d.ing d.ifferent a.mounts of solid sodium hydroxide to p ortions o-f concentra tion . i:-1 perchloric a ci d s.o lution of known 'fb.e cha ng,e in volume caused b y this ;,. d.dit1on waa neglected. :r,re eorreetion -was applied for t h e effect of tem:pera.ture on the itOlTume since the change in volume from 82 to 110° is. only 2%. con$ta nt is not affected by the volume chruage . The equilib1"i.um Thl, ae solutions then had t he s-ame ionic strength (within 2% ) bl1.t <:li:fferenj(',,. a cid concentra tions . a eid solutions were made up to appro1dmate oo:noentra.tion with standard. perchlo ric: a cid and analyzed voltw1et:rica lly by bromin.::~tion . !-Hydroxy- isova.le:ric a cid solutions were mac.le u:p to exact volume with the perchloric a cid solution from a kno-wn weight of silver ! ...hyd.roxyisov.alerate . 15.00 ml. a.liquots of these solutions we-re pipetted into test tubes with constricted necks and sealed off . '!'hey were then :pli!>,,ced in an oil thermo.- stat a.t temper@;tures c:>:f' 82 .45 ,± .05°, 99.s5 .:t .05°, or 111. 85 ! .05° . Tu.bes were removed a.t different time int e rvals e.nd. quenched in iee water . The tip of the tube '1/aS broken and t he e-0ntente washed into the flask used. for analysis. The tubes in the l at ter pa rt of any one run showed a n appreciable p :ressure of carbon &ioxido and. evQ.lved a very slight odor of isobutene on opening. tj~t!1.Q.d ,g! A n ~ .--This we.s essentia lly th~ same as th.at d.escribed. p revi ously . 3 The 'bromin ation of the !1:f- d.imethylaorylio a cid. took pla ce a s ra.:p id.ly a s bromine w. s liberat ed with the result t hat bromina tio.n 'lfra s complete as soon a s the bromine color appeF.:.red . That the bromin.ated product is stable is shown by the f a ct t hat t he ana lysis does not change when 125f excess bromine h 1n·esent for 5 mirrn.t es after the first app<il8il"ance of the bromine color. The ~- hy-drozyisova.leric acid seemed to substitute about 0.5% when brominated und.er the conditions of the experiment. a crylic ac id wae m:.~de up by dissolving an approximate a.mount of th'e soli <l in pure water and sta.ndard.i:dng the solution volumetri~lly. Soltttions of the ,!-hy(lroxyisovalerie acid were m-a<le by adding a 1"..nown a.mount e,f t!le silver salt to a n exaotly equivalent a.mount of :pe:rchloric acid. solution. The :reacti.o n wa.$ carried out in sea.led. tu.be$ $intilar to that of the The solutions were o.nalyzed. by titr~tion with a. st$;:ndard. dehyd.rlil.tion. sodium hydroxide solution to the phenolphthalein end point with boiling to remove carbon dioxide a.s the end point was approached. The silver ion wa s first precipitated by the addition of 5 ml. o:f' one-hal f satur$.ted sod.ium chloride since otherwis-e silver hydro:x:id.e would form before thtl} :phenolphthalein end :point ~s rea-ched. l:" ive gr am.:§1; of i .,a-dimethyla.crylie aeid and 20 :ml. of 2 1! :perchlo:rie acid were sealed in a tube a.nd heateo. at 100° for 20 hcurs. :releQ,sed from time to time. seemed to be sepa.ra.t1n_g. The pressure '11.'3.S A.t the end. of tha.t -period some light oil The aq1.1eou.s pl:l.e.aa was separated.. neu.treliz-ed. to :phenol:phthalein with sodium hyd:rexide and th.en disti lled. The first :portion of the distillate \..n?.s satur.a.ted with poh.ss.ium ea.rbona.te and the 1 ml . of oil which separa ted was dried with the ca.r'.Gonate. 30 . 0 ° u.ncorr . The boiling :point wa s When 0. 25 ml. oi' this tilubstance was mixed. with 1 1 / 2 ml . 1 HCl-Z:n0l:a rea gent. 3 9. 25 m.1. of a second oil which boiled at 50.i(unco:rr. - -- - - - -- . - - - - - - - - - - - - - - - - - - - - ~ was obta ined. The constants in t he l i te r a.ture for tertia ry butyl a lcohol and chlori de a.re 82 .9° and 51°, re spectively. Tha oil which separated in t-he origina l :reaction mixtu.re probably wa s polymerized isobutene for a similti.r oil was observed to sepacra.te when 5 ml . of tertia ry bu.tyl a l cohol and. 20 ml. of 2 ! :perchloric a eid were hea ted unt'.ter similar conditions. !.tt~~ ~~tleo~~l! .2l ~UllJ ! -Jitii~sgyal..,~ ~ .... -Twenty ml. of a n aqueous soltttion containing a bout 10 gnins of calcium !-hy,lroxyi so- . vale:rate were heated at 100° in a sea.led tube 'for 60 hours. The mb:ture was d.istilled through a 2 ft. Vigrea:ux colu.mn with a reflux condenser. Only enougit ~lcohol was present to give the first few drops a faint odor of tertia ry butyl alcohol but no alcohol separ a ted on sa.tw,.-a,ting t hese d.rops with potassium carbonate. If the ion decarboxyla.tes, ~ne would expect essentially complete decomposition, even under milder conditions • ..s ~ The e.oid. ca talyzed hyrlra.tion of lh~-dim.ethylacrylic a cid to ! ... hydrox.yiscvaleric a cid was inve sti ga.ted in aqueous p erohloric acid a.nd sodium pe rchlora te solution$ of hydrogen ion concentrations varying ±"rom 0.3 to l.O ! and ionic strengths varying from 0.3 to 2. 0 j at temperatures of 82. 45 , 99.s5 and 111.i5•. The a cio_ ea talyz.ed. dehydration of ;El-hydrox;risova.leric. o1, ~id to Q&- dimethyla.crylic a cid was investigated in various pe:rchloric acid and sodium perehlora.te solutions a t 99.85 and 111.BSQ . The interpreta,tion of the cl.ata of the hydration a nd dehydrat ion rea ctions wa s complioo.ted. by the s-ilitultF.i,neous d.eearboxyla.tion of the _fl;hydroxyi sovaleric acid to form tari.fo,ry butyl a lcohol. The a cid ea t 2.lyzed decarboxylat.ion was inveetie;&.ted under the s...l>i.me conditions a s the a cid ca t a l yzed dehydra tion. A mat hema.tical treatment was develop ed to hati.(tle a system of rea ctions of the t ype A ~ :a -'-7 C , where t he r eaction r a te const a nts a re comparable. The a.cid ca talyzed hydrat i on, dehydration ~nd decarboxylation rea ctions are f irst order with respect to t h e organic acid co·n centra.tion a nd first ore.er with respect t.o the hydrogen ion concentra tion. The rea ction rate coI;l.sta.nts of these t h ree rea ctions incre&se rapidly with ionic strength and. slowly when scodium ion repls ces hydrogen ion a.t constant ionic strength. The unca t a.lyzecl d.eea.rboxylation of Q.-hydro:xyiso-mleric a.cid in distilled wa ter a,nd in aqueous sod.ium perchlora.te solutiens was in... vestigated a t 99 . 85 and 111 . 85°. The rea et:ton is first order trith re spect to the organic a.oid. The constant is somevma t smaller than the con$tant; moderately for the a cid catalyzed d.eca.rboxylatio:n, and. inere..a.ses ~ with ionic strength . Decarboxylation involve s the free acid and not the a nion . The rah of deqarboxyli~tio.n of .i ..h.-dimethylacrylic acid. in pure wa t f,r is negligible eon1pa.r e d. to that of .ft-hydroxyisovaleric acid. The hea t of activa tion of the hydration of f,!-dilllethylacrylie r.ci d e ssentia lly is not a. function of ionic strength or hyd.rogen ion eoneentr;'l.tion. For the hyd.ra.tion of di me thyla.ccylio ~,cid., t.iH correct value for crotonic acid is--5.4 kcal. is ... s . 1 k cal. The ·'.l.G The co...mpounds e.nd da.ta which .::re ava ilable from this thesi s u:nd t he work of previous investigator s fo r & discussion of t he effect o:r str1.:.cture on the heet and t he f-m tropy q~antity,:1 of activation for the lrydrat io:n: and dehy-dr e.tion :r.-eaetions and on the heat end :e ntropy change i n the hydrat ion reeetions a.re in Table I. 4...1_,1-dimethylacTylio ac i d dif:fe1·s from cz•otonic acid by having e. I se eond methyl grour, in ti ,e beta pos1tio11.. Its hef<lt of hyd:r ation 1s 2.6 .hydrogen en.cl henee its pr esence on the bE,ta oe.rbon ato1'/1 would r e l at t vely stabilize a positive ehe.1'ge 011 t1'1at e t oo1,. ..:hi s woul d increase the conjugation energy of the double bond with the ce.rhoxy-1 group and would t end to decrease t he beat of hydration of the dimeth.yl.aorylfo acid. {b) Alcohols are s table a eeording to the order te!'tiary ) secondary ) prin:.acy. Si:noe the -product of hydrati on. or ,umethyl ... ac:rylic acid. is e. tertiary o.leohol wh:ilH the.t of crotonie a:eid is e secondary alcohol, t h.e former should tend t o evolve more heat on hydration t hen t he let ter. (e) The starie eff'eot of a methyl group cis t o the earbcxyl p..,roup may als o eontribute to t he gree.te.r hee.t of h~rdration of dimeth.ylacr:rl:tc aeid. Cis crotonic add is less stable i ta heat of' hydration would be greater. Since di:i:nethylecry lie aeid is similar to eia erotonie acid wlth respect to having a methyl group and a oarbo:x:yl group on t he same side of t he double bond, it is quite probable that this contributes to the difference in the heats of hydration. The a.-hydroxybutyric acid Crotonie acid Dimethyla~lie acid Isobutene12 Crotonaldehyde 5.,5 - ti H k c o..1 , 20.1 25.6 11.. 9 9,.9 3.39 4.07 0.0148 O.165 0.88 56. 1230 (1934) 16,.,3 0.0022 21.a ' 7400 1.,43 12.5 19.9 a. s. Winstein end H. J. Lucas. Ibid•• ~,1451 (1937) 1. w. 11'., Eberz and H. 1. Lucas. :t.A.C.80 :4-h.vdroxyisovaleric ac14 a.1 26.9 :55.0 19.7 14.9 Tert .. butyl alcohol 11.6 23.3 34.8 21.4 11.a 6.3 18.2 24.5 21.5 11.6 Aldol Hydrate Unsaturate Table I 18 dHferences in the other thel"'!:",odytu3.m1c quant1 ties for this patr may be du~ to similar. considerationfil. Dimethylo.crylic acid is similar struetu re:11-y to :tsobutene in that both have branched chai ns a.t one end of the molecm.le and both h¥drate to give tertia!'Y alcohols. However• the former has a carboxyl group in place of a hydrogen atom and the difference between t he two groups may exert its effect in th:ree ways: (a) The eloctrom.erie of.feeta on the oleftnic double bonds are dif':f:'e!'~mt. (b) The electro:meri.e eff'eats on the hydrated molecules are dl f.fo rent, (c} T'rte carno;cyl group Qan resonate with the douhle bond . The combined effects, a and b must be less than or in the same di r~ ction ar. the rcsoI1an 00 ett'eot > f'or the latter alone wou.ld mnke the heat ot hydration of th e oci<l less than that ~"):r 1sobutene and th:l.s is what is a ctually observed,. C:rotonaldeh~rde is similar in etruoture to crotonic aoid exeept tor the forr;zy-1 group in place of the car'bo:r.yl group. The di.f1'ereuce :tn the effE'½cts of thes e two groups may exert i teelt in thr•ee ways 1 vJJltch ~n:•e similar to those listed above. However, both of' these groups ea.n resonate with t:1e ca -;;).f'in.1c double bond, but the resonance energ ies a.r e 111-.oba.bly different and would thus cause e difference i n t he heats of hydration • .As ha s already been pointe d out {pg . 7), the· d:lfferenca in the eleotro- nef!ativity effects for the two must be greater than the differenee in It is interesting to note tha.t f,?r the heats of activation o.t the dehydration reeet1ons the value of 26 kcal, holds for the compounds with a secondary alcohol group but a value of 55 kcal. holds if the alcohol gi·oup is tertiary. 'l'here ar e not enou~..h dete available at th&Pt"esent tim.e to perirJ.t a JllOl"G: extensive discussion of the eff'eet or etrueture on the terms concerned in the kinet1.es end them.od;yna.m1es ot the hydration and dehydration reactior.e. 50 A study wes r,,..ade of the kinetics and thermod:ynernies or the reversible hydration or erotonie acid to ,l..Jniydroxy-1:H.ityrie aeid and ot r'.-•µ_-dimethylacrylio aeid tot~hydroxyiso~aleric acid in dilute aqueous perchloric acid solutions or various 1onic strengths and hYdrogen ion concentrations. Both the hydration end dehydration reactions ere first 9:rder wtth reapect to the organic acid eoneentr~tion and the hydrogen ion conoentrat1on. The first order reaction rate constants for the organic acids 1neree.se with 1on1e strength and with the replao.era.ent of hydrogen ion with sodium ton. The crotonic acid reaehee e stable equilibrium but the hydration of dimethyl ... acrylic e.eid is complicated 'by the decarbozylation of the i£_-eydl"oxyieovs.leriQ acid. The equilibrium. constant for erotonic acid is 5.oo et 9o.o0 and 3.28 a.t 111.3°. '!'hat ealeu.lated for dimethyle.orylie aeid if deearboxylation .· · O were not taking :plaoe is 3.4 at 99.90 and 2,.4 at. 111,8 • The heats of hydration ot orotonie aoid end dimethylacrylic acid ere 5.5 and 8,1 kcal. respectively. The deaarboxyletion ot (ll-b.ydroxyisovelerie aeid was i11vest1ge.ted in water and dilute sodium perohlorete solutions with e.nd without added perchlorio aoid. The reaction wee found to proceed by two mechanisms. one was a,cid catalyzed and the other was not. The rate of the acid catalyzed deoarboxylation increased much more rapidly with ionic strength than did the uncatelyzed reaction. , 51 Propositions l. Although optically active 2-bromo-5-hydroxy butane raeemi~es upon conversion to the 2,3 ...dibromobuta.ne with RBrt it is probable that pentane l~ould :aot raeennze upon conversion to the i.5 ..dibromope-ntane. S,. Winstein a.nd R,. J., Lueas t J. A.-n. Chem. Soe • .ll• 2845 {1969). 2. The apparent heat of activation of the reaction of unsyn'IJ]letrieal ethylene dibromide derivatives with potassimn iodide in methanol solution should be a function of t be temperature .. 3. Contrary to the statement of J .. B, Conant and G., B. Kistiakowsky that "the effect (on the heat of hydrogenation of ethylene) of pregresaively substituting the tolll" hydrogen a.toms by methyl groups is not additive" the ef'feet can be shown to be add:l.ttve when consistent correction terms are induded. Chem. Soc• !!, 1:37 { 1936) • 4. The heat of aettve.t1on of the dehydre:tion of tertiary' amyl alcohol is probably less when trimethylethylene is the product than when methyl ethyl ethylene is the product. H. J. Lucas and Y. Liu, J'. Am. Chem. Soc. .!?!• 2158 ( 1934) • Y. tui and We i, J. Chinese Chem-. Soc.!• i?.97 (1936). F. D. Rossini and J. w. Knowlton, Nat. Bur. of Stand. J". of Res,. 12., 249 {1937). - F. D. Rossini• ibid. 13, 21 {19M). Propositions (continued} 6. The relative eleetronegativity order of a aeries of organic radicals according to bond moments es ta'bulftted by n. c. Brown is not valid. H,. O. Brown ,- J .. P.m. Chem., Soc ,. .fil.• 1483 ( 19$9) • 6,. It should be possible to deter.mine the relative acidities of trariOu.s organic compounds such as alcohols~ malonie esters, and aeetoacetic esters from ki net ic data concerning t he reaction rate of the sodium salts of the above with an alkyl halide. "• The l ow hee.t of dimerization of benzoi e acid r elat ive to that of formic a.c~d acetic acids is reasonable from a resonance point of view., L. Pauling, "The Nature of i.he Chemioal Bond"• Cornell Univ . Press, Ithaca , N. Y., 1939; p. 187. A. S ., Coolidge, :J. Am. Ob.em. Soc. E.Q., 2166 (19 28 ). F . H. :Vieo.:Oougall, ibid • .E.§.t 2585 (1936). e. The heats of combust ion of various iaomerio aldohexoses may 'be correl ated wlth their structures. H. M, Bhffman and s. W•. Fox t J • .Am. Chem .. Soc • .§.2.• 1400 (1938 ). - 'I'. H. Olarke and o. s. St egeman , ibid, 61 , 1?26 (1959). 0., $, Parks ands. B. Thomas, ibi d,.,~• 1423 {19:34). A. We issberger , J. Org. Chem.!• 245 (193?}. 9. The explanation by Buswell , Dunlop, Rodebush and s.wart:r. of the ultraviolet absorption spectrum of aged aqueous acrolein solutions is not valid, A. M. Buswell , E. c. Dunlo:Pt W• H. Rodebush , J. B. Swartz, J' • Am. Chem.,. 800 • .§&, 325 ( 1940). E,. E. Gilbert and J, j,. Donles:vy, ibido .fillt 1911 (1936 ). J. V. Nef, Ann, i335 , 219 (1904) • 53 Propositions {continued) 10. When lethal su.bstanees are oompared by tests on living cells, the :relative eonce:ntre.tions wbieh kill the stame fraction of the cells in a standard, time ia often taken as the inverse :ratios or tbeir potencies,. not valid when a substanee being tested is unstable., This measui>eis '!'he true relativ~ letha.li ty may be ealeulated by the appHeation of e. factor eonteiniI?-f't' the decomposition eonste.nt of t he unstable p01$<>n, K:ronig and Paul.• A. f. Uygi ene • !,g_; 1 ( 1897 ) o. Oross, Biochem. Zeit., !!,t 550 (1910}. R. Weino.11.ng, Phytopathology _!!; 1155 (1934) • 11. The fact that the observed lethal aot i vi ty of gliooladi'tlm f .im'b:ria.ty.m toxin toward rhizoctonie $Olan! is a constant when tested at a pH ra.nse of 5. 5 to 5 .. 0 but decreases with increasing pH at other -veluea of pH may be expleined from t he known properties of the toxin and the groi>1th of fungi. R. Weindling , Phytopathology, ~• 1153 (19M). 12~ Definite courses should be devoted to the htll1l.anitarian side of chemistry, 54: AO;rmowtEDGMENT I wish to make known my appreciation of the aid and eneouragement Professor H.J. Lucas provided in the pursuit of this research