The Decomposition of Di-o-Tolyliodonium Iodide Citation Kennedy, Edwin Russell (1934) The Decomposition of Di-o-Tolyliodonium Iodide. Master's thesis, California Institute of Technology. doi:10.7907/7da9-yc49. https://resolver.caltech.edu/CaltechTHESIS:09202024-181837097 Abstract No abstract. Item Type: Thesis (Master's thesis) 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 1934 Record Number: CaltechTHESIS:09202024-181837097 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:09202024-181837097 DOI: 10.7907/7da9-yc49 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 16748 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 24 Sep 2024 21:21 Last Modified: 24 Sep 2024 21:29 Thesis Files PDF - Final Version See Usage Policy. 5MB Repository Staff Only: item control page

'::H..ii .D..... Co. POSITION O ... I-o-TOLYLIODONIU IODIDE Thesis by E . Russell .r~ennedy In oartial fulfillment of the requirements for the degree of :r.:aster of Science in Chemistry California Institute of Technolo ·y Pasadena, California 1934 .. yontents of this Thesis wo possible mechanisms are postulated for the thermal decomposition at 150 of di- rtho-tolyliodonium iodide. The most likely involves ta) the decomposition of the o-Tolyliodonium ion into o-Iodotoluene and positive o-Tolyl ion and (b) the uniting of this ion with the ne atlve iodide ion to 0 form o-Iodotoluene. ~he reaction pro-ucts of this decomposition we~e converted into Toluic acid by the Jri an· s'10 of t1is n to be ortho-...,oluic aci - . '· he 0 ar· re ction ost i, )o.,.,tant aspect ecoffiposiGion is tie exis~ence o~ a ositive o-~ol~l ion . o-Iofotoluene Tuas prepa~ed and converte" into o-Iodosotoluer.e. ':h means o oxi a,.:,ion o ioc osotol 10ne to iodoxytoluene by hypochlorite tas studied. new method of preparing iodonium compounds was applied in the preparation of di-otolyliodonium iodide. The conversion of iodotoluene to toluic acid using small quantities •as studied . ':'.::z DEC • P00ITION OF DI-0-'T'OLYLIO O:;IUL IOL ID• .. hen c i - o- tolyliodonium iodide undergoes therIT'.al decomposition into tolyl io"ide t~e product mi~ht be either a mixture of the ortho and meta isomers or else the pure ortho isomer alone , dependin 0 upon whether the reaction~took one of the two follow ins courses; ( a ) rearrangement, followed. by clecomposition, or ( b ) decompositio:1. into ions, followed by combination '.)f the ions. The two ossibili ties are shmm below: ( c...) REn, RANGE:..ErJT FI I II '11 III IV V VI ( b) D.t<.,C0KP0SITI01r FI ST + 0~-0: VII I - _.. 0 1+ VIII 0:+ Q\ r- - IX X O Ht hen an clectro· .. e__:11t,ive r dical is .... ttac'·1eQ to a ni tro3en or oxy -en atom directlJ linlrno to a carbon atom of the benzene rin~, uolecular rearranse~ent is usually possible by the migration of such a radical to an ortho or para position in the benzene ring . 3ince in gene ral the oxygen compounds undergo rearrangement more readily than the nitrogen derivatives it seems reasonable to assume that the more electronegative the atom to which the mir:rating radical is attached, the more readily rearran ement will take place. On such a basis alone , one might expect a migration of the iodide iodine atom to a position in one of the benzene rings ortho or para to the iodonium iodine atom . The compound represented by formula II above would result if para migration takes place . ueconposition of this intermediate would lea(. to the production of a mixture of 0-iodotoluene (III) and m- iodotoluene (IV) or to a mixture of toluene (V) and 2,~ - di - odotoluene (VI) or to a mixture of all four compoun..:.s . 11ere is so11 e a oriori evidence for believin~ t~at such a rearran~ement is not li':ely since t'1e two io'ine atoms in "': . . e .iolecule of ~itolylioc_oniur:i iodide are not joined to each other by a covalent bon,1. '.:'he compound is a salt anC. has tl1e follov:ing electronic structure ~ + - .. . . .I I )n t'1is basis t'.e 2i ·ration of iodine to the para position would appear to be as unlikely as the migration of chlorine in phenylammonium chloride . If di -o-tolyliodonium iodide suffers decomposition in the second series of changes above, then the positive di - o-tolyliodonium ion(VII) must decompose into o-iodotoluene ~ -III ) and positive o-tolyl ion (IA). Provided the latter undergoes no subsequent change it would then unite with the negative iodide ion to produce o-iodotoluene (A). The product in this case would be pure o-iodotoluene . determination of the nature of the reaction products would make possible a decision in favor of one of the two possible mechan isms~ !.any years ago Heilbronner 2 ,investigating this reaction, concluded that di-o - tolyliodoniurn iodide was changed into ortho iodotoluene, which was identified by conversion into nitro -iodotoluene . Since no statement appears in regard to which ni tro compound v:as formed nor the amount obtained upon nitration , it is quite possible that other reaction products might have been present in the reaction mixture and yet have been overlooked by him . In the present research the iodotoluene produced in the decomposition was converted into the corresponding toluic acid through the reaction of carbon dioxide upon the tolyl magnesium iodide , The resulting acid was definitely shown to be pure ortho acid . This result confirms the conclusions of Heilbronner, and of vfilmot3 who d.id some 4. work on this problem, and indicates that the decomposition proceed8 according to the second mechanism given above . The most important aspect of this decomposition is the existence of a positive ortho - tolyl ion . OUTLINE OF PERI VH~,;i, T.i: L PROCEDU. ◄ CH Ct 2 HNOg ICl2 'NCl KI HCl Toluidine O O :,11, Diazonium chloride NaOH 0 0 NaOCl :plus Heat Iodaxytoluene Iodosotoluene 0 0 012! Iodotoluene 02 0 Iodotoluene plus Iodosotoluene o~o iU Iodoxytoluene o 3 •gl __ c_ o... 2_~> Tolylmagne$ium iodide Ditolyliodoniu□ 0 hydroxide 0 150 Ditolyliodonium iodide CH ,. Iodoxytoluene Iodosotoluene Iodide dichloride > :H3 .,__k_fS---#> Iodatoluene 0 OOiugI O COOH Toluic Acid 6. EXPERII,_ENTAL Part I The preparation of Di-o-tolyliodonium iodide A. The preparation of pure o-iodotoluene . The starting materia l for this s tep in the sy~thesi s was o-tolu ioine, CE 3c6H NH 2 . This material was purified of 4 other iso11H?-l'S E•.eco:e,~. ing to t h6 r,, t l;.c, ,~ cf J:c::'..lstein 4 . The procedure was as follov,s: 400 grams of o-toluidine was dissolved in 800 ml. of 6N nitric acid. The solution was filtered boilin5 hot anc1 e..llowea to c ooL 'l'he fine crystals , 1h.i ch f'o rned were filtered off and redissolved in the min- imum quantity of boiling water, norite decolorizing carbon adde d and the s olution fil t ered hot . . f t er cooling t he c r ys t a l s , which were l a r ge purpl ish pl ates , were f ilt e r ed. of f and the mother li quor used to l j ssol ve another b·~ tch of o- toluiCine nit r ate ,repared as aJove . The crystallization 1 as continuea u~~il ea ch b_tch had been recrystallize& three times, usin...; the mother liquor from the first batch to crystallize the secon·:.i h .:.tch in each case. The crystals were sucked dry on a filter and wei ·heel . Iielcl was 9.:,2 ;rams ( 77 . 31; of ori3inal t oluid i ne ) . The toluic' ine Has freed fror:l t:1e nitric acid. by a'l2_inc; 2::0 ,~rams s odium hydroxide ( slight excess ), together with enou~h nater to diss olve the sodi nitrate formed , and the mi xture sub - mittec1 to steam distillatii. on . :'he toluidine waz t:1en separated frorr, the aq_ueous phase in the dist i l l ate . The proC:.uct tnus obtained was colorless , but s l ov1ly became r ed over a lon 6 period of time due perhaps to oxidati on by oxycen of the 7. air, action of li 0 ht, etc. o-Iodotoluene was prepared from this toluidine by the diazo reaction , using 10~; sodium nitrite eol.ution ( to which had been added a small quantity of sodium meta bi sulphite to reduce any nitrate present) . The end point of the reaction was determined vlith starch- iodide paper . Upon adding potassium iodide solution to the diazonium solution the iodotoluene separated as a dark oil . The o- iodotoluene from the first three runs was combined for the purposes of purification . It was rapidly distilled at atmospheric pressure . This treatment left an oily black tar in the distilling flask . (probably cresol) . The oranse colored distillate was washed in a separatory funnel as follows: 1. NaOH 2 . raOH 3 . H2 o 4 . HCl 5 . HCl 6 . H20 7 . Very dilute aOH 8 . H20 9. H20 10 . H2 o. This c;s.ve a clear oily lic..ui, sodi ·1hich ·Has drieC: vith anhydrous carbonate and vacumn distilled at 24 mrr. . The product was a colorless liquid "lhich was kept in a glass stoppered bottle filled with nitrogen , as otherwise a pink color develops on standing , due to oxidation . B . The preparation of meta and para iodotoluenes . s i t was later found necessary to prepare meta and para iodotoluenes , their preparation will be includec ~ere for the purposes of co.parison . , -Iodotoluene ·.,as prepared. as above fro m- toluidine . , hich was obtaine,· fro,. ..eta ni trotoh~e 1e. The ru - ni tro ~ol- 8. uene was purified by three crystallizations (m.p . 16 ° ). The m-nitrotoluene was converted into m-toluidine, = ~~e action of tin and hydrochloric acid , followed by eutralization of the acid and steam distillation . m- Nitrotoluene 75.0 grams m- Toluidine 53 .5 grams l91 . 5~) The p-iodotoluene was obtained from ~astman ' s practical p-toluidine . Table I contains the results of these preparations. Physical constants determined for the compounds are in Table :::I . 1111 "' ~ i I " p ~- ::l. TIO: IO LU"'""'"'E Io ot.olu . . . ne T lui ine r r ,~ 'U": ,.J - ~i"'anl' ,r aS cru e "'e istille 1 . ortho 0 5 (CJ) 2 . ortho 125 21'"' ( 1::4 ) 3 . ortho 1.25. 209 ( 147 ) 1, 2, 3 . 300 512 361 59 . 1 4. ortho 83 138 1. 5 5 . ortho 60 100. 82 . 0 o . 1 eta 35 -4 . ..., 76 . 5 7 . para 50 76 . 0 74 . 6 ,,.. T. BLE I I 1:- P,JY 'IC. L CONST L ':S IO DOTOLu.1£. Iodotoluene ortb.o . 745 L.i 205 . 5 24 r.im 95 . 5 B. Sp. Gr . 0 ..... p 210 .0 para 0 1 .7090 1 . 6030 nl) ~"' 20/20 metn 1 . 6012 34 . 5-35 . 0 0 .. 10: C. rhe prep~ration of iodosotoluene CH v~~,i 3 4 o-Iodosotoluene was pre:pared from the purified o-iodotoluene by a slight modification of the method of ,, ille._)erodt5 . . solution of iodotoluene in anhydrous chloroform (dryed by means of calcium chloride and distilled after seuaratin7 .__, off the solid) was made up in the ratio of 2ml. chloroform to one gram iodotoluene . If a more dilute solution is used an unnecessary amount of chloroform is wasted as will be seen, while if a more concentrated solution is used it becomes difficult to stir wit:1 a consequent failure to secure complete reaction. Chlorine, dryed by passin~ through two concentrated sulphuric acid wash bottles and then through a tube containing phosphoric anhy rid...,, w-.,.,s led onto the surf ce of the solution in a closed flabk and vigorous stirrin: a)plied to cat 1.se solution of the __,as. ( If the ...,as entr;y tube di9s "below the surface of the solution it very quietly plu~s up). The flask is coole- ~urin the ~acsa~e of the ~as. ,hen the solution is satu ate~ with chlorine (in 1 a tout 2~- . olu s), it is placed under vacurim and practically all of the chlorofor~ evaporated at room te.perature . The remaining chlorofonn (about 10% of the original) is sucked off from a filter and the dry yellow crystals of iodotoluene dichloride placed in a mortar and rubbed with a solution of sodium hydroxide ( 1 gram i~a H to 8 ml . H2o) in slight excess of the amount calculated according to the following equation .. 11. The iodosotoluene is filtered off, washed with water and chloroform and dryed. The purity wa etern:ined by iodimetry according to a method developed by ., ilmot 3 . ':he dist in ..,ulshins feature of this method is the adcition of as ,all quantity of chloroform at the beginning of the titration reaction, otherwise the solid iodine compound reacts but slowly possibly because its surface becomes coated with reaction products which are insoluble in \-Yater but dissolve in the chloroform. ~y saturating the alkaline filtrate from the preparation of iododsotoluene with sulfur dioxide and/or adding a s all amount of potassium iodide a small quantity ( 3-51 of ori __ inal iodosotoluene) may be recovered . o.f -i-ort'10tol ·lio oniu io, ice . .:i 12. T BLE III -,.· P~EF..- '.I.: TION OF IODuSJTOLU~IL.:s Iodotoluene grams Iodosotoluene ,rt gra ,s /0 1. ortho 109 83 71.0 2. ortho 50 41 76 . 5 3. ortho 70 51.7 64 . 0 4 . ortho 90 70 73.0 . meta 20 16.3 76,0 6. para 25 17.0 64.0 _,('." note: The yielc to a very l a r ge extent depended upon the amount of chloroform rejected in the separation of iodotoluen-: this solvent . c· ichloride, as it is quite soluble in 13 . 'I BLE IV * AJALYSI OF IOD)5u':"'0LUE Sampl e O.lN.Th io. Found 11.:. 6rams grams Strength_ I~ .:) Dr yi ng Proc edure 1. ortho 0 . 156 12 . 49 0. 14:S 92 . 8 36 hr . in a ir 2a ortho 0 . 345 26 . 80 0 . 313 91. 0 2 days in air b 0 . 0995 7 . 90 0 , 0924 92 , ,.... 9 d ys in air C 0.231 19 , 65 0 , '230 99 . 6 2b i n vacumn 12 _-ir. 3a ortho 0.068 5 . 42 0 . 063 93 . 2 4 cays in air b 0 . 08 1!-7 7 . 43 0.0870 102 . 5 "3b in vacurnn 10 hr. 4 . ortho 0.379 0 2.81 0.337 89.0 1 day in air 5. n.eta ,.. o . para 0 . 380 29 . 05 0.340 89 . 4 1 day in air 0 . 207 1:5 . 46 0 . 181 87 . 4 2 days in air This data is interpreted to mean that when iodos ot oluene is dryed in air the compound obtained is CH 3 c €1 (OH ) 4 2 , which compound corresponds to 92 . 9io oxidizing strength when calculated as CH C H I o . On vacur.m dessication 3 6 4 the bonded water is lost and the iodosotoluene obtained . Since iodosotoluene slowly decomposes into iodotoluene and iodoxytoluene , removal of the iodotoluene will result in a com1)ound. of apparent 01~i.."izin5 strenc;th :reater than lOQ, ~~nee tho iodoxJtoluene has twice the oxidizin~ ctrea~th on a molal basis of io? soto luene . Thus the value of 102. ~: a' \'J"C indicates a purity of about 97. , . . .) -Por -tr c. , "' V L • ~as ma e to use a -odification of u.t bJ . ,il~ot . 1 consisted in .i~inG iodosotoluene and pure calcit , ' ypochlo i te with ~u t, ei1ou '...hin paste :.:m:i assin carbon ~~ioxide slowly into the mixLure witl stirrin~. If t _ ~a- as asse· lJ ~Jo~)~ chlorine ;as for eC in the reaction mixture . The reaction usually required \ o to t1ree ys for com~letion . The reaction rr: ixture Y.'e.s washed with lE nitric acid, with 'iater n.nd. •with chloroform. The purity of the iodoxytoluene ·•as deten.1ined as before oy iodimetry, calc,Jlatin_; the oxidizing stren th as ctt c 6H4 ro 2 . Yields were calcu3 lated according to the followinG reactions: Ca (OC1) 2 + H 2co 3 2 ctt 0 H Io -t- 2 HOCl 3 0 4 2 H61 + Caco 3 7 Caco 3 + 2 HOCl 2 CH C H ro tt 2 co + 3 6 4 2 + CaC1 3 2 HCl 2 CaCl 2 The results of several trial runs are presented in table V 15. M• . o ic.:t Ci 7 ro .._;r . 0, I .~;- i ~:: -¼-- V _,~ I:Iypoch:orite Ill )lS 4 a (001) IO_ 0.;;JTOLl.J..:.,_,E CO Btirrin 0 time cl.ays 2 1. 10 2. 10 4 Oa(OC1) 2 in 4 lJts {;' 3. 10 1 ra Cl, 1 Ca( 001) 0 4. 10 :::> • ,- 10 6. 10 7. 10 4 Ca( 'JCl ) ' * xi 'izin strength,.; 0 83 t:.... 2.1 20 175 2 3 .7 35 148 3 ,;,'. 1.9 18 78 ,_ '- 1 .1 NaOCl Yield :..:,r . ,.J 22 ') ➔~ - r.POC'!Lv IT,Z 2 .3 2 -~~ 2 ;;'{ 2 1.5 NaOCl in 4 pts ~ Q 3 .5 33 95 no 4 4.2 40 99 1 . 5 I:7a0Cl no 2 3.7 36 97 15 extremely sloH Recalculation of the titration data on the assu ption that the product is CH c6H Io 3 4 3 or CH 3c6H4 ro 4 6 ives the values shown in Table VI . From these calculations it seems and #3 is largely CH C H ro or a 3 3 6 4 3 4 mixture of CH c 6H4 Io and CH c 6H4 Io 4 . . t present no further 3 3 3 as if #2 is CH C6H4 Io '11 BLE VI -:, CALCULATION OF OXIDIZING P01.8R CH 3 C6H4-I0 2 CH 3C6H 4 ro 3 CH 3C6H4Io 4- /f 2 175 124 99 #3 148 105 83 data is available rega rding the cornposi tion and structure of t hese compounds . s may be seen from Table V the yields are lo¼ and the oxidizing strength of the product depends largely upon 16 . the experimental conditions. For this reason it was decided to use the standard procedure for preparing iodoxy compounds , which consists in heating iodosotoluene with wate r. • further advantage of this method lies in the fact that iodotoluene steam distills out of the mixture and may be recovered . It was found possible to recrystallize the iodoxytoluene from hot wa·'. r . In one such e--peri· .ent the followin5 data were obtained: Iodosotoluene grams Iodoxytol~ene ·1/, grams ,v 19 . 5 50 38 Iodot oluene grams % 16 . 8 Titration data- CH 3C6H4I0 2 sample e;r. O.lN Thio . ml . found gr . strength 0.219 17 . 09 0 . 214 97 . 5 /o 36 drying procedure 2 days in air 17. E. The Preparation of Di-o-tolyliodonium iodide . Two attempts were made to prepare this compound by the method of Leyer and Hartmann 7 who reported yields of 93,; for phenyliodonium iodide . Equimolal quantities of i6dosotoluene and iodoxytoluene were treated with water and an excess of freshly precipitated silver oxide by agitating in a glass stoppered bottle for t wo days . After filter i ng off silver oxide and any unreacted material,~, o :iltrate was reduced with sulphur dioxide , but only a negligi bl e pr ecipitate was obtaine d. In a similar experiment using a smaller quantity of water a precipitate of ditolyliodonium iodide was obtained which corresponded to a yield of 18~ of theoretical . It was decided to modify the procedure somewhat and the following was tried . 9 . 3 grams (0 . 038 mol) of c7H7 ro 2 , 9 . 0 grams {0 . 038 mol ) of c7H7 ro , 10 ·rams (0 . 043 mol ) of silver oxide , 10 ml . of chloroform and a small quantity of water were ground together in a mortar . At intervals the water was poured off into a flask and more water added to the mixture in the mortar. Fi nally the pasty mass remaining was left to react overnight . The collected aqueous portions were filtered and reduced with sulphur dioxide which caused the immediate forrJation of a hite precipitate. A s□ all amount of potassium iodide was \ 1 added to ensure the complete precipitation of the co. ound. The prec ipi ta te as '"'il tereC:. a.1C. washed vii th ua ter and alcohol . ::ielc.1- nas 7 .0 ~rar..s ( 4L~.v, ) . u:110:. ofo~ H .... 0 a because iv Has thou.....,ht that it would aicl the reaction b e 18 . cissolvin· vater-insolu;.:,le L.ter-.u.e-.:.aue .... rod c . . s. r:i _ e a· ove proce ·ui-"e uas repea·~ed wit 1 t'1e except ion that only ~ J of the molal quantity of silver oxiQe was used . '.'.:he yield in this case was practically the same as before ( L:.3 . :,,;) . This rould seem to indicate that the silver oxide acts i:1erely as a catalyst and is i1.ot required in molal quantities as is usually i-•eported. The fact that the yield is but 44;; as compared to 931J for the phenyl coi, pound mar possibly be attributed to the steric influence of the methyl group in the ortho position . None of the investigators who prepared the o-tolyl compound reported yields . F. The Preparation of Toluic cid from Iodotoluene. ·erore preceding with the decomposition of the di-o - tolyliodonium iodide it was thought advisable to deten.~ine the conditions necessary for an optimum identification of the products by conversion of the iodotoluene to Toluic acid by the Grignard reaction. Accordingly pure iodotoluene was dissolved in anhydrous ether and slowly run onto ma~nesium in anhydrous ether with stirring . fter sufficient time for complete reaction,carbon dioxi4e , dried by passin~ t~rou5h conce1trateu sul~huric acid and then over phosphoric anhy -.ride, was passed in •1i th external - coolin~ of the reaction flask . lhen no more carbon dioxide was abso bed, ice anC::. a 100✓', excess of 6N sulphur•ic acia. was c 'fed . The ether phase aqu~ous phase extracte 1a$ sepa!.,ate ~ off and the with three successive portions of ether . ~, e combined .ethereal phases vere extract.el wi t:--1 four 19 . suceseive ;,ortions of 2N soc...ium carbo:1.ate solutio:1 in t'.e r_.t::.o of 4/2/2/1. Tl'le coffi'i.)ine ~ so ium carbonate solution extracts ~·ere heated to remove dissolved ether, coolecl and aci ifie with C.P . sul:r,'1uric acid. T._e ~recipitated '.::oluic acid was dried a.1 wei hed . ::-o loss is introduced b so2.- u· ility o~ Lhe toluic acie in water as the solubility at room temperature is less than 0 .04 ~ram per l00t1l . The results of several such runs are'shown in Table VII . The extracted F TOLUIC tCID '.:'. BLE VII -.. ·_HE IoJ.otoluene ?, l. ,. v r,.ols ate of stirring ther cone. Toluic aci l'l/ _r. gr . 1 i) slo\ 49 1 . ortho 10 . 4 1 .0 2. ort.10 , 8 . 2 1.0 12 , 2 2.6 3 , ortho 8.0 1.0 27 . 5 2. 4 47 moc.erate 4 . ortho 2 , ..) 1 .0 8 .2 2,2 42 II 5 . iodobenzene 1.0 6. 4 52 fl 5 . raeta 8.2 1.1 9,8 44 fast 7 . 11eta 6 .1 1.3 16 . 1 47 moderate 8 . ueta 6.7 1 .3 12 . 0 1.6 38 JI 9 . para 6. 1 1.3 16 . 0 2.1 55 ti 10 . ortho 11 , 3 1.2 5.4 77 " \ fast (note: iodotoluene added very slowly in # 4) ether solution was evaporated and th~ thick semi - solid oil obtained 1s · thought to be 0-0 1 -ditolyl (L . p . 17 . 0 0 ) . It was first thou ht that the low yield ts~ould be of order of 00 couplin JJ ) fo.r iodobenzene) was to be ascribed to reactions of the Grignard reagent to form ditolyl . Changes in the experimental proc~dure designed to reduce 20 . this coupling reaction ~ave no better yields. twas next thou3ht that the low yield was due to the steric hindrance ·of the methyl gro_u p but experiments with iodobenzene , Ii.eta iodotoluene, and para iodotoluene showed the same poor yield . I t was finally concluded that the lo'iv· yields were caused by the presence of minute quantities of water, since it reacts with the Grigna reagent . i calculation showed that the presence of 0 . 1..., gra:!l. of water ?, ould lower the yield by about 50/4 on the basis of the quantities used . _ethyl iodide -was placed in the flask with the ma.::_:nesium.anc . ether and allowed to react for an hour . This reacts in a similar manner vith water as does iodotoluene but much more rapidly . ~he toluic acid preparation was then carried out as before . mhe result of this run is sho~n in f/10 above and the yield was maY'kedly improved and compares favorably wit. the literature value for iodobenzene usin::; much lar~er quantities . The methyl iodide a~:ed ,as just that arr:ount to re:..ct 'lith the supposed vater prese1.t. o 1 '..:.e ,,all o t 1 ap:p r tus, J i. ,ute amounts in t.:e ct.1er, t-tc . .~nr excess of .et:1yl .io-i'e ui:~ for-4, uc~ ic aciC:, and there is also the possibility of the forlliation of xylene wit~ iJdotoluene . Theoe experiments also shov' that the three isomeric lodotoluenes react with equal facility to fori toluic ~ci~ un-er the,e con..,..itione . ""his observation len"s stren3L1 t1e conclusions 'rawn later re 0 ar in· the identity of the 'ecm... posi tion prod..1cts of i-o - tolyliodonium iodide . -J 21 . ? t II m, cc~ Juition of ~i-o--olyliodoniL PrelL1in"rJ e:xneri._ents s'10,·e -'-.)1~ lio oniu that the 'i-o- io ide d.id not ".ecompose until raised to D l~O . In carryin out the ~ecoLpoc~tion 16 . 38 ra1s were placed in a 100 ml flas''" proviue • with a reflux c-ondenser an 0 i ..r:iersed i11 a glycerine bath at . l~_,, . After about t ·o r::inutes "ecor.rposit:.on set in an' v1as co.,plete insi_:e of five secon s . ~here was a loss o:' wei~ht of 0 . 11 ur ms o~ ·eco .poui ·ion anu this rr: ., be attribute '.:,o the lower e _• o C, the c to the . . r io.1 ens r . a· ou..... 'T'' f 7 oul - h v ;• r v , ll ~ram , o • e \( :c • lu •77 out o"' J_ _ .;_.., ·eac :on - o uct and coll c~ no li. i • ran bac . There was a s..: ll ount of io"ine vaJcr in the flas~ . The ~eco~position pro- ~ct , -:,rans.:'...,red to a __;lass g ei__,hin 0 pipet . r o atteri.1pt wi s · !l. e ~o puri~y the product . Part III r e I ~enti:'ication of the .1..ecosposi tio._ r.:ihe in6'3X of refrc_ction ,;as deterrr.ined . l , u07 'Le ~ree iouine \las d.eterminecl. by titrat:.ng r.ith so:iurn thiosulphate solution . :r . 1 .183 0 . 0 ~4 r:'l:::'._o . r.J l. Iodine ::;r . i.J 0 .004_ 0 . 38 .. 22 . 14 . :r ~r.(O.O66 in 1..., ~l. of an .. rous et· er three iours 01to 1 . 8 o . . et or (w'1ic1 .ol) of the dee mpJoition product 1 : as r~n ~uri : ~.(0 . 074 ~~e course o: ol) of - . nesiu. in 70 1. reacted for one hou' .,ith 0 . ..,0 .1. nethyl io iue) containe~ in a 200ml . 3-neck flask provi -ed wi t'1 a mechanical stirrer, reflux condenser , and separatory funnel . The st,irrinc:, uas continued another three hours . r.i carbon dioxide was passed in for three hours with stirrin . 1he acid 'as extracteC:. as described above , , dryed in a vacumn dessicator , and weighed . i- ielc vrns S , h gr . (O . O42 ol) or 64,~ . The rude a iC:. melted ·at 102 . 4-103 . 0 0 L.lixture of t1is with or~ho-toluic acid (obtained in the above tripl runs and recrystallized from hot 1.a~er. x .P. 103 . :., - 163 . 7 ° ) elte" at 102 . 5-103.0, ... ilea aci~ ( ... P. 110 . -111.~ ixtu.r,., . r 0 ) e ,it' o .el te' at U:J-91 , an it- para-toluic acid ( u.P. 178 , J-173 , " 0 ) 1 a eta-tolu.:.c i: ture elted at 5-14 0 This indicates that the product v.c.s pure ortho-toluic acid . hen the ether solution from which the toluic acid ad been extractecl was evaporated l....,] grams of a pasty oil was obtained . If this be calculated as ditolyl it represents 3 . 7 ,.:;ram or 251; of the de c ornposi tion product . This brings the decomposition products accounted for to 89% - Circumstantia evi1ence• may be presented to show that this oil was formed during the gri 6 nard reaction rather than durin~ the decomposition of the di-o-tolyliodonium iodide itself . Briefly this evidence is: 1 . I f ditolyl were formed in the decomposition 23 . there , ould be an equivalent amount of iodine set free . The amount of free iodine actually shown to be present would account for only 0 . 04 gr . of the 1 . 55 0 r . found . 2 . This oil resembled in physical appearance those byproducts obtained in a similar fashion from uure orthoiodotoluene . 3 . The refractive index of a 1~, solution of the oil in o-iodotoluene was: 1.592 (Decomposition product nn 1 . 607 o-Iodotoluene nD 1 . 6030) Thus the addition of the oil changes the refractive ·index in the opposite direction from which it should change to coincide with the decomposition product . The isolation of ortho-toluic acid unmixed with other isomers shows that ortho-iodotoluene is the sole product of the decomposition of di-o-tolyliodonium iodide . I wish to express my deepest thanks to Prof. H. J .Lucas, who su ) )ested this problem, for his continued interest and advice . 24 . uU, ...i ,,hen RY i-:,-to 1 ..;lio onium io i 'e un er~:oes t e1"L al 0 ecompasition at l~O it is co~verted into o-iodotoluene. This was established by converting into an acid Hhich was shown to be o-toluic acid. The rcost li 'rn ly wchanism of t 1e reaction involves la) he deco~position of the tolyliodonium ion into o-io o- toluene anC:. positive o-tolyl ion and { 'i) the uni tin· of this ion 'vith the ne:ative iodide ion to fom o-iodotoluene . The oxiCation of o-iodosotoluene by aqueous hypochlorite was investi 0 ated . new method of preparin iodonium compounds is described . The optimum conditions for the conversion of io otolue,1e to toluic acid in __;cod yield when workin3 with small q_uantit,ies as investi 1 . . ~ro a a er to be p li -e u er tDe sronsorship •. J. ,.J ·c s ') f eil" 0 r. r' er .' 2° ' 191:: t 1es.:) ilrr.ot , Ur. er~ra ua te 1::heJis ~·.I. 'I' . 3. -:'I ¾. Beilstein , vol. 12, 5. •illecero t , Ber . , 2 ~, 360( J.S93) ~ t ...930) . 4 , p.773 ,, i lle3ero "t , :.e r. , 22,, 1:::;6°( 1 "96) 7. ~:e er an( :artmann , Ber ., El_, 426 , 502 ( 1894)