An Improved Synthesis of 2-Nitro-6-Aminotoluene Citation Rosicky, Fred George (1949) An Improved Synthesis of 2-Nitro-6-Aminotoluene. Master's thesis, California Institute of Technology. doi:10.7907/8nyx-ge59. https://resolver.caltech.edu/CaltechTHESIS:09242025-191121445 Abstract Aromatic fluorides have been prepared and known for a long time (1), but not much work has been done with them until comparatively recently when they have assumed considerable importance as starting materials for the preparation of fluorinated ∝-amino acids. A considerable number of fluorinated ∝-amino acids have been prepared. during the past fifteen years, chiefly fluorine derivatives of phenylalanine (2), tyrosine (3,4,5,6,7), and thyronine (5,8). Fluorine derivatives of tryptophane have to date not been described in the literature. The compound 2-nitro-6-fluorotoluene was desired as a starting material later to be used in an attempt to synthesize a r1uorine derivative of tryptophane; hence this work was undertaken in an effort to achieve an improved synthesis of the nitrofluorotoluene. 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): Niemann, Carl G. Thesis Committee: Unknown, Unknown Defense Date: 1948 Record Number: CaltechTHESIS:09242025-191121445 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:09242025-191121445 DOI: 10.7907/8nyx-ge59 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 17700 Collection: CaltechTHESIS Deposited By: Ben Maggio Deposited On: 04 Oct 2025 12:49 Last Modified: 04 Oct 2025 12:56 Thesis Files PDF - Final Version See Usage Policy. 7MB Repository Staff Only: item control page

.Al\f D /.IPROVED SYN'lli:ESIS OF 2-NITR0-6-AMINOTOLUN~E Thesis by :!!'red George Rosi cky In Partial :l!'ulfillment of the Reg_uirements For the Degree of Master of Science California Institute of Technology Pasadena, California 1948 ACK1'J0WLEOO-EMENT The author wishes to thank Professor Carl Niemann for his invaluable assistance and advice throughout the course of this work. TABLE OF CON1 ENTS 1 TITLE ~ PAGE I Introduction 1 II 2,6-Dinitro m- and :p-Toluene- 5 sulfonic Acids III 2,4,6 Trinitrotoluene 6 IV 2,6-Dinitro-4-Aminotoluene 7 V 2,6-Dinitrotoluene 9 VI 2-Nitro-6-.Arui.notoluene 12 VII 2-Fluoro-6-Nitrotoluene 13 VIII Discussion 15 IX Summary 21 X References 22 - 1 INTRODUCTION Aromatic fluorides have been prepared and known for a long time ( 1), but not much work has been done with them until comparatively recently when they have assumed considerable importance as starting materials for the preparation of fluorinated G(-a.mino acids. A considerable number of fluorinated ~-amino acids have been prepared. during the past fifteen years, chiefly fluorine derivatives of phenylalanine (2), tyrosine (3,4,5,6,7), and thyronine (5,8). Fluorine deri va.ti ves of tryptophane have to date not been described in the literature. The compound 2-nitro- 6-fluorotoluene was desired as a starting material later to be used in an attempt to synthesize a r1uorine derivative of tryptophane; hence this work was undertaken in an effort to achieve an improved synthesis of the nitrofluorotoluene. Van Loon and V. Meyer (9) first prepared 2-nitro-6fluorotoluene by treatment of 2-nitro-6-hydroxytoluene with gaseous hydrogen fluoride, and by conversion of 2-nitro-6aminotoluene to the diazopiperide which was subsequently heated with dry hydrogen fluoride and potassium fluoride. This synthesis is only of academic interest, however, and the authors state that even in the most favorable cases the yields were extremely poor. The next report on the preparation of this compound appeared in the literature when Schiemann (10) announced that nitration of o-fluorotoluene gave 2-nitro-6-fluoro- - 2 toluene and 5-nitro-6-fluorotoluene in yields of 14 and 72 per cent, respectively. Lock (11), in 1936, reported the preparation of 2nitro-6-fluorotoluene from 2-nitro-6-aJJJ.inotoluene using the method developed by Schiemann (13) for the replacement of an amino group in an aromatic nucleus by fluorine. This method consists in the diazotization of the amine followed by treatment of the diazo salt with fluoboric acid or sodium fluoborate, which causes the insoluble diazonium fluoborate to precipitate. The dried diazonium fluoborate is then thermally decomposed liberating nitrogen and boron trifluoride; leaving the nitroaryl fluoride which may then be distilled off. The reactions may be represented as follows: d CH OzN NH2 + HBF 4 ~ The yields obtained in these reactions are 80% of the theory of the diazonium fluoborate and a 63% yield of the aryl nitrofluoride calculated from the diazonium fluoborate, which - 3 - gives approximately a 50% over-all yield of the nitrofluorotoluene. While this yield is perhaps none too high, it is reasonably satisfactory, and apparently the best method yet devised for the preparation of the desired compound. There- fore it was chosen as the method to be used in this investigation subsequent to the preparation of 2-nitro-6-aminotoluene. 2,6-Dinitrotoluene has been prepared by several methods since it was first obtained as a nitration product of toluene by Cunerth (12), but the yields from the various syntheses were low. The method of Holleman and Boeseken (13) which consisted of selective reduction of 2,4,6-trinitrotoluene by ac"1lllloniuin sulfide to 2,6-dinitro-4-aminotoluene, which was then deaminated by reduction of the diazo salt of the amine by ethanol, was one of the best methods reported though their over-all yield of dinitrotoluene was low. Consequently a new method for the preparation of 2,6-dinitrotoluene was sought. A logical approach to the problem seemed to be via the hydrolysis of 2,6-dinitro-p-toluenesulfonic acid which is readily obtained from toluene by suJ.fonation followed by nitration (14). To this end a quantity of 2,6-dinitro-p- toluenesulfonic acid was prepared, but all attempts to hydrolyze it to 2,6-dinitrotoluene met with failure. The usual methods for the hydrolysis of sulfonic acids of steam and superheated steam distillations, refluxing with dilute - 4 and strong mineral acids were all applied, but resulted in the formation of negligible amounts of the desired dinitrotoluene. Consequently this method was abandoned and the known syntheses were studied in the hopes of ameliorating the yields obtained by earlier investigators. - 5 - 2,6-Dinitro m- and p-Toluenesulfonic Acids To 184 g. of concentrated sulfuric acid, 100 g. of toluene were added dropwise. T'.ae reaction mixture was allowed to cool to room temperature, and 500 g. of fuming nitric acid (sp. g. 1.50) were slowly added with frequent agitation of the reaction vessel. The reaction mixture was then reflu:ced for 4 hours under the hood. Excess ni trio acid was distilled off, and upon cooling a mixture of isomeric dinitrotoluenesulfonic acids crystallized. This mixture consists principally of the p-isomer with a small amount of them-isomer present (14). Hydrolysis of the dinitrotoluenesulfonic acids was attempted by refluxing aqueous solutions for long :periods of time, but no 2,6-dinitrotoluene was formed. In other experiments, hydrolysis of the sulfonic acids was attempted in sulfuric and nitric acid solutions of various concentrations, but these efforts were also unsuccessful from a preparative viewpoint. Steam and superheated steam . distillations at 180° likewise gave no appreciable yields of the desired dinitrotoluene. - 6 2,41..6-Trinitrotoluene To a mixture of 200 g. concentrated nitric acid and 800 g. concentrated sulfuric acid contained in a 3-necked liter flask equipped with a stirrer, were added, in small portions, 100 g. of p-nitrotoluene. The reaction mixture was continuously stirred while the temperature was slowly raised to 120° over a period of five hours. Tne reaction mixture was allowed to cool to about 90°, and was then poured into ice water. Tne trinitrotoluene was filtered, washed well with water, and recrystallized from 907h ethanol. The yield obtained was 145 g. (about 82% of the theoretical value) of 2,4,6trinitrotoluene, m.p. 81°-82°. - ? - 2,6-Dinitro-4-Aminotoluene To 100 g. of 2,4,6-trinitrotoluene suspended in 500 ml. of ethanol are added 2.5 ml. of concentrated ararnonium hydroxide. The solution is cooled in an ice bath, and hydrogen sulfide gas is passed into the reaction mixture until all of the trinitrotoluene has reacted. As the reduction proceeds, the flask is filled 'With a flocculent, yellowish precipitate, and the reaction is complete when all of the heavy trinitrotoluene crystals, which settle to the bottom of the flask, have disappeared. The reaction mixture is heated on the steam funnel, and then filtered. The sulfur precipitate is washed 'With hot ethanol until the filtrate runs through colorless. The alcoholic filtrate is poured into an ex- cess of water, whereupon the insoluble hydroxylam:i.ne is precipitated. After allovang to stand for a few minutes, the precipitate is collected and heated with potassium iodide and concentrated hydrochloric acid. • Heating is continued until the reaction mixture ceases to liberate free iodine vapors. Water is added to the crude dinitro- aroine; the product is filtered, and washed well 'With water. ine residue is extracted with hot dilute hydro- chloric acid until a test portion of the extract no longer gives a precipitate of the amine upon neutralization. The combined extracts are neutralized with - 8 - ammonium hydroxide, and the precipitated 2,6-dinitro4-aminotoluene is collected. The yield is 47.5 g. (55%). The product is purified by recrystallization from 40% acetic acid, or from 60% ethanol. - 9 2,6-Dinitrotoluene A. Ethanol Deamination of 2,6-Dinitro-4-Am.:i.notoluene. 1. Diazotization in H2so 4 with ~itrosylsulfuric Acid. Four grams of 2,6-dinitro-4-aminotoluene are dissolved in 30 ml. concentrated n2so 4 . The solution is cooled to o0 in an ice bath and 2.2 g. NaN0 2 dissolved in 10 ml. concentrated R. 2so 4 are slowly added with continuous rapid stirring of the reaction mixture. After the diazotization is complete, the reac- tion mixture is poured into 200 ml. of boiling ethanol and refluxed for 15 minutes. The alcoholic solution is then poured into about 4 times its volume of water, and the residue which separates upon cooling is filtered off and steam distilled. Tne yield of 2,6-di- ni trotoluene is O. 7 g. ; about 25% of the theory. The compound is purified by recrystallization from low boiling petroleum ether. 2. M.P. - 61°-62°. Diazotization in 1:1N0 3 with Sodium Metabisulfi te. To 50 ml. fuming nitric acid (sp. g. 1.49) is added in small portions, with vigorous stirring, a mixture of 9.8 g. 2,6-dinitro-4-aminotoluene and 5.9 g. sodium metabisulfite. After the last portion has been added, the react.ion is allowed to continue until a test drop of the reaction :mixture placed in a little water gives a clear solution. The reaction mixture is ·jjhen poured into 300 ml. boiling ethanol and refluxed for - 10 10 minutes. One liter of water is added, and the reaction mixture is cooled to o0 • Upon cooling, 2,6- dinitrotoluene crystallizes, and is filtered from the solution. It is purified by steam distillation, and recrystallization from petroleum ether. The yield is 4.4 g.; about 487& of the theoretical. B. Hypophosphorus Acid Deamination of 2,6-Dinitro-4-AminoToluene. In 50 ml. glacial acetic acid are dissolved 1.97 g. (0.01 mole) of 2,6-dinitro-4-aminotoluene. The solution is cooled to o0 , and 45 ml. of concentrated HCl are added. To this mixture 2.1 g. (0.03 mole) NaN0 2 are slowly added vdth rapid stirring, maintaining the temperature of the reaction mixture at 0°-5°. The reaction is allowed to continue for 10 minutes after all the nitrite has been added, and then 5.2 ml. of 50~,~ H3Po 2 (0.05 mole) are added dropwise. After all the h3P0 2 has been added, stirring is continued for one hour, and the reaction mixture, loosely stoppered, is then stored in the refrigerator at approximately o0 • The reaction takes about 24 hours to reach completion, and the 2,6-dinitro-4-ami.notoluene is recovered from the reaction product by steam distillation. It is purified by recrystaJ.lization from petroleum ether. T"ne yield is O. 95 g. -- 5250 of the theory. The percentage yields obtained using other proportions of NaN0 2 and H3P0 2 ·with HCl and H2s0 4 as the solvents for - 11 - the amine are shovm. in Table I below. Table I Deamination-9.1_..&.i..§-Dinitro-4-Aminotoluene Solvent Moles of Amine lvloles of NaN0 2 Moles of H3Po 2 Yield of Dini trotoluene h 2SO 4 0.01 0.01 0.10 279; H2so 4 0.01 0.01 0.05 24% HCl 0.01 0.01 0.05 3810 HCl 0.01 0.01 , 0.10 40'I1~ HCl 0.01 0.05 0.05 39% HCl 0.01 0.04 0.05 50% HCl 0.01 0.03 0.05 52% HCl 0.01 0.02 0.05 467; f - 12 - 2-Nitro-6-Juninotoluene To 25 g . of 2,6-dinitrotoluene are added 100 ml. of ethanol and the mixture is brought to boiling on the steam funnel. Then 140 ml. of 151& ammoniu..m sulfide are gra dually introduced with frequent agitation of the reaction flask. The solution is refluxed for 15 minutes after all the ammonium sulfide has been added. Most of the alcohol is then removed, and the residue is repeatedly extracted with hot dilute .ttCl. The combined extracts are neutralized w:i. th NH40H, cooled, and the precipitated aJJri.ne collected. amine is purified by recrystallization from water. yield is 16.6 g. (80% of the theory), m.p. 90°- 91°. The The - 13 2-Fluoro-6-Nitrotoluene To 20 ml. concentrated HCl are added 13 g. 2-nitroThe solution is cooled in an ice bath, 6-arninotoluene. end 8.55 g. NaN02 in concentrated aqueous solution are slowly added with continuous stirring. After the diazo- tization is complete, the solution is filtered rapidly into a cold flask, and 13.0 g. of NaBF 4 in concentrated aqueous solution (precooled to o0 ) are added. A white, curdy precipitate of the diazonium fluoborate is formed immediately. After allowing to stand for a few minutes, the solution is filtered and the diazonium fluoborate collected. The precipitate is washed with concentrated NaBF 4 solution, then ·with methanol, and finally with cold water. The product is dried in vacuo over P 205. The yiel9- is " 20 g. Ten grams of the diazonium fluoborate are placed in a 50 ml. distilling flask to which is attached a small Liebig condenser. The receiver is connected to a series of three gas washing bottles contai~ing dilute aqueous NaOH to absorb the boron trifluoride liberated in the decomposition. The system is evacuated to about 30 rum. pressure, and the reaction flask heated cautiously with a small free flame. AB soon as the decomposition starts, the flame is removed and not reapplied until the reaction moderates. When all the diazonium. fluoborate has decomposed, - 14 - the reaction flask is heated more strongly until all the 2-nitro-6-fluorotoluene has distilled over. The product is taken up with ethyl ether, and washed with dilute aqueous Na0H. The ethereal solution is dried with Cac1 2 . The ether is distilled off, and the 2-nitro-6-fluorotoluene is redistilled. '11he yield is 3.5 g. (60o/; calculated from the diazonium fluoborate); b.p. - 205°. Analysis: C H N Cale. 54.20 3.90 9.04 li'ound 54.43 3.98 9.22 - 15 Discussion The influence upon the ease of hydrolysis of various substituents in the nucleus of aryl sulfonic acids is difficult to predict with certainty, but Armstrong and rn.iller (15) have shown that, in general, the presence of methyl ortho or para to the sulfonic acid group facilitates hydrolysis. Bromine appears to retard the reaction, and many di, tri, and tetrabromobenzenesulfonic acids hydrolyze only when treated with concentrated hydrochloric or hydrobromic acids at temperatures ranging from 150° to 250° {16,17 ,18,.19). 3,5-Dinitro-4-bromobenzenesulfonic acid is wichanged by refluxing with 60% H2so 4 or by heating with 20% H2so 4 at 170° {20). If, in this molecule, the bromine is replaced by methyl, we obtain 2,6-dinitro-p-toluenesulfonic acid which compowid should be more easily hydrolyzed than the bromosulfonic acid if a methyl group para to the sulfonic acid group increases the ease of hydrolysis. Nevertheless, it has been shown in this investigation that the 2,6-dinitro-~-toluenesulfonic acid is very difficult to hydrolyze. It is inter es ting to note that the fully substituted sulfonic acid, 3,5-dinitro-2,4,6-tribromobenzenesulfonic acid is hydrolyzed by heating in aqueous solution at 230° . {19). Very little work on the hydrolysis of aromatic nitrosulfonic acids appears in the literature. Vesely and Stojanova (21) have reported on the hydrolysis of variously substituted aryl sulfonic acids by concentrated phosphoric acid. - 16 - They were unable to decompose nitrobenzenesulfonic acid by the use of phosphoric acid even at temperatures above 200°. It thus appears, from. what little evidence that is available, that the nitro group exerts an inhibiting effect upon the hydrolysis of aryl sulfonic acids. In addition to the procedure already described, toluene was nitrated to 2,4,6-trinitrotoluene using higher temperatures and shorter periods of nitration. These nitrations, however, were not nearly as effective as the other method. For example, nitration at 120°-125° for a period of 2½ hours gave only a 7111' yield of' trinitrotoluene. .l:!'urthermore, if the temperature of the reactants is raised too rapidly, when approximately 120° is reached, the violence of the reaction causes so much heat to be developed that external cooling must be applied to bring the temperature of the reaction mixture down ¥Ii thin the bounds of safety. Considerable difficulty was at first experienced in the reduction of 2,4,6-trinitrotoluene to 2,6-dinitro-4-aminotoluene in appreciable yields. The early work on the syn- thesis of this compound by Tiemann ( 21), Beilstein ( 22), and Holleman and Boeseken (13) consisted in the selective reduction of the trinitrotoluene to the dinitroarnine by the use of ammonium sulfide. The work of Holleman and Boeseken who reported yields of the order of 20% of the theoretical value was repeated with essentially the same results as they obtained. The reaction product was - 17 - difficult to work i.ti th, and the crude amine had to be repeatedly recrystallized before attaining a sufficiently high degree of purity. Cohen and co-workers (23,24) were the first to report good success in the reduction of various polynitro aromatic compounds using hydrogen sulfide and only a trace of ammonia. Tne ammonia ostensibly merely catalyzes the reaction inasmuch as it may be replaced by other bases such as primary, secondary, and tertiary alifatic amines, benzylamine, or piperidine. The weak bases, aniline, pyridine, and phenylhydrazine, however, are not suitable for effecting the reduction. Such a reduction results, in the case of 2,4,6-trinitrotoluene, in a mixture of 2,6-dinitro-4-aruinotoluene and 2,6-dinitro-4hydroxylaminotoluene. heating with concentrated hydrochloric acid and potassium iodide reduces the hydrox-_ylaruine to the amine. This method is preferable to reduction by ammonium sulfide in many cases. In addition to the large amounts of gummy polysulfides formed when much ammonia is used, which make it difficult to work up the reaction product, Cohen and ivicCandlish have shovm that some hydroxylamines are very sensitive to the action of ammonia, forming in some cases new crystalline compounds, in others tarry products. In both cases the diminished yield of amine v~1ich is frequently experienced when much ammonia is used may be thus explained. A considerable portion of the work of the investigation consisted in the study of the deamination of 2,6-d.initro-4- - 18 - aminotoluene. Although Holleman and Boeseken (13) reported the deamination of 2, 6-dini tro-4-am:i.notoluene in "almost theoretical yield" to 2,6-dinitrotoluene by diazotization of the amine in sulfuric acid with sodiwu nitrite, followed by reduction of the diazo salt vd th ethanol, numerous attempts to repeat their work gave at best only a few per cent yield of the dinitrotoluene. They carried out the diazo- tization using equal quantities of concentrated sulfuric acid a.n.d water as the solvent for the amine, and aqueous sodium nitrite. Bince this method proved ineffective, mod- ifications of the procedure were adopted using higher concentrations of sulfuric acid and nitrosylsulfuric acid as well as aqueous sodium nitrite for the diazotization. l\Jone of these modifications, however, produced a yield of 2, 6dini trotoluene of more than about 25% of the theoretical, which yield was obtained when concentrated sulfuric acid was used for the solvent, and nitrosylsulfuric acid was used for the diazotization. Diazotization of the amine using the method of Witt (25) gave considerably better results. The principle of this method is to use concen- trated nitric acid as the solvent for the amine, and at the same time derive from it the nitrous acid necessary for diazotization by the action of a suitable reducing agent such as sodium metabisulfite. This method gave a more nearly complete diazotization than could be achieved in sulfuric acid. The amine may also be diazotized by dis- solving it first in glacial acetic acid, then adding - 19 - concentrated hydrochloric acid and sodium nitrite. Dea.mi.nation of the diazotized amine ~~th hypophosphorus acid was found to give somewhat better results than ethanol deamination. The reduction of a diazotized amine by hypophosphorus acid (27) may be represented by the folJ.o·wing equation: t- ArN2X - + H3P0 2 + H20 According to the equation, one mole of hypophosphorus acid. ·will be required per diazo group, but in laboratory practice an excess of five to ten, or in some cases even more, moles of hypophosphorus acid per mole of diazonium compound is usually necessary to achieve the best results. This is not invariably true, however, and in the case of 3-nitro-4-a.minotoluene as little as 0.76 mole gives a 70% yield of m-nitrotoluene (26). The proper ai.~ount to be used with an individual amine must be deterrnined by experiment. In the case of 2,6-dinitro-4-am.inotoluene, 5 moles of hypophosphorus acid per mole of diazotized amine was found to be the correct proportion to use for the deB.L71.ination. It was also determined that a proportion of 3 moles of sodium nitrite per mole of amine gave maximum yields. Deamination of the diazotized amine using the stabilized di~zonium salt method of liodgson and Marsden ( 28) was also investigated. In this method, an aqueous solu- tion of the diazotized runine is treated with the molar quantity of naphthalene-1, 5-disulfonic acid or with - 20 - 2-naphthol-1-sulfonic acid vvhich causes the insoluble diazoniuru salt to precipitate. Tne dry salt is then reduced at room temperature in ethanol containing zinc or copper. The method was found to be unsuitable for the deamination of 2,6-dinitro-4-aminotoluene. Of the reducing agents in- vestigated, hypophosphorus acid gave the best results. 2-Ni tro-6-aminotoluene has usually been prepared by ammonium sulfide reduction of 2,6-dinitrotoluene in the cold or at room temperatures (12,29). This procedure usually results in fair yields of the product, but the reaction mixture is invariably contaminated with tarry poly.sulfides and is difficult to purify. It was discovered that if the reaction is carried out at the temperature of boiling ethanol, the yields are somewhat higher, and the product is more easily purified. - 21 - Summ.ar_y 2f Thesis 1. The following compounds were synthesized: 2,6- dini tro-p-toluenesulfonic acid, 2,4,6-trinitrotoluene, 2,6-dinitro-4-aminotoluene, 2,6-dinitrotoluene, 2-nitro6-runinotoluene, and 2-nitro-6-fluorotoluene. 2, 2,6-Dinitro-p-toluenesulfonic acid could not be hydrolyzed in yields greater than a few per cent by application of the ordinary methods for the hydrolysis of aryl sulfoni c acids. 3. The optimum experimental conditions for the de- amination of 2,6-dinitro-4-arninotoluene by hypophosphorus acid iNere determined. 4. An improved method. for reducing 2, 6-dini trotoluene to 2-nitro-6-aminotoluene was devised. - 22 - References 1. o. ·wall a ch, .@ll• , ~ ' 260, ( 1886) . 2. G. Schiemann and W. Roselius,~-,.§.§., 1439, (1932). 3. G. Schi emann and W. Wink:elmuller, J. Prakt. Chem., 135, 101, {1932). 4. G. Schiemann, l_. Prakt. ~ - , Jd.Q_, 97, (1934). 5. c. Niemann, A. Benson, and J. lVlead, J ._!.C.§_., 63, 2204, (1941). 6. c. Niemann and Ivi. Rapport, J-.!.C.§.., £.'2., 1671, (1946). 7. J- . English, J. Mead, and C. Niemann, J- .A.C.S., .§.g, 3 5 0 , ( 19 40 ) . s. c. Niemann, J. l1Iead, and A. Benson, J .A.Q..S., 63, 609, (1941). 9. J-. van Loon and V. Meyer, ~ - , ~ ' 841, (1896). 10. G. Schiemann, oer., 62, 1797, (1929). 11. G. Lock:,~-, .§2, 2257, (1936). 12. o. Cunerth, .Ann., 172, 222, (1874). :}.3. A. Holleman and J. Boes elcen, ~ - ~ Trav. Chim. de Pays~' 16, 425, (1897). 14. W. Marck:wald, Ann., 274,349, (1893). 15. H. Arm.strong and A. Miller, J-. ~ - §.Q_Q_., 41L_ 148, (1884). 16. H. Lim:pricht, Ber., 10, 1539, (1887). 17. A. Langfurth, Ann., 191, 188, {1878). 18l o. Reinke, Ann., -l,8.-2,, 272, (1877). 19. R. Bassmann, Ann., 191, 206, {1878). - - - 23 20. F. Ulmann and E. Kuhn, :Anll·, ~ ' 103, {1909). 21. V. Vesely and T. Stojanova, .f.211. Czech. Chem. Commun., 2,465, {1937). C.A., 32, 1549, (1938). 22. F. Tiemann, ~ . , 3, 218, (1870); 23. J:i' . Beilstein, Ber., 13, 243, 24. J. Cohen and H. Dakin, J. ~ - So_.£., 81, 27, ( 1902). 25. J. Cohen and D. McCandlish, J. Chem. Soc., 87, 1257, (1880). (1905). 26. R. Manske, L. :Marion, and :b' . Leger,.£@;. J. Research, 20 B, 133, (1942). 27 • J • iv1ai , ~ . , 3 5 , 16 2 , ( 19 0 2 ) . 28. J:i. Hodgson and E. Marsden, 29. H. viJheeler, Am. ~ - J., 44, 136, (1910). J. Chem. Soc., 207, (1940).