Toluene from o-toluidine

Toluene. from-o-Toluidine. In a 1-L flask are placed 21.4 g. (0.2 mole) of o-toluidine, 76 cc. of concentrated hydrochloric acid (sp. gr. 1 19), and 26 cc. of water. The flask is immersed in an ice-salt mixture and is fitted with an effident stirrer. While a temperature of —6° to 0° is maihtained, a solution of 14.6 g. (0.204 mole) of 97% sodium nitrite in 36 cc. of water is slowly added from a dropping fvmnel. As the reac- tion proceeds, the mixture becomes more fluid and the nitrite may be added somewhat more rapidly one-half to three-quarters of an hour is required for diazotization. 

Tolunitrile has also been prepared from o-toluidine by conversion into o-tolyl isothiocyanate and the boiling of this under a reflux condenser 4 />-tolunitrile has been prepared by distilling />-toluic acid with potassium thiocyanate 5 and a mixture of the two has been produced by the interaction of toluene, mercury fulminate, and aluminium chloride.6... 

The removal of the nitrogen atom from o-toluidine proceeds via two reactions by direct C-N bond cleavage of toluidine to toluene and ammonia (path 1), and by hydrogenation of o-toluidine to methylcyclohexylamine (path 2), which reacts further to methylcyclohexene, methylcyclohexane and ammonia [2]. Fig. 2 shows the influence of the initial partial pressure of o-toluidine on the selectivity for the products of these two pathways. Varying the initial partial pressure of o-toluidine in the reactant mixture did not affect the product selectivity. This indicates that either both reactions occur on the same site with the same order of reaction, or that o-toluidine has the same adsorption constant on the sites for path 1 and path 2. 

The method of preparation adopted is substantially that of Buchka,- as this is the only one of practical value. w-Nitro-toluene has been obtained by a similar process from 5-nitro-2-aminotoluene (obtained by nitration of acetyl-o-toluidine), but this compound is not commercially available, and gives a poor product unless carefully purified. 

Diaminotoluene has been prepared from 2,4-dinitro-toluene by reduction with iron and acetic acid,2 and by electrolytic reduction 3 from 4-nitro-o-toluidine by reduction with tin and hydrochloric acid 4 and from 2,4-dinitrobenzoyl chloride with tin and hydrochloric acid. ... 

Haussermann 2 reduced nitrobenzene and nitrotoluenes both in alkaline and acid solution, the former with iron, the latter with platinum, electrodes. By reduction in alkaline solution, he obtained as principal product hydrazobenzene and hydrazo-toluene respectively in sulphuric-acid solution he got from nitrobenzene, as chief products, benzidine sulphate and azoxy-benzene, besides an easily changeable body which was not further determined. o-Nitrotoluene3 under like conditions gave o-tolui-dine sulphate besides small quantities of o-toluidine p-nitro-toluene yielded principally p-toluidine. 

While the direct halogenation of toluene gives a mixture of isomers that is difficult to separate into the pure isomers, the isomeric o- and /r-nitrotoluenes 6a and 6b, formed by nitration, are easy to separate from each other. Thus reduction of the single o- or /j-nitrotoluene 6 to the o- or /j-toluidine 7a or 7b respectively, followed by conversion into the corresponding diazonium salt 8 and a subsequent Sandmeyer reaction leads to the pure o- or /j-halotoluene 9. 

Similarly, benzene and hydrazoic acid in the presence of a mixture of fluorosulphonic and trifluoromethanesulphonic acid give aniline quantitatively. From toluene 100% of a mixture of o-, m- and p-toluidines is obtained and bromobenzene yields 42% o-bromoaniline and 47% p-bromoaniline, Butyl azide gives iV-butylarylamines under these conditions89. Photolysis of 1-aminoquinolinium perchlorate (76) in aromatic hydrocarbons (benzene, toluene, ethylbenzene or mesitylene) in the presence of 18-crown-6 affords arylamines, e.g. aniline and p-toluidine, by way of the nitrenium ion90 cf Reference 91. 

A study using a model reaction system consisting of cumene hydroperoxide (CHP), A,A-dimethyl-/)-toluidine (DMPT), and o-benzoic sulfimide (saccharin) in toluene (without reactive acrylic monomer) showed conclusively that the DMPT was depleted significantly during the initiation step of an anaerobic reaction. The saccharin concentration was unchanged during this process. The initiating species may be radical anions derived from DMPT rather than reactive free radicals derived from the CHP [17]. 

Scheme 10.14. The formation of aminobenzene (aniline) and o- and p-methylaminobenzenes (o- and p-toluidines) from the nitration of a mixture of benzene and methylbenzene (toluene) and subsequent reduction of the mixture with iron (Fe) in acetic acid (CH3CO2H).

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