Methylaniline, nitrosation

Butyl-3,3-di-n-butylpseudourea, 174 2-n-Buty 1-3,3-diisopropylpseudourea, 178 2-n-Buty 1-1,3-di-p-tolylpseudourea, 170 Butylidenepropylamine, 256 TV-r-Butyl-yV-methylaniline, nitrosation of,... 

There is no reference to the formation of the ortho nitroso amine in the benzene series, indeed the formation and characterisation of ortho nitroso amines from any reaction has only been reported once or twice79. When the para position is blocked by a substituent, de-nitrosation so the secondary amine can occur80 a certain amount (which depends on the conditions) of denitrosation occurs also, concurrently with the rearrangement81, so that N-nitroso-N-methylaniline (XLVII) yields N-methylaniline (XLVIII) as well as the rearrangement product p-nitroso-N-methylaniline XLIX, viz. 

It is claimed that the limiting value of k bs, 2.81 x 10" sec-1, represents the rate coefficient for the rearrangement reaction above (k,). The ring deuterium isotope effect kH kD was re-determined for this individual rate coefficient for rearrangement by finding the limiting value in the presence of added N-methylaniline and was found to be 2.4 at two different acidities, as compared with 1.7 for the ratio of the observed composite rate coefficients, as expected, since no isotope effect would be predicted for the de-nitrosation step. 

Nitrosocarbazole condenses with 9-aminocarbazole to give the azo compound 122, heating of which produces dimers in a ratio similar to that observed by oxidation of carbazole (see Section II,A,2) it was therefore believed to involve the carbazol-9-yl radical. 3-Nitro-9-nitrosocarbazole was shown to serve as a nitrosating agent for A-methylaniline it converted aziridine to ethene and nitrous oxide. ... 

As indicated above, tertiary aromatic amines are directly C-nitrosated. The usual reagents are sodium nitrite and dilute hydrochloric acid, sodium nitrite and glacial acetic acid containing concentrated hydrochloric acid, and nitrite esters with hydrochloric acid [21a, 27]. While tertiary amines with such complex alkyl groups as found in A,A-di(3,5,5-trimethylhexyl)aniline are readily nitrosated [25], of the four A-butyl-A-methylaniline isomers, JV-r-butyl-A-methylaniline does not undergo the reaction, and even the nitroso compounds which did form were only unstable oils [27]. 

N-nitrosation and simultaneous C-nitration of secondary aromatic amines by aqueous solution of N204 has been studied by Stoermer [61] and Ruff and Stein [62], Thus N-methylaniline yielded N-methyl-n-nitroso-p-nitroaniline. 

It appears that the NO+ group can be transferred directly only to those species which can behave as reasonably powerful nucleophiles in moderately acid solution. This is undoubtedly the reason why species such as azide ion and amines do not appear to act in this way since they are very extensively protonated in these solutions. Azide ion catalysis has been reported in one case, however (Meyer and Williams, to be published) the denitrosation of N-acetyl-N-nitrosotryptophan, which reacts very rapidly, has been examined at pH 6 where a substantial quantity of free azide ion exists. Presumably the same would be true for some amines at these very low acidities. However, there is experimental evidence from two independent groups which shows that a direct (sometimes called trans-) nitrosation by nitrosamines can occur with aromatic amines. The reactions of N-nitrosodiphenylamine in aqueous acid solution were studied in this context (Challis and Osborne, 1973). The reaction was acid-catalysed for all the substrates studied and was believed to involve the protonated form of the nitrosamine (here written as PhjNNO, H" ). Two separate pathways were detected (a) a direct reaction with N-methylaniline (without the formation of free nitrous acid or a derivative of nitrous acid) as outlined in Scheme 20 and b) an indirect reaction with... 

Diazotization. In almost all its reactions, nitrous acid attacks a point of high electron density. The nitrosation of methylaniline and dimethylaniline are examples ... 

Scheme 10.41. The Fiscfaer-Hepp rearrangement. A representation of nitrosation (with either nitrous acid [HONO] or nitrosyl chloride [NOCl]) vide suproy this chapter) of A-methylaminobenzene (A-methylaniJine) produces the corresponding Af-nitroso derivative and the latter, on treatment with hydrogen chloride, undergoes intramolecular rearrangement through attack by A-methylaminobenzene (Af-methylaniline). 4-Nitroso-Af-methylaminobenzene (4-nitroso-A-methylaniline) results. For the Fischer-Hepp process here and in the next scheme see Fischer, O. Hepp, E. Chem. Ber., 1886, 19, 2991 and Johal, S. S. Williams, D. L. H. Buncel, E. J. Chem. Soc. Perkin Trans. II, 1980, 165.

The details of this new mechanism have been examined only recently. It is certain that the initial A-nitrosation is again rate determining, because equation (56) is also observed in nitrosamine formation from iV-methylaniline under similar experimental conditions . Equations (55) and (56) differ only in their dependence on the amine moiety the nitrosating reagent is probably the same positively charged species in both cases, but for equation (55) the rate-determining process is attack on the free amine, for equation (56) on the... 

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