Aliphatic amines, reactions with nitrous

Primary aliphatic amines react with nitrous acid through a reaction called diawtization to yield highly unstable aliphatic diazonium salts. Even at low temperatures, aliphatic diazonium salts decompose spontaneously by losing nitrogen to form carbocations. The carbocations go on to produce mixtures of alkenes, alcohols, and alkyl halides by removal of a proton, reaction with H2O, and reaction with X ... 

Aromatic primary amines differ markedly from aliphatic amines in their reaction with nitrous acid. Thus a cold aqueous solution of mono thylamine hydrochloride reacts with nitrous acid to give mainly the corresponding primary alcohol ... 

Primary aromatic amines differ from primary aliphatic amines in their reaction with nitrous acid. Whereas the latter yield the corresponding alcohols (RNHj — ROH) without formation of intermediate products see Section 111,123, test (i), primary aromatic amines 3neld diazonium salts. Thus aniline gives phcnyldiazonium chloride (sometimes termed benzene-diazonium chloride) CjHbNj- +C1 the exact mode of formation is not known, but a possible route is through the phenjdnitrosoammonium ion tlius ... 

Recently [35a] it has been found that, contrary to common belief, tertiary aliphatic amines react with aqueous nitrous acid to undergo dealkylation to form a carbonyl compound, a secondary nitrosoamine, and nitrous oxide. Base-weakening groups markedly reduce nitrosative cleavage, and quaterniza-tion prevents it completely. Several examples of this reaction are shown in Table II. 

Primary aromatic amines on reaction with nitrous acid in the presence of hydrochloric acid (or other mineral acid) at about 0 °C yield diazonium salts as discrete intermediates. The diazonium salts similarly derived from aliphatic primary amines decompose readily even at this temperature to yield the corresponding alcohol (and other products) with the evolution of nitrogen. 

Methylation and acetylation provide confirmatory evidence for the assignment of various bands to aliphatic components in the humic substances (Wagner and Stevenson, 1965 Flaig et al., 1975 Stevenson, 1982). The presence of amine groups in a peat fulvic acid has been confirmed by observing the changes in the infrared spectra of the sample following reaction with nitrous acid (MacCarthy and O Cinneide, 1974). 

In water, tertiary amines form quaternary ammonium compounds, e. g. with methyl halogenides. In aqueous solution, secondary (aliphatic and aromatic) amines react with nitrous acid HONO (namely the nitrosonium ion NO ) as already mentioned (reaction 5.217) to generate nitrosamines ... 

Primary aromatic amines react with nitrous acid to form arenediazonium salts, which, unlike their aliphatic counterparts, are stable at 0°C and can be kept in solution for short periods without decomposition. When an arenediazonium salt is treated with an appropriate reagent, nitrogen is lost and replaced with another atom or functional group. What makes reactions of primary aromatic amines with nitrous acid so valuable is the fact that the — NH2 group can be replaced with the groups shown. 

Reactions in which a bond from carbon to nitrogen is broken are important in several areas of organic chemistry. The Hofmann and Cope eliminations are widely used in synthetic chemistry, and the deamination of aliphatic amines (via the nitrous acid, nitrosoamide and triazene methods) has been widely studied, usually with a primary emphasis on establishing the mechanism of the reaction. Since there has been much research activity in the latter area recently, a major fraction of the chapter is devoted to an interpretive and critical review of the deamination reactions. 

When primary aromatic amines are treated with nitrous acid, diazonium salts are formed. The reaction also occurs with aliphatic primary amines, but aliphatic diazonium ions are extremely unstable, even in solution (see p. 448). Aromatic diazonium ions are more stable, because of the resonance interaction between the nitrogens and the ring ... 

For aromatic amines, the reaction is very general. Halogen, nitro, alkyl, aldehyde, sulfonic acid, and so on, groups do not interfere. Since aliphatic amines do not react with nitrous acid below a pH of 3, it is even possible, by working at a pH of 1, to diazotize an aromatic amine without disturbing an aliphatic amino group in the same molecule. ... 

Write the reactions of (I) aromatic and (II) aliphatic primary amines with nitrous aeid. 

The best known example of the treatment of a primary aliphatic amine with nitrous acid involves the reaction of esters of glycine hydrochloride with sodium nitrite to form esters of diazoacetic acid. This reaction is carried out at low temperatures and under such reaction conditions that any IV-nitroso primary amine which might have been formed is immediately converted to the diazoacetate [15, 16]. Treatment of 1-methyl-2,2,2-trifluoroethylamine hydrochloride, another primary amine, with sodium nitrite in an aqueous system also evidently leads to the corresponding diazoalkane [17]. 

The treatment of aliphatic amines with nitrous acid is not a useful method for the preparation of olefins any more than it is for the preparation of alcohols (p. 355), though some olefin is usually formed in such reactions. 

The spontaneous decomposition of the diazonium ions obtained on treating non-aromatic primary amines with nitrous acid in weakly acidic solutions (deamination reaction) is an irreversible reaction possessing great driving force under mild conditions. The steric consequences of the reaction in the aliphatic and alicyclic fields have proved to be quite diverse, "... 

With nitrous acid. The reaction of the aromatic primary amines with nitrous acid is different from that of the aliphatic primary amines with the same reagent, and serves to distinguish the two groups of compounds. When a primary alkyl amine is treated with nitrous acid the hydroxyl compound of the radical is formed and all of the nitrogen of the amine is given off as free nitrogen. The reaction is as follows ... 

Primary aliphatic amines also react with nitrous acid to yield diazonium salts but since aliphatic diazonium salts are quite unstable and break down to yield a complicated mixture of organic products (see Problem 23.11, below), this reaction is of little synthetic value. The fact that nitrogen is evolved quantitatively is of some... 

Tertiary aliphatic amines (and, to an extent, tertiary aromatic amines, too, particularly if the para position is blocked) react with nitrous acid to yield an N-nitroso derivative of a secondary amine the group that is lost from nitrogen appears as an aldehyde or ketone. Although this reaction is not really understood, it too seems to involve the initial attack by NO on nitrogen. 

Problem 36.15 The reaction of primary aliphatic amines with nitrous acid gives a quantitative yield of nitrogen gas, and is the basis of the Van Slyke determination of amino nitrogen. What volume of nitrogen gas at S.T.P. would be liberated from 0.001 mole of (a) leucine, (b) lysine, (c) proline — ... 

Treatment of a primary aliphatic amine with nitrous acid or its equivalent produces a diazonium Ion which results in the formation of a variety of products through solvent displacement, elimination and solvolysis with 1,2-shift and concurrent elimination of nitrogen. The stereochemistry of the deamination-substitution reaction of various secondary amines was investigated as early as 1950, when an Swl-type displacement was suggested. Thus, the process can hardly be utilized for the preparation of alcohols except in cases where additional factors controlling the reaction course exist. Deamination-substitution of a-amino acids can be utilized for the preparation of chiral alcohols. 

Again it should be emphasized that this mechanism represents an oversimplification of the actual course of the reaction of nitrous acid with aliphatic amines (see p. 40). Htickel and Wilip24 have found, for example, that in aqueous solution Z-menthylamine (XXXIX) is transformed with no inversion or racemization into Z-menthol (XL). When the reaction is carried out in aqueous alcohol, however, the ether which is formed is partially racemized (XLI and XLII). The formation of a... 

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