Nitric esters hydrolysis

What has been said about sulfonic esters applies also to sulfuric, phosphoric and nitric esters and of course the hydrolysis of halides must necessarily always yield a carbonium cation. 

The reactivity of nitric acid esters and in particular the complicated chemical composition of the products formed by their hydrolysis led some investigators [1, 37] to express the view that nitric esters may have the structure of peroxy-compounds (I) ... 

However, the alcohol and acid formed during the hydrolysis of nitric esters are accompanied by a range of other compounds such as aldehydes, ketones, hydroxy-carboxylic acids, unsaturated hydrocarbons, nitrous add, etc. (e.g. reference [107]). 

Much experimental work has been carried out in seeking an explanation of the mechanism of the hydrolysis process of nitric esters but a relatively satisfactory theoretical explanation of the phenomenon has been found only recently. 

However, Matsushima [lb] suggested that peroxides may be formed in the course of hydrolysis of nitric esters (4) as transition products prior to the formation of aldehydes (5) ... 

According to Fanner [38] the first stage of hydrolysis proceeds in accordance with the eqn. (1) (p. 7). Afterwards, the products react with one another to form nitrous acid or nitrites and the series of compounds ennumerated above. Fanner s hypothesis seems unsatisfactory when hydrolysis of nitric esters is carried out in a neutral medium since, for example, if ethyl alcohol is treated with an aqueous solution of potassium nitrate no oxidation of the ethyl alcohol occurs even if the mixture of compounds is boiled. 

The above mentioned authors also established that the nitrate ion (in contrast with the nitrite ion) slowly undergoes reduction in the presence of sodium hydrosulphide. This leads to the conclusion that the nitrite ion formed during the hydrolysis of nitric esters cannot be produced by the reduction of a nitrate ion. Hence if the nitrite ion is formed direct during the hydrolysis of nitric esters, then it could only be produced by breaking the linkage between the oxygen and nitrogen atoms. 

Since in numerous cases of hydrolysis of nitric esters the presence of a large amount of nitrate ion has been established, which could be liberated only by rupture of the C—0 bond, the factors that influence the direction of this process should be discussed. Several investigations have thrown light on this problem, which is more complicated than with carboxylic esters, since during the hydrolysis of the latter compounds whether in acid or in alkaline medium only rupture of the ester bond can take place. This has been established in various ways including the use of water containing an 180-isotope. In general the hydrolysis of carboxylic esters can be defined by the equation ... 

The simplest and most commonly used method of preparing nitric esters consists in the O-nitration reaction of alcohols with nitric acid, usually in the presence of sulphuric acid. The reaction is accompanied by reversible hydrolysis, which is typical of esterification reactions. It is very likely that the main nitrating agent is the nitronium ion NO (nitryl cation). It acts through electrophilic substitution. The presence of sulphuric and perchloric acids in the esterifying mixed acid favours the esterification, as it increases the concentration of NO ion. 

When acting with dinitrogen tetroxide on ethylene oxide and homologues followed by hydrolysis a nitric ester of the type (IV) is formed (Pujo etal. [108], Rossmy [75]). 

According to Kohler and Marquc>Tol calcium carbonate does not affect the test directly, but in presence of water it gives rise to hydrolysis of nitrocellulose and forms traces of calcium nitrite, which lower the test. If, however, the conditions be closely adhered to, it Serves a useful purpose, especially in the manufacture of nitric esters. It is also very simple to apply ... 

Dr Robertson (Journ. Soc. Chem. Ind.i, 16th July 1906) has shown the advantage of acidify in the earlier boilings for promoting rapid hydrolysis of the mixed sulphuric and nitric esters. 

Physical properties Dipole moments Spectroscopy Hydrolysis of nitric esters Reduction of nitric esters Some 4>thcr reactions of nunc esters Form Jlion of nitric esters Nitric esters as explosives C hemical stability... 

The H-NMR spectrum of the tetramethyl ester (4b) formed from streptonigrinic acid showed the presence of a primary amino group (2H, 7.84 5, exchangeable with D2O) and treatment of (4b) with nitric acid gave the desaminotetraacid (5) after ester hydrolysis. Thermal decarboxylation of (5) over soda lime produced 5-methyl-2,2 -bipyridyl (6) identical with an authentic sample. 

Methylation of streptonigric acid (3a) yielded methylether ester (3b), which upon basic ester hydrolysis gave triacid (10). Oxidation of (10) with hot basic permanganate afforded the known 2,3,4-trimethoxybenzoic acid (11). The exact position of the phenolic group in the D-ring of streptonigrin was cleverly determined by conversion of the trideuterio-methyl ether (12), prepared from streptonigric acid, to the undeuterated benzofuran (13) upon treatment with nitric acid. 

---