Nitric esters formation

According to Karpukhin and Chetyrkin [49] the nitrolysis of hexamine may proceed with the formation of trihydroxymethylamine nitric ester (XVI) ... 

Action of DPhA on NC and on other organic nitrates was examined in France by several investigators such as Demougin Landon (Ref 14), Muraour (Ref 15) and others. Muraour found that NC is attacked in storage by NC and by other nitric esters (such as PETN) with formation of mono- and poly-nitroderivatives of DPhA. When DPhA was replaced by Centralite 1 (N,N -diethyl-N,N -diphenylurea), which has no mobile H, no reaction occurred, and for this reason Muraour preferred Centralite to DPhA. 

Klason and Carlson were of the opinion that the formation of nitrous acid takes place owing to the peroxy structure of nitric esters, as these, under the influence of a hydrolysing agent, would change their structure and be transformed into peroxy compounds. Simultaneously nitrous acid would be formed ... 

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) ... 

It is necessary to take into consideration the fact that the decomposition of nitric esters has an autocatalytic character water and nitrogen dioxide formed during the decomposition lead to the formation of nitric and nitrous acids which accelerate the reaction of decomposition of the nitric ester. The influence of nitric acid on the rate of decomposition of nitroglycerine was studied by Roginskii [79] and is described below. 

The action of concentrated sulphuric acid and the formation of mixed sulphuric-nitric esters, as well as the action of nitric add and mixtures of nitric—sulphuric acid and water and of hydrochloric acid have been discussed above. Concentrated hydriodic acid of 1.5 density decomposes nitroglycerine to glycerol and nitric oxides. 

E N - O) may be deduced from the heat of formation of hydroxyh amine, NH2OH. This is not very reliably established and the heat of vaporization must be estimated, sc the resulting value of E N 0), 39 kcal, may not be very accurate. It is also possible to estimate E(N -O) by noting that the heat of atomization of a nitric ester is greater than that of the corresponding nitrocompound by E C - O) + E 0 - N) E C - N). Using the figures... 

The sensitiveness and number of chemical changes is greatly augmented by the presence of an alkyl radical in the para position, facilitating, probably, the formation of nitric esters. (R-NO(OH)2). 

The acidity of the mixed acids, not their dehydrating power, has been established as being the rate criterion for the formation of true nitro compounds that it might be extended to the case of nitric esters seems a reasonable assumption. ... 

One of the arguments against the existence of micelles in solutions of cellulose derivatives is the fact that when cellulose is converted into its derivative, e.g. an ester, the degree of polymerization remains almost unchanged. This however only occurs when ester formation is carried out under strictly controlled conditions (nitration at low temperature with nitric and phosphoric acids mixture — p. 341, or with nitric, acetic acids and acetic anhydride mixtures — p. 344). The relevent data found by Staudinger and Mohr [32] are collected in Table 40. 

Complete hydrolysis of h3 uronic acid with mineral adds produces D-ghicosamine, acetic add, and carbon dioxide, the last named indicating the presence of a uronic acid. The latter compound was identified as d-g ucuronic acid by oxidation with nitric add, which led to the formation of D-glucaricacid. D-Glucuronic add was subsequently isolated after enzymic degradation. The carboxyl group of the uronic moiety is free, as shown by salt formation, titration, and the positive hydroxamic test after ester formation. 

Belkner et al. [32] demonstrated that 15-LOX oxidized preferably LDL cholesterol esters. Even in the presence of free linoleic acid, cholesteryl linoleate continued to be a major LOX substrate. It was also found that the depletion of LDL from a-tocopherol has not prevented the LDL oxidation. This is of a special interest in connection with the role of a-tocopherol in LDL oxidation. As the majority of cholesteryl esters is normally buried in the core of a lipoprotein particle and cannot be directly oxidized by LOX, it has been suggested that LDL oxidation might be initiated by a-tocopheryl radical formed during the oxidation of a-tocopherol [33,34]. Correspondingly, it was concluded that the oxidation of LDL by soybean and recombinant human 15-LOXs may occur by two pathways (a) LDL-free fatty acids are oxidized enzymatically with the formation of a-tocopheryl radical, and (b) the a-tocopheryl-mediated oxidation of cholesteryl esters occurs via a nonenzymatic way. Pro and con proofs related to the prooxidant role of a-tocopherol were considered in Chapter 25 in connection with the study of nonenzymatic lipid oxidation and in Chapter 29 dedicated to antioxidants. It should be stressed that comparison of the possible effects of a-tocopherol and nitric oxide on LDL oxidation does not support importance of a-tocopherol prooxidant activity. It should be mentioned that the above data describing the activity of cholesteryl esters in LDL oxidation are in contradiction with some earlier results. Thus in 1988, Sparrow et al. [35] suggested that the 15-LOX-catalyzed oxidation of LDL is accelerated in the presence of phospholipase A2, i.e., the hydrolysis of cholesterol esters is an important step in LDL oxidation. 

It is not only the esters of organic acids which combine, in the manner of the ethyl acetoacetate synthesis , with the enolates of ketones and of esters an analogous behaviour is shown by the esters of nitrous and nitric, acids. The process which leads to the formation of isonitroso-and atinitro-compounds yields products fundamentally similar to those already described just as with ethyl acetate the group CO.CHs enters, so here, the NO- and N02-groups are involved, and enolise " exactly as does >O=0 ... 

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