Acyl nitrate

Nitration in acetic anhydride, or in solutions of dinitrogen pentoxide or of other acyl nitrates in carbon tetrachloride, has been associated with a higher ratio of o- to 7)-substitution in the reactions of certain com-... 

These features serve to distinguish nitration in acetic anhydride from nitration in inert organic solvents. With other acyl nitrates less work has been done, and it is convenient to deal first with the case of benzoyl nitrate. 

When nitration of pyridazine iV-oxides is carried out with acyl nitrates (prepared in situ from acyl chlorides and silver nitrate) the reaction takes place at the /3-position relative to the iV-oxide group. Under these circumstances only mononitro derivatives are formed. For example, nitration of pyridazine 1-oxide with acetyl nitrate yields 3-nitropyridazine 1-oxide (17%) and 5-nitropyridazine 1-oxide (0.8%), whereas with benzoyl nitrate a better yield of 5-nitropyridazine 1-oxide is obtained. 

For nitrating on the lab scale, mixts of nitric acid esters or acyl nitrates, eg acetyl nitrate (CH3CONO3) and sulfuric acid may also be used... 

Where direct nitration results in degradation, a primary amine can be acylated, nitrated directly to form a secondary niiramine, which is then hydrolyzed to form the primary nitramine as exemplified in the following reaction sequence ... 

See related ACID ANHYDRIDES, ACYL NITRATES, PEROXYESTERS... 

Attempts to follow a published method for nitrating phthalic anhydride in sulfuric acid at 80-100°C with fuming nitric acid caused an eruptive decomposition to occur after 2 h delay [1], The hazard can be eliminated by use of a smaller excess of nitrating acid at 55-65°C [2], Acyl nitrates were suggested as a possible cause of the delayed eruption [3],... 

Nitration of ketones or enol ethers provides a useful method for the preparation of a-nitro ketones. Direct nitration of ketones with HN03 suffers from the formation of a variety of oxidative by-products. Alternatively, the conversion of ketones into their enolates, enol acetates, or enol ethers, followed by nitration with conventional nitrating agents such as acyl nitrates, gives a-nitro ketones (see Ref. 79, a 1980 review). The nitration of enol acetates of alkylated cyclohexanones with concentrated nitric acid in acetic anhydride at 15-22 °C leads to mixtures of cis- and rrans-substituted 2-nitrocyclohexanones in 75-92% yield. 4-Monoalkylated acetoxy-cyclohexanes give mainly m-compounds, and 3-monoalkylated ones yield fra/w-compounds (Eq. 2.40).80... 

Several metal oxides could be used as acid catalysts, although zeolites and zeo-types are mainly preferred as an alternative to liquid acids (Figure 13.1). This is a consequence of the possibility of tuning the acidity of microporous materials as well as the shape selectivity observed with zeolites that have favored their use in new catalytic processes. However, a solid with similar or higher acid strength than 100% sulfuric acid (the so-called superacid materials) could be preferred in some processes. From these solid catalysts, nation, heteropolyoxometalates, or sulfated metal oxides have been extensively studied in the last ten years (Figure 13.2). Their so-called superacid character has favored their use in a large number of acid reactions alkane isomerization, alkylation of isobutene, or aromatic hydrocarbons with olefins, acylation, nitrations, and so forth. 

Using acyl nitrates as nitrating agents (compare with Section 4.5.4.2) and zeolite H-ZSM-11 treated with tributylamine, Nagy et al. (1991, 1994) were able to nitrate toluene with an even more impressive percentage of the isomers obtained—ortho 2-3%, meta 1-2%, and para 95-98%. 

Bachmann and Biermann reported the synthesis of nitroalkanes from the thermolysis of acyl nitrates. The thermolysis of nitrite and nitrate esters over an asbestos catalyst is also reported to yield nitroalkanes. ... 

Acyl nitrates react with low molecular weight aliphatic alcohols to give the alkyl nitrate ester and the corresponding carboxylic acid. " ... 

Product contains 10% acyl nitrate impurity. Product contains < 5% acyi nitrate impurity. Product is readily hydrolyzed. Bulk of the product mass is poiymeric materiai. 

Isoquinoline (pK 5.4) has similar basicity to quinoline and pyridine, and also undergoes A -alkylation and A -acylation. Nitration occurs... 

Electrophilic aromatic substitution is a reaction where a hydrogen atom in an aromatic system, e.g. benzene, is replaced by an electrophile. Some of the important electrophilic substitution reactions are Friedel-Crafts alkylation and acylation, nitration, halogenation and sulphonation of benzene. 

Acyl Nitrates and Perchlorates arc described by M.Schmeisser, AngewChem67,493-501 (1955)... 

Nitration of pyridazine A-oxides with acyl nitrates prepared from acyl chlorides and silver nitrate also occurs at the (3-position relative to the /V-oxide group. Thus, pyridazine 1-oxide yields 3-nitropyridazine 1-oxide. 

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