Active methylene compounds nitrations, nitric acid

A. Direct Nitration of Active Methylene Compounds with Nitric Acid 16-1. Preparation of Diethyl Nitromalonate... 

A. DIRECT NITRATION QF ACTIVE METHYLENE COMPOUNDS WITH NITRIC ACID... 

Active methylene compounds have been nitrated directly with nitric acid. In this synthesis one or more labile hydrogens are replaced by a nitro group. 

Active methylene compounds have been nitrated directly with nitric acid. Since the nitro group thus introduced also activates the carbon adjacent to it, the product resulting from the direct nitration of an active methylene compound is frequently highly reactive and consequently may be quite unstable—in fact, explosive. Therefore, as with all aliphatic nitro compounds, precaution must be taken to reduce the hazards of explosion to personnel and equipment. A typical example of the reaction is given in the following preparation. 

Nitration by nitric acid in sulphuric acid has also been by Modro and Ridd52 in a kinetic study of the mechanism by which the substituent effects of positive poles are transmitted in electrophilic substitution. The rate coefficients for nitration of the compounds Pl CHi NMej (n = 0-3) given in Table 10 show that insertion of methylene groups causes a substantial decrease in deactivation by the NMej group as expected. Since analysis of this effect is complicated by the superimposed activation by the introduced alkyl group, the reactivities of the... 

Halogenation179 and benzoylation of subtituted benzenes also favor the para-products. Nitration of toluene with mpropyl nitrate in the presence of H-ZSM-5 gives 95% para-selectivity.180 Benzene can be nitrated with 65% nitric acid in the vapor phase at 170°C over a mordenite catalyst.181 (Most zeolites are not stable to protonic mineral acids. Mordenite is an exception.) The nitration of aromatic compounds can also be carried out with a sulfuric acid on silica catalyst that is slurried in methylene chloride to give 97-98% yields.182 The catalyst could be recovered and reused with less than 3% loss in activity after three runs. These methods eliminate the problem of what to do with spent by-product sulfuric acid from conventional nitrations. 

Recently a further method of alkaline nitration has been developed. It involves acetone cyanohydrin nitrate, which is readily obtained from acetone cyanohydrin and fuming nitric acid, and applies to compounds such as aryl-acetonitriles and malonic and acetoacetic esters that contain active methylene groups.130... 

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