N-nitroso compounds. Part 3. Hydrolysis of N,N′-dimethyl-N′-(p-nitrophenyl)-N-nitrosourea in aqueous basic solution. Effect of a cationic micelle on the hydrolysis of substituted N-nitrosourea

Abstract

The hydrolysis of the title N-nitrosourea has been studied kinetically in various amine buffers (pH 8–11) at 36.8 °C. The reaction proceeds through hydroxide ion attack at the carbonyl carbon to form a tetrahedral intermediate, which collapses to an arylcarbamate ion, releasing an N-nitrosamino fragment. The effect of the buffer concentration on the hydrolysis rate is explained in terms of general base catalysis. Nucleophilic attack of unhindered amines at the carbonyl carbon also occurs under the hydrolytic conditions. With bulkier amines, however, the concurrent nucleophilic reaction is excluded because of steric hindrance around the carbonyl group. The micellar effect on the hydrolysis rate has also been investigated using cetyltrimethylammonium bromide (CTABr). The rate enhancement of the hydrolysis by the CTABr micelle is shown to be six-fold at pH 8.05. However, with an alternative N-nitrosourea bearing a labile hydrogen on N′, a much larger micellar catalysis was observed for the elimination of the hydrogen in the presence of OH^–.