Alkaline hydrolyses of alkyl nitrites and related carboxylic esters

Abstract

Alkaline hydrolysis of alkyl nitrites and related carboxylic esters was investigated. Marked differences between alkyl nitrites and the corresponding esters in hydrolysis are as follows. (1) Alkaline hydrolysis of alkyl nitrite is much slower than that of the corresponding ester. (2) However, acid hydrolysis of alkyl nitrite is markedly faster than that of the corresponding ester. (3) There is no concurrent oxygen exchange between the nitroso-oxygen of n-hexyl nitrite and hydroxide in alkaline hydrolysis at 45.0 and 55.1°C. (4) The polar effect of substituents on the leaving alkoxide group in alkaline hydrolysis of alkyl nitrites is roughly two-fold larger than that for the esters, i.e.ρ° 1.46 for substituted benzyl nitrites, 0.994 for substituted benzyl benzoates, 0.764 for substituted benzyl acetates ρ* 2.54 for alkyl nitrites, 1.26 for alkyl benzoates, 1.28 for alkyl acetates. (5) The steric requirements for alkaline hydrolysis of alkyl nitrites are less than those for the esters, i.e. Taft δ-values 1.03 for alkyl nitrites, 1.52 for alkyl benzoates, 1.50 for alkyl acetates. These differences are rationalized in terms of the two main differences of the electrophilic centres, (1) the greater electronegativity of nitrogen than of carbon, and (2) the presence of a lone pair on nitrogen but not on carbon.