Kinetics of Solvolyses of Various N, N'-Dialkyl-N-nitrosoureas in Neutral and Alkaline Solutions

Abstract

a) The neutral and alkaline solvolyses of N-methyl-N'-p-fluorophenyl-N-nitrosourea, 1, 6-dimethyl-1, 6-dinitrosobiurea, N-methyl-N'-phenethyl-N-nitrosourea, trimethylenebis-N-methyl-N-nitrosourea and N, N'-dimethyl-N-nitrosourea are subject to spontaneous and specific hydroxide ion catalysis, i.e. k_app(sec^-1=k₀+k_OH[OH^-]. The decreasing order of reactivity is in the order given and is consistent with the fact that electron-with-drawing substituents abet hydroxyl ion attack by inducing a more positive center. The fact that substitution of an alkyl for a hydrogen on the N'-nitrogen inhibits hydrolysis favors the adjacent carbonyl carbon as the primary focus of hydroxide ion attack. b) The log k-pH profiles of N, N'-dimethyl-N-nitrosourea and 1, 6-dimethyl-1, 6-dinitrosobiurea show a deviation in the linearity of the alkaline branch which can be attributed to a kinetic pKa' where these compounds may exist as anions at higher pH values and thus be more resistant to hydroxide ion attack. c) The gas chromatographically analyzed alcohol products of alkaline degradation of N-alkyl-N'-nitrosourease are various in several cases and thus clearly implicate a potentiallu rearranging carbonium ion intermediate in the alkaline solvolyses of these compounds. The N-n-butyl compound gives a mixture of n-butyl-alcohol in 45% yield, and secondary butyl alcohol in 24% yield for pH values greater than 7.0. The fact that the N-isobutyl compound yields t-butyl alcohol (76%), sec-butyl alcohol (22%)and isobutyl alcohol (18%) also implicates a methyl shift. The N-alkyl-and N-benzyl-compounds yield only the corresponding alcohols.