KINETIC STUDIES ON THE FORMATION OF NITROSOCOMPOUNDS .2. FORMATION OF N-NITROSO-N-METHYLUREA IN AQUEOUS-SOLUTION OF PERCHLORIC-ACID

The kinetics of nitrosation of Methylurea (MU) in aqueous perchloric solution has been studied using two techniques: a dynamic spectrophotometric and a stopped-flow technique. The rate law obtained, when pH was varied in the range 0.27-3.22, is {Mathematical expression} where [MU] and [nitrite] represent stoichiometric concentrations. At 288.0 K and μ=1.0 M, f=(15.6±0.5)M-2s-1 and g=(1.06±0.08) 10-3M. This rate law becomes independent of the acidity of the solution when this is increased ([ClO4H])>1.00 M). These results together with the activation of the nitrosation rate by the ionic strength and the negative value of the activation entropy shown that only the NO2H2+ or NO+ is the effective carrier for the nitrosation. Comparisons with the nitrosation of dimethylamine were also made leading to the conclusion that there is no simple explanation for the fact that the nitrosation via NO2H2+/NO+ disappears when the nitrosable compound is of increased basicity. © 1979 Springer-Verlag.