Nitrosation of methylformamide (MFA) has been studied kinetically. The results obtained show that the reaction rate is first order with respect to both the MFA and proton concentration. The absence of catalysis by nucleophilic anions and the observed general base catalysis is interpreted in terms of formation of a protonated nitrosamide intermediate, being the proton transfer the slow step of the process. The primary solvent isotope effect observed corroborates this mechanism. From this study, we were able to obtain the values of the rate constants for the nitrosation process. The catalytic constants in the presence of buffers were also obtained and the analysis of the Bronsted slopes suggests a process with a transition state more similar to the reactants than the products. The absence of electron donating groups in MFA leads to a very low value of the bimolecular rate constant of the nitrosation reaction.
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