Constant-Rate Titrations in Studies of Chemical Kinetics. General Technique for the Elucidation of Reaction Mechanisms and the Evaluation of Rate Constants. Titration of Nitromethane with Sodium Hydroxide

A multiparametric curve-fitting procedure employing numerical integration of the rate equation may be used to evaluate the rate constants for any reaction scheme on the basis of data obtained in constant-rate titrations. It is immaterial whether the rate equation can be solved In closed form or not. Deviation-pattern recognition shows whether the assumed reaction scheme provides a satisfactory fit to the data, and can guide a search for a better hypothesis. With data obtained in thermometric titrations of nitromethane with sodium hydroxide, the procedure shows that assuming the titration reaction to be irreversible does not yield an acceptable fit, guides the selection of a reversible reaction as yielding a much better one, and provides values of the rate and equilibrium constants of the reaction CH₃NO₂ + OH^- ⇄ CH₂=NO₂^- + H₂O that are in acceptable agreement with those in the prior literature.