Hydrolysis of Diazomethane - Kinetics and Mechanism

Article abstract of DOI:10.1021/ja00544a025

The reaction between diazomethane and the hydronium ion was studied in a THF-water (60:40 v/v) mixture at 25 deg C.When a large excess of diazoalkane was used, the kinetics were zero order in diazoalkane and first order in acid for the pH range 4 < pH < 5.5.The pH rose dramatically at the start of the reaction: the pH rise was measured by use of a novel continuous-flow system.Combination of the kinetic and pH data allowed estimation of the protonation rate as 4*10⁸ M^-1s^-1.Isotope-exchange studies showed that water deprotonates the methanediazonium ion less rapidly than it displaces nitrogen; however, the hydroxide ion reacts more rapidly as a base than as a nucleophile.The rates of nucleophilic attack of water and the hydroxide ion on the methanediazonium ion were estimated as 1.8 s^-1 and 1*10⁴ M^-1s^-1, respectively, in THF-water (60:40 v/v).The pKa of the methanediazonium ion in this medium was ten.