The purification of formamide, and the rate of its reaction with dissolved water

Abstract

Formamide of low water content (0·008–0·01M) and very low specific conductance (2 × 10^–7 ohm^–1 cm.^–1) has been prepared by treating it with 3A molecular sieve and then with a mixed bed of ion-exchange resins loaded, respectively, with H⁺ and HCO·NH^– ions. The success of the method depends in part upon knowledge of the rates of the solvolysis reaction between formamide and small quantities of water dissolved in it, and the kinetics of this reaction were studied with sodium formamide and with sulphuric acid as catalysts. The pseudo-first-order rate constants (with respect to water), although proportional to the amount of catalyst at low catalyst concentrations, decreased at higher ones and actually passed through a maximum at ca. 4M-sulphuric acid. This behaviour closely parallels that of the hydrolysis of small quantities of formamide dissolved in water.