Kinetics of solvated electrons in reaction with hexamethylphosphoric triamide

Abstract

Solvated electrons, e_s^–, have been generated in hexamethylphosphoric triamide (HMPA) by chemical and electrochemical means. When Na metal was used to release e_s^–, two distinct bands, already reported in the literature, appeared in the absorption spectrum of the solution, which rapidly turned red–brown and decomposed according to irreproducible complex kinetics which could not be analysed. When Li was used instead of sodium, a single broad band extending into the IR region developed and later decayed obeying consistently first-order kinetics in absorbance. Kinetic rate constants are reported and half-lives at ambient temperature were about 1 h duration. A systematic study of the disappearance of solvated electrons in HMPA was carried out at several temperatures (from 7 to 27 °C) and an activation energy (85–89 kJ mol^–1) is estimated both in the absence and in the presence of lithium perchlorate. However, the overall reaction rate is markedly increased in the presence of Li⁺; a mechanism is proposed to account for this lithium salt effect.