Reevaluation of Arrhenius parameters for H + OH sup minus yields (e sup minus ) sub aq + H sub 2 O and the enthalpy and entropy of hydrated electrons

The rate constant for the reaction H{sup {sm bullet}} + OH{sup {minus}} {yields} (e{sup {minus}}){sub aq} + H{sub 2}O in aqueous solution has been measured in the temperature range 5-70{degree}C by the pulsed EPR free induction decay (fid) attenuation technique. The Arrhenius parameters for the reaction are A = (1.4 {plus minus} 0.4) {times} 10{sup 14} M{sup {minus}1} s{sup {minus}1} and E{sub a} = 38.5 {plus minus} 1.7 kJ/mol (9.2 {plus minus} 0.4 kcal/mol), in sharp disagreement with other work based on a less direct kinetic method. From these values the enthalpy of activation {Delta}H{sup {double dagger}} = 36.1 {plus minus} 1.7 kJ/mol and entropy of activation {Delta}S{sup {double dagger}} = 17.3 {plus minus} 6.0 J/(mol{center dot}deg) are deduced. The combination of this data with Arrhenius parameters for the reverse reaction allows reevaluation of the enthalpy, entropy, and free energy of formation for the hydrated electron.