SOLVENT AND TEMPERATURE EFFECTS ON THE RATE CONSTANTS OF SOLVOLYSIS OF TERT-BUTYL BROMIDE IN MONO-ALCOHOL AND DI-ALCOHOL

Rate constants, k, for the solvolytic reactions of 2-bromo-2-methylpropane (Bu(t)Br) in the monoalcohols propan-1-ol and butan-1-ol and in the dialcohols ethane-1,2-diol, propane-1,3-diol and butane-1,4-diol are reported, at different temperatures. These values, the Arrhenius activation energies, E(a), and the thermodynamic functions of activation, Gibbs energy (DELTA-G-degrees-Kelvin), enthalpy (DELTA-H-degrees-Kelvin) and entropy (DELTA-S-degrees-Kelvin) are interpreted and compared with previous results in methanol and ethanol. According to the Intersecting-state model, the reaction-energy profile is shaped and the solvent effect on the Gibbs energy of activation, DELTA-G-degrees-Kelvin, is analysed. At the molecular level, the dominant solvent-solute interactions are examined. The results show that changes in E(a) (or DELTA-H-degrees-Kelvin) most affect the changes in the k values when dialcohols are used in place of monoalcohols; DELTA-S-degrees-Kelvin seems to control the differences in the k values within the set of monoalcohols.