On Gas Phase α-Effects. 1. The Gas-Phase Manifestation and Potential SET Character

The possibility of a gas-phase α-effect has been explored for the methyl transfer from methyl formate to hydroxide, hydroperoxide, and ethoxide by computing barrier heights at the HF/6-311++G(2df,2p) level of theory. The α-nucleophile (hydroperoxide) is found to have a lower barrier than the gas-phase-acidity-matched normal nucleophile (ethoxide) by 3.6 kcal/mol, offering evidence for a gas phase α-effect. A Shi−Boyd analysis for these reactions indicates that there is more single-electron-transfer character in the hydroperoxide transition state than for either hydroxide or ethoxide, further bolstering the existence of a gas-phase α-effect and the appropriateness of the Hoz model for the α-effect.