Proton affinity of some radicals of alcohols, ethers and amines

Abstract

Calculated proton affinities (PA) of the CH 3 CHX (X=OH, OCH 3, and NH 2) α-radicals and of four β-radicals CH 2CH 2X (X=OH, OCH 3, OCH 2CH 3, and NH 2) confirm that PA of α-radicals lie far below those of the corresponding saturated molecules and indicate, as a first and rough evaluation, that a radical in the β-position, has a negligible influence on the PA at the heteroatom. Experiments were performed to measure the PA of β-radicals both by measuring the rates of deprotonation of the corresponding β-distonic ions in a FT-ICR cell and by determining the Δ H f[ CH 2CH 2XH +], itself obtained by appearance energy (AE) measurements, using synchrotron radiation. From these results and those of literature, the following values are proposed: PA[ CH 2CH 2OH]=185.8±0.5 kcal/mol, PA[ CH 2CH 2OCH 3]=193.3±0.5 kcal/mol and PA[ CH 2CH 2NH 2]=116±1 kcal/mol.