Proton affinity of some radicals of alcohols, ethers and amines
Résumé
Calculated proton affinities (PA) of the CH3*CHX (X=OH, OCH3, and NH2) a-radicals and of four ß-radicals *CH2CH2X (X=OH, OCH3, OCH2CH3, and NH2) confirm that PA of a-radicals lie far below those of the corresponding saturated molecules and indicate, as a first and rough evaluation, that a radical in the ß-position, has a negligible influence on the PA at the heteroatom. Experiments were performed to measure the PA of ß-radicals both by measuring the rates of deprotonation of the corresponding ß-distonic ions in a FT-ICR cell and by determining the ?Hf[*CH2CH2XH+], itself obtained by appearance energy (AE) measurements, using synchrotron radiation. From these results and those of literature, the following values are proposed: PA[*CH2CH2OH]=185.8±0.5kcal/mol, PA[*CH2CH2OCH 3]=193.3±0.5kcal/mol and PA[*CH2CH2NH2]=116±1kcal/mol. © 2003 Elsevier Science B.V. All rights reserved.