Intramolecular solvation of carboxylate anions in the gas phase

Proton exchange reactions between acetate, n-butanoate, 2-ethylhexanoate, a nd n-decanoate were studied experimentally by the use of PHPMS and theoreti cally by the use of ab initio methods. The occurrence of a curvature in som e of the van't Hoff plots suggests isomerization of at least one of the par ticipants in the equilibrium. This isomerization is suggested to be an intr amolecular solvation of the carboxylate anions via unconventional hydrogen bonding. These interactions are discussed in terms of charge distributions in the unfolded and folded conformers of the carboxylates. Thermochemical v alues for the intramolecular solvation were deconvoluted from the curved va n't Hoff plots by a fitting procedure. The thermochemical data for the intr amolecular solvation was used to calculate the conformer composition of the carboxylate anions. Various properties related to the intramolecular solva tion of the carboxylate anions are discussed.