Enantioselective HF loss promoted by resonant two-photon ionization of supersonically expanded (R)-1-phenyl-2,2,2-trifluoroethanol clusters.

ABSTRACT

(R)-1-phenyl-2,2,2-trifluoroethanol and its hydrogen bonded adducts with achiral (water, tetrahydrofuran) and chiral solvent molecules ((R)- and (S)-butan-2-ol, (R)- and (S)-3-hydroxy-tetrahydrofuran) have been ionized by resonant two-photon absorption. The presence of photofragments, attributable to the occurrence of a hydrogen fluoride loss reaction, has been interpreted with the aid of theoretical predictions at the DFT level of theory with the inclusion of dispersive terms. The HF elimination process takes place by a mechanism involving the preliminary C(alpha)-H hydrogen transfer to an hydroxyl oxygen assisted by the solvent molecule which is followed by extrusion of the HF molecule. The calculated energy barriers depend on the type of solvent as well as on its configuration and are consistent with the observed fragmentation ratios.