Experimental and theoretical studies of isolated neutral and ionic 2-propanol and their clusters.

Infrared plus vacuum ultraviolet (IR/VUV) nonresonant photoionization spectroscopy and VUV/IR photodissociation spectroscopy are employed to study fragmentation pathways and structures of neutral and ionic 2-propanol ((CH(3))(2)CHOH) (IPA) and their relevant clusters of size up to the pentamer. Only the gauche monomer is generated in the supersonic expansion; its VUV induced fragmentation pathways involve C(alpha)-C(beta) bond dissociation. The clusters consist of both gauche and trans conformers and their VUV induced fragmentation pathways are size dependent. The IR spectra of neutral clusters (IPA)(n) suggest that the dimer has a chainlike structure, whereas larger clusters have cyclic structures. VUV ionization of the neutral gauche 2-propanol generates two parent cation isomers whose C(alpha)-C(beta) bond dissociations are facilitated by excitation of the OH vibrations. The IR spectra of ionic molecular complex clusters (IPA)(n-1)CH(3)CHOH(+) and protonated clusters (IPA)(n-1)H(+), generated by VUV ionization of neutral clusters, show that both cluster types adopt open structures with at least one free OH group. Qualitative structural assignments are generated for the neutral species based on MP2/aug-cc-pVDZ, MP2/6-31G, and B3LYP/6-31+G(d) calculations.