Rearrangements and fragmentations of metastable [C13H9S]+, [C14H11]+, [C13H11]+ and [C8H7S]+ ions

[C₁₃H₉S]⁺, [C₁₄H₁₁]⁺, [C₁₃H₁₁]⁺ and [C₈H₇S]⁺ ions with unknown structures were generated from two [C₁₄H₁₂S]^+·precursor ions by fragmentation reactions that must be preceded by extensive rearrangements. Ions with the same compositions, each with several initial structures, were prepared by simple bond-breaking reactions. Metastable characteristics were compared for each of the four types of ions. It was found than in all cases fast isomerization reactions occur prior to fragmentation, so that no information about the unknown ion structures could be obtained by comparison of the observed fragmentations of metastable ions.     

Isomerization study of C5H5NO molecules

The complex potential energy surface (PES) for the isomerization of C₅H₅NO species, including 18 isomers and 23 interconversion transition states, is probed theoretically at the B3LYP/6‐311++G(d,p) and MP2//B3LYP/6‐311++G(d,p) levels of theory. The geometries and relative energies for various stationary points were determined. The zero‐point vibrational energy (ZPVE) corrections have been made to calculate the reliable energy. We predicted a six‐membered ring structure as a global minima isomer I, which is 118.49 and 131.48 kcal · mol^?1 more stable than the least stable, four‐ and three‐membered ring isomer VIII at B3LYP and MP2//B3LYP levels of theory, respectively. The isomers and interconversion transition states have verified by frequency calculation. The intrinsic reaction coordinates (IRC) calculations have been performed to confirm that each transition state is linked by the desired reactants and products. The isomer stability has been studied using relative energies, chemical hardness, and chemical potential. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007