A combined experimental and theoretical investigation of the formation, thermodynamic stability, and chemical reactivity of neutral and ionic organic fragments in the gas-phase will be made. This study will measure sequential carbon-carbon and carbon-hydrogen dissociation energies for simple organic compounds such as cyclopropane, benzene, toluene, and naphthalene, and characterize the gas-phase reactivity of selected ionic fragments involved in the bond-by-bond disassembly of these molecules. A flowing afterglow-guided ion beam instrument will be used to measure activation energies for collision-induced dissociation reactions of selected carbynes, biradicals, triradicals, and their corresponding negative ions. These data will allow an examination of thermochemical issues such as the energetic consequences of electronic promotion (hybridization) effects in chemical bonding, the intrinsic Bronsted acidities of radicals and carbenes, the relative magnitudes of the first, second, and third carbon-hydrogen bond dissociation energies in benzene and related aromatic compounds, and the energetic benefit of through-bond coupling and spin polarization effects in organic biradicals. %%% This grant from the Organic Dynamics Program supports the continuing work of Professor Robert R. Squires at the Purdue University. This study will measure sequential carbon- carbon and carbon-hydrogen bond dissociation energies of some simple organic molecules and characterize the gas-phase reactivity of selected ionic fragments involved in this bond- by-bond disassembly. These experiments will provide new thermochemical data for neutral and ionic carbon-centered reactive intermediates. Analysis of these data will allow an evaluation of some important theoretical concepts in chemistry, which include chemical bonding and acidity of molecules.
