Stability and structure of benzene dimer cation (C6H6)+2in the gas phase

摘要

The gashyphen;phase equilibria of the clustering reaction (C6H6)+nminus;1+C6H6=(C6H6)+nwere studied with a pulsed electronhyphen;beam highhyphen;pressure mass spectrometer. The enthalpy changes minus;Dgr;H0nminus;1,nfor the reaction withn=2ndash;4 were determined to be 20.6plusmn;1.0, 7.8plusmn;0.5, and sim;7 kcal/mol, respectively. The structure of dimer cation (C6H6)+2was determined byabinitiospinhyphen;restricted openhyphen;shell Hartreendash;Fock molecular orbital (ROHF MO) calculations. Two isomers, lsquo;lsquo;axial C2rsquo;rsquo; and lsquo;lsquo;parallel C2v, rsquo;rsquo; are calculated to be located at the potentialhyphen;energy minima. The axial C2is 3.0 kcal/mol more stable than the parallel C2vby ROHF/6hyphen;31Gast;ast;//ROHF/3hyphen;21G.