Reversible reactions of cycloalkane solvent holes. 2. Scavenging of cis- and trans-decalin(center dot+) by benzene

Solvent holes in liquid cis- and trans-decalin form metastable complexes wi th benzene, which are probably solvation complexes of monomer radical catio ns of benzene. At 25 degrees C, the rate constants of formation of the comp lexes are, for trans- and cis-decalin respectively 1.1 x 10(11) and 3.6 x 1 0(10) M-1 s(-1), and the natural lifetime of the complex is 7 ns for trans- and 50 ns for cis-decalin. Thermodynamic potentials for the complexation a re determined. The heat of the complex formation is approximate to-26 kJ/mo l for trans- and approximate to-18 kJ/mol for cis-decalin. In cis-decalin, the complexes are more stable because of near-zero entropy of the complex f ormation. The complex decays by proton or H atom transfer with activation e nergy approximate to 10 kJ/mol (which yields a benzonium cation) or in a re active encounter with a second benzene molecule (which yields a benzene dim er cation). Laser excitation of the dimer cation with a 1.165- or 2.33 eV p hoton causes valence band electron transfer and injection of a free solvent hole.