Kinetics and thermochemistry of reversible adduct formation in the

J . Phys. Chem. 1990, 94, 2896-2903

2896

Registry No, DMBA, 57-97-6;TEA, 121-44-8; DIPMA, 10342-97-9; DIPEA, 7087-68-5; DEA, 91-66-7; o-PDA, 95-54-5;p-PDA, 106-50-3; DMPD, 99-98-9; TMPD, 100-22-1;p-BQ, 106-51-4;TCNE, 670-54-2; phenanthrene, 85-01-8: 1,3,6,8-tetramethylphenanthrene.18499-99-5;

2,4,5,7-tetramethylphenanthrene,7396-38-5; 3-methoxyphenanthrene, 835-06-3; 3-isopropylphenanthrene,33240-32-3;3-methylphenanthrene, 832-71-3: 3-cyanophenanthrene, 21661-50-7; 9-cyanophenanthrene, 25 10-55-6: naphthalene, 91 -20-3.

Kinetics and Thermochemistry of Reversible Adduct Formation in the Reaction of Ci('P,) with CS, J. M. Nicovich, C. J . Shackelford,+ and P. H. Wine* Molecular Sciences Branch, Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, Georgia 30332 (Receiued: May 15, 1989; In Final Form: November 8, 1989) Reversible adduct formation in the reaction of CI(,P,) with CS, has been observed over the temperature range 193-258 K by use of time-resolved resonance fluorescence spectroscopy to follow the decay of pulsed-laser-generated CI(2PJ) into equilibrium with CS2CI. Rate coefficients for CS2CI formation and decomposition have been determined as a function of temperature and pressure; hence, the equilibrium constant has been determined as a function of temperature. A second-law analysis of the temperature dependence of K p and heat capacity corrections calculated with use of an assumed CS2Clstructure yields the following thermodynamic parameters for the association reaction: = -10.5 A 0.5 kcal mol-', AHoo = -9.5 f 0.7 kcal mol-', = -26.8 f 2.4 cal mol-' deg-I, and AHf,2ss(CS2CI)= 46.4 f 0.6 kcal mol-'. The resonance fluorescence detection scheme has been adapted to allow detection of CI(,P,) in the presence of large concentrations of 02,thus allowing the CS2Cl + 0, reaction to be investigated. We find that the rate coefficient for CS2CI + 0, reaction via all channels that cm3molecule-' s-I at 293 K and 300-Torr total pressure and that the total rate coefficient do not generate CI(,P,) is