The basis 3df2df in Table 1 again contains one set of $functions on all heavy atoms. Second row atoms carry three sets of &functions but first row atoms only two. When this basis set is used instead of 6-31 lG(2dJp) the atomization energies of C10, OC10, and ClOO are all in acceptable agreement with experiment.The basis 3df2df has been applied to two further test molecules and to the C103-isomers. For all species in Table 1 but ClOCl the deviation is less than 5 kcalfmol.The G1 calculations on C103-isomers were started with geometry optimizations on the HF/6-31G*-and MP2f6-31G*-levels of theory. All three supposed isomers, C1000, OC100, and sym-C103 were found as minima [9] on the potential energy hypersurface. The GI total energy calculations using the basis set described above gave heats of formation of 41, 58, and 48 kcalfmol, respectively.From these ab initio calculations it appears that ClOOO might be considered as an intermediate in reaction (1). Since it is a real minimum on the potential energy hypersurface, there must exist a barrier for the exothermic dissociation of ground state ClOOO into C10 and 02.The work was supported in part by the BMFT, Bonn, withinThe authors acknowledge access to the facilities of the Hochstproject 0744120 0.leistungsrechenzentrum Julich. References Howard SidebottomUniversity College Dublin, Ireland Chemical Kinetics f Elementary Reactions f RadicalsRate constants for the gas-phase reactions of ozone with a series of alkenes have been determined using a conventional static system. Ozone loss was monitored in excess of the hydrocarbon and rate data measured at 1 atmosphere total pressure over the temperature range 240-324 K. The Arrhenius parameters obtained are discussed in terms of structure-reactivity relationships. Product studies have been carried out for the reaction of O3 with the conjugated dienes, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene) and 2,3-dimethyl-1,3-butadiene in air. The results provide information on the decomposition pathways for the primary ozonides and the relative importance of ozone addition to the two doublebonds in isoprene.cant reactivity towards ozone as well as towards hydroxyl and nitrate radicals. Numerous potentially important roles of the ozone-alkene reaction have been recognized since these reactions can provide mutual sinks for both ozone and alkenes and concomitantly serve as sources of partially oxidised compounds e. g. CO, aldehydes, ketones and organic

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The gas phase reaction of OH radicals with dimethyl sulfide (CH,SCH,, DMS) has been studied using both an absolute and a relative technique a t 295 2 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 t 0.2) x cm3 molecule-' sK1 was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.

Rate constants for the reactions of OH radicals and C1 atoms with diethyl sulfide (DES), din-propyl sulfide (DPS), and di-n-butyl sulfide (DBS) have been determined at 295 ? 3 K and a total pressure of 1 atm. Hydroxyl radical rate data was obtained using the absolute technique of pulse radiolysis combined with kinetic spectroscopy. The chlorine atom rate constants were measured using a conventional photolytic relative rate method. The rate constant for the reaction of C1 atoms with dimethyl sulfide (DMS) was also determined. The following rate constants were obtained:k(C1 + DES) = (44.1 5 4) X 1 0 . ' ' cm3 molecule-'s-' k(C1 + DPS) = (51.8 5 41 x lo-" cm3 molecuIe-'s-' k(C1 + DBS) = (64.6 5 2) X lo-" cm3 molecule-' s-l

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