Miscellaneous Thermochemical Studies

Several studies were aimed at determining the thermochemistry of additional species of potential importance in plasma systems. One of these (Fisher and Armentrout, 1990c) involved studying the reaction of Oj( Ilg, v = 0) with CH4. Analysis of the kinetic energy dependence of the slightly endothermic reactions (23) and (24), 

Finally, a comprehensive study of the thermochemistry of sulfur fluoride cations and neutrals was performed (Fisher et al., 1992). Endothermic charge-transfer reactions of several of the SF+ ions were examined. Analyses of these cross sections yielded the ionization energies of SF from reactions with Xe of SF3 from reactions with CH3I, NO, and C HsBr of SF4 from reactions with Xe and O2 and of SF5 from reactions with NO, C6H5CF3, and CH3I. IE(SF2) was not measured in our work, as a precise photoelectron value (10.08 0.05 eV) was already available in the literature (DeLeeuw et al., 1978). Some of our values 

We also examined the energy dependence of the cross sections for CID of SF+ (n = 1 to 5) with Xe (Fisher et al., 1992). Analysis of these cross sections yielded the 0-K bond-dissociation energies (BDEs) listed in Table VI. Experimental values in the literature (Chase et al., 1985 Lias et al., 1988) prior to our study had large error bars, but subsequent photoionization studies by Ng and coworkers (Cheung et al., 1995) probably provide the most accmate heats of formation for SFj, SFj, and SF4 that are presently available. The heat of formation for SF has been measured by the same group using a sophisticated photoelectron-photoion coincidence experiment (Evans et al., 1997). BDEs calculated using these values and heats of formation for S+ and SF from 

Bond Dissociation Energies (in eV) of Sulfur Fluoride Cations at 0 K 

Chase et al. (1985) are given in Table VI. These agree nicely with theoretical values (Irikura, 1995 Cheung et al., 1995 Bauschlicher and Ricca, 1998). 

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Despite the interest in, and importance of, sulphonic acids and their salts, osylates and other sulphonate esters, sulphonamides, sulphonyl halides and miscellaneous derivatives such as disulphones, thermochemical data for this class of compounds are disappointingly sparse and often suspect. Thus the data will not be presented in the form of tables, but rather will be discussed one primary reference at a time per subsection. Because the required gas phase data are almost totally absent, we will also not attempt to generate Benson increments1 for groups of interest such as S02(C)(0), as would be part of a thermochemical study of sulphonic acids and their esters but not the isomeric sulphites that contain the SO(0)2 group. As such, this chapter is unlike so many of the other thermochemical chapters in the other volumes of The Chemistry of the Functional Groups series. 

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