A photo-ionization study of organosulfur ring compounds: Thiirane,thietane and tetrahydrothiophene

The gas phase heats of formation of several organosulfur cations were determined from thiirane, thietane and tetrahydrothiophene precursor molecules by photoionization mass spectrometry. Heats of formation at 0 K and 298 K are reported for the following ions: H₂CS]^+˙, H₃CS]⁺, C₂H₃S]⁺, C₂H₄S]^+˙, C₃H₅S]⁺, C₃H₆S]^+˙, C₄H₇S]⁺ and C₄H₈S]^+˙. The C₄H₇S]⁺ (m/z 87), C₂H₄S]^+˙ (m/z 60), C₂H₃S]⁺ (m/z 59), C₄H₇]⁺ (m/z 55), C₄H₆]^+˙ (m/z 54) and CH₂S]^+˙ (m/z 46) ions are produced from metastable tetrahydrothiophene ions at photon energies between 10.2 and 10.7 eV. Decay rates of internal energy selected parent ions to the m/z 60, 59, 55 and 54 fragments were measured by threshold photoelectron-photoion coincidence, the results of which are compared to statistical theory (RRKM/QET) calculations. The C₂H₄S]^+˙ ion from tetrahydrothiophene is found to have the thioacetaldehyde structure. From the measured C₂H₄S]^+˙ onset a ΔH = 50±8 kJ mol^?1 was calculated for the thioacetaldehyde molecule.