Infrared Chemiluminescence Studies of the H + (CH3)3COCl and H + RC(O)SCl (R = Cl, F, OCH3) Reactions: Observation of OCS Infrared Chemiluminescence

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Infrared chemiluminescence from a room-temperature flow reactor was used to study the reactions of H atoms with (CH3)3COCl, ClC(O)SCl, FC(O)SCl, and CH3OC(O)SCl. Infrared emission spectra were recorded from the HCl, HF, and OCS products. The anharmonic shifts from bands involving ν1, ν2, and ν3 excitation are too small to obtain information about bending vs stretch excitation of OCS from the Δv3 = −1 spectra; however, a computer simulation method was developed to analyze the Δv3 = −1 transition to assign the average total vibrational energy of OCS, 〈Ev(OCS)〉. The enthalpy changes for the carbonylsulfenyl chloride reactions were estimated from ab initio calculations. The proposed mechanism for the carbonylsulfenyl chlorides includes two reaction pathways: one involves interaction with the S−Cl bond to give HCl; the second involves an RC(O)SCl·H adduct that subsequently gives RH and OCS (+Cl). The 〈Ev(OCS)〉 values were 17.2, 14.6, and 8.4 kcal mol-1 from FC(O)SCl, CH3OC(O)SCl, and ClC(O)SCl, respectively. The fraction of the available energy released as HCl vibrational energy, 〈fV(HCl)〉, from reaction with the S−Cl bond was ∼0.3 for all three reactions. The reaction mechanism for H + (CH3)3COCl, which was employed as a reference reaction, is thought to be direct abstraction and 〈fV(HCl)〉 is 0.23.