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

Infrared chemiluminescence from a room-temperature flow reactor was used to study the reactions of H atoms with (CH 3 ) 3 COCl, ClC(O)SCl, FC(O)SCl, and CH 3 OC(O)SCl. Infrared emission spectra were recorded from the HCl, HF, and OCS products. The anharmonic shifts from bands involving ν 1, ν 2, and ν 3 excitation are too small to obtain information about bending vs stretch excitation of OCS from the Δ v 3 = −1 spectra; however, a computer simulation method was developed to analyze the Δ v 3 = −1 transition to assign the average total vibrational energy of OCS, 〈 E v (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 〈 E v (OCS)〉 values were 17.2, 14.6, and 8.4 kcal mol -1 from FC(O)SCl, CH 3 OC(O)SCl, and ClC(O)SCl, respectively. The fraction of the available energy released as HCl vibrational energy, 〈 f V (HCl)〉, from reaction with the S−Cl bond was ∼0.3 for all three reactions. The reaction mechanism for H + (CH 3 ) 3 COCl, which was employed as a reference reaction, is thought to be direct abstraction and 〈 f V (HCl)〉 is 0.23.