OXIDATION OF CS2 BY REACTION WITH OH .1. EQUILIBRIUM-CONSTANT FOR THE REACTION OH+CS2 REVERSIBLE CS2OH AND THE KINETICS OF THE CS2OH+O2 REACTION

The reaction of OH with CS2 was studied in He (50 Torr), N2 (9-40 Torr), and SF6 (30-60 Torr) over the temperature range 249-318 K by using pulsed laser photolysis to generate OH and pulsed-laser-induced fluorescence to detect OH. The rapid approach of [OH] to equilibrium was observed at each temperature, indicating reversible formation of a CS2OH adduct. Analysis of the [OH] temporal profiles provided the rate coefficients for the forward and reverse components of the reaction OH + CS2 + M ⇄ CS2OH + M and, hence, the equilibrium constant. The temperature dependence of the equilibrium constant yielded the heat of reaction, ΔH°298 = -10.9 ± 1.0 kcal mol-1 and the entropy change for the reaction, ΔS°298 = -24.0 ± 4.4 cal K-1 mol-1. No evidence could be found for a direct non-adduct-forming channel for the OH + CS2 reaction leading to k(OH + CS2 → products) ≤ 2 × 10-15 cm3 molecule-1 s-1. An enhancement by O2 of the OH loss rate in CS2 was observed, confirming the occurrence of a reaction between CS2OH and O2. Analysis of the [OH] temporal profiles gave a rate coefficient for the CS2OH + O2 reaction of (2.6 ± 1.0) × 10-14 cm3 molecule-1 s-1 which was independent of temperature from 249 to 299 K. © 1990 American Chemical Society.