Reactions of the nitrate radical with a series of reduced organic sulphur compounds in air

Abstract

A 480 L evacuable reaction chamber, equipped with FT-IR spectroscopy on-line and ion chromatography off-line, has been used to study the gas phase reaction between the nitrate radical, NOa, and the reduced organic sulphur compounds CH~CHZSH, ( C H~C H~Z S , (CH~CHZ)ZSZ, and CH&H2SCH3 in air. The products CHaCHZS03H, SOZ, HzS04, CH3CH0, and CH~CHZONOZ were identified and quantified in the reactions of the first three compounds, CH~CHZSH, (CH3CH2),S, and (CH~CHZ)&. The reaction products were CH&HZS03H, CHaSOaH, SOZ, HzS04, CH3CH0, and CH20 in the reaction of CH3CH2SCH3. On the basis ofidentified reaction products and intermediates observed in the infrared spectra, mechanisms are proposed for the reactions between the NO3 radical and the four reduced organic sulphur compounds. The results of this study, together with those from previous experiments performed in this laboratory on CH3SCH3, CHaSH, and CH3SSCH3 lead to the conclusion that all these species, in the reaction with the NO3 radical, follow a similar degradation mechanism producing SO?, H2SO4, R -S03H, R-CHO, and R-CHZONO~, as the main reaction products. The inital step of the reaction of NO3 with R-S-R and R-S-H type (R=CH3, CHZCH3) reduced organic sulphur compounds was found to be H-atom abstraction, probably after the formation of an initial adduct.

Kinetic and mechanistic study of Cl reactions with aliphatic thiols. Temperature dependence

“…Several authors have reported the reactions of aliphatic thiols with OH 7,8 and NO 3 . 2,9 For the reactions with OH, the obtained values for the rate constants of CH 3 CH 2 SH, CH 3 CH 2 CH 2 SH and (CH 3 ) 2 CHSH at 298 K are 8 4.5 Â 10 À11 , 5.3 Â 10 À11 and 3.9 Â 10 À11 cm 3molecule À1 s À1 , respectively. Both studies 7,8 were carried out under high pressure conditions (30-100 Torr and 1 atm, respectively) and the authors conclude that the dominant reaction pathway is addition to the sulfur atom.…”

“…Natural emissions account for about 25% of total sulfur emission 1 and reduced organic sulfur compounds have been estimated to account for approximately 25% of the total global gaseous sulfur budget. 2 These reduced organic sulfur compounds are mainly emitted from the sea surface and by biological activity. A number of these compounds have been detected in the atmosphere including COS, CS 2 , H 2 S, CH 3 SH and CH 3 SCH 3 (DMS).…”

Post-discharge treatment of air effluents polluted by butyl-mercaptan: the role of nitrate radical

“…Among the long-life species produced by the atmospheric air discharge, only the nitrate radical NO 3 can react with mercaptans. The kinetic constants of the secondorder reactions between NO 3 and ethyl-mercaptan C 2 H 5 -SH and methyl-mercaptan CH 3 -SH are respectively 1.2×10 -12 [10] and 9.2×10 -13 [11] cm 3 .molecule -1 .s -1 at 298 K and the reaction mechanism involves hydrogen abstraction from the -SH bond by the nitrate radical with formation of a radical R-S° and nitric acid HNO 3 [12]:…”

“…The radical R-S° can then undergo multiple reactions due to reactions with molecular oxygen and/or nitrogen oxides. Basing on the mechanism proposed by Jensen et al [12], the scheme presented in figure 6 can be suggested for the destruction of mercaptans: Figure 6. Possible mechanisms for the oxidation of C 4 H 9 SH initiated by NO 3…”