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Published November 1988 | public
Journal Article

Kinetics of the formation of hydroxyacetaldehyde-sulfur(IV) adducts at low pH

Abstract

The kinetics of the addition of hydroxyacetaldehyde and S(1V) was studied spectrophotometrically over the pH range of 0.7-3.3. Formation rates of the adduct 1,2-dihydroxy-1-ethanesulfonate (DHES) were consistent with the following three-term rate exmession: d[DHES]/dt = (k_0{H^+}α_1/K_(a0) + (k_1α_1 + k_2α_2) C_2H_3O_2]t[S(IV)] where [C_2H_3O_2]_t = [CH_2(OH)CHO] + CH_2(OH)CH(OH)_2] [S-(IV)] = [H_2O•SO_2] + [HSO_3^-] + [SO_3^(2-)],[S(IV)], and α_2 = [SO_3^(2-)]/ [S(IV)], and K_(a0) is the acid dissociation constant for CH_2(OH)C^+HOH. The rate constant k_0 corresponds to a proton-catalyzed pathway in which bisulfite reacts with the carbocation CH_2(OH)C^+_-HOH. A value for the constant k_0/K_(a0) was determined as 5.4 (±2.0) M^(-2), s^(-1) (25 ºC, µ = 0.2 M). The intrinsic constants k_1 and k_2 are the respective rate constants for the reactions of HSO_3^- and SO_3^(2-) with unhydrated hydroxyacetaldehyde, where it was determined that k_1 = 1.74 (±0.16) M^(-1) s^(-1) and k_2 = 5.02 (±0.12) x 10^4 M^(-1) s^(-1). Because of the high intrinsic solubility of CH_2(OH)CHO, calculated DHES formation rates in fogwater and cloudwater are faster than the addition rate of formaldehyde and S(IV). DHES is shown to satisfy the criteria of a significant S(IV) reservoir in atmospheric droplets.

Additional Information

© 1988 American Chemical Society. Received for review February 9, 1988. Accepted April 26, 1988. We gratefully acknowledge the Electric Power Research Institute for Organic Acids and Buses; Chapman and Hall: London, (RP1630-47), the U.S. Environmental Protection Agency 1981. (R811496-01-1), and the U.S. Public Health Service (ES04635-01) for their financial support.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023