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Kinetics, Thermodynamics, and Mechanism of the Formation of Benzaldehyde-sulfur(IV) Adducts

Olson, Terese M. and Boyce, Scott D. and Hoffmann, Michael R. (1986) Kinetics, Thermodynamics, and Mechanism of the Formation of Benzaldehyde-sulfur(IV) Adducts. Journal of Physical Chemistry, 90 (11). pp. 2482-2488. ISSN 0022-3654. doi:10.1021/j100402a043.

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The kinetics and mechanism of the formation of α-hydroxyphenylmethanesulfonate (HPMS) by the addition of bisulfite to benzaldehyde were studied at low pH. A three-term rate law was observed as d[HPMS]/dt = (k_1α -2 + (k_2 + k_3K_H^- {H^+})α_1)[S(IV)]_t[C_6H_5CHO] where α_1 = [HSO_3^-]/[S(IV)], α_2 = [SO_3^(2-)/[S(IV)], and K_H is the proton association constant of benzaldehyde. The Rate-limiting steps of each term appeared to be the nucleophilic attack of HSO_3^- on the carbonyl carbon of benzaldehyde, the attack of HSO_3^- on the carbonyl carbon, and the attack by HSO_3^- on the protonated carbon of the carbocation, C_6H_5C^+H(OH), respectively. Over the pH range of most natural systems, only the k_1 and k_2 steps contribute to adduct formation while the k_3 term becomes important for pH < 1. At 25 ºC and µ = 1.0 M, the intrinsic rate constants were determined to be k_1 = (2.15 ± 0.09) X 10^4 M^(-1)s^(-1), k_2 = (0.71 ± 0.03) M^(-1) s^(-1), k_3 ≅ 2.5 x 10^7 M^(-1) s^(-1). Para-substitution on the benzaldehyde ring resulted in a slight increase in reactivity for p-NO_2- and p-Cl-, and a decrease for p-OH-, p-OCH_3-, and p-CH_3-C_6H_5CHO. The equilibrium association constant, K = [C_6H_5CH(OH)SO_3^-]/[HSO_3-] [C_6H_5CHO], at 25 ºC was determined to be 4.8 (±0.8) x 10^3 at µ = 0.1 M and 0.98 (±0.11) x 10^3 M^(-1) at µ = 1.0 M. ΔHº and ΔSº were determined to be -64.6 kJ mol^(1-) and -146 J mol^(-1) deg^(-1), respectively.

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Hoffmann, Michael R.0000-0001-6495-1946
Alternate Title:Kinetics, thermodynamics, and mechanism of the formation of benzaldehyde-s(IV) adducts
Additional Information:© 1986 American Chemical Society. Received: October 11, 1985; In Final Form: January 8, 1986. Publication Date: May 1986. We gratefully acknowledge the Electric Power Research Institute (RP1630-47) and the Environmental Protection Agency (R8 11496-01-1) for providing financial support for this research. We also thank Drs. Detlef W. Bahnemann, Eric A. Betterton, and the reviewers for their helpful insight.
Funding AgencyGrant Number
Electric Power Research Institute (EPRI)RP 1630-47
Environmental Protection Agency (EPA)R811496-01-1
Issue or Number:11
Record Number:CaltechAUTHORS:20150818-100953306
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Official Citation:Kinetics, thermodynamics, and mechanism of the formation of benzaldehyde-sulfur(IV) adducts Terese M. Olson, Scott D. Boyce, and Michael R. Hoffmann The Journal of Physical Chemistry 1986 90 (11), 2482-2488 DOI: 10.1021/j100402a043
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59686
Deposited By: Ruth Sustaita
Deposited On:19 Aug 2015 15:57
Last Modified:10 Nov 2021 22:23

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