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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 . http://resolver.caltech.edu/CaltechAUTHORS:20150818-100953306

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Abstract

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.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/j100402a043DOIArticle
http://pubs.acs.org/doi/abs/10.1021/j100402a043PublisherArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0002-0432-6564
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.
Funders:
Funding AgencyGrant Number
Electric Power Research Institute (EPRI)RP 1630-47
Environmental Protection Agency (EPA)R811496-01-1
Record Number:CaltechAUTHORS:20150818-100953306
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150818-100953306
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
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:19 Aug 2015 15:57
Last Modified:19 Aug 2015 15:57

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