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Um IH, Lee JY, Kim HT, et al. Curved Hammett plot in alkaline hydrolysis of O-aryl thionobenzoates: change in rate-determining step versus ground-state stabilization. J Org Chem. 2004;69(7):2436-41doi: 10.1021/jo035854r.
Um, I. H., Lee, J. Y., Kim, H. T., & Bae, S. K. (2004). Curved Hammett plot in alkaline hydrolysis of O-aryl thionobenzoates: change in rate-determining step versus ground-state stabilization. The Journal of organic chemistry, 69(7), 2436-41. https://doi.org/10.1021/jo035854r
Um, Ik-Hwan, et al. "Curved Hammett plot in alkaline hydrolysis of O-aryl thionobenzoates: change in rate-determining step versus ground-state stabilization." The Journal of organic chemistry vol. 69,7 (2004): 2436-41. doi: https://doi.org/10.1021/jo035854r
Um IH, Lee JY, Kim HT, Bae SK. Curved Hammett plot in alkaline hydrolysis of O-aryl thionobenzoates: change in rate-determining step versus ground-state stabilization. J Org Chem. 2004 Apr 02;69(7):2436-41. doi: 10.1021/jo035854r. PMID: 15049643.
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J Org Chem. 2004 Apr 02;69(7):2436-41. doi: 10.1021/jo035854r.

Curved Hammett plot in alkaline hydrolysis of O-aryl thionobenzoates: change in rate-determining step versus ground-state stabilization.

The Journal of organic chemistry

Ik-Hwan Um, Ji-Youn Lee, Han-Tae Kim, Sun-Kun Bae

Affiliations

  1. Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea. [email protected]

PMID: 15049643 DOI: 10.1021/jo035854r

Abstract

Second-order rate constants have been measured for alkaline hydrolysis of O-aryl thionobenzoates (X-C(6)H(4)-CS-OC(6)H(4)-Y) in 80 mol % H(2)O-20 mol % DMSO at 25.0 +/- 0.1 degrees C. The Hammett plot for the reaction of O-4-nitrophenyl X-substituted thionobenzoates (X-C(6)H(4)-CS-OC(6)H(4)-NO(2), 1a-e) exhibits a downward curvature. However, a possible traditional explanation in terms of a change in the rate-determining step (RDS) has been considered but rejected. The proposed explanation involves stabilization of the ground-state (GS) through-resonance interaction between the electron-donating substituent X and the thionocarbonyl functionality on the basis of the linear Yukawa-Tsuno plot obtained for the same reaction. The Brønsted-type plot for the reaction of O-aryl thionobenzoates (C(6)H(5)-CS-OC(6)H(4)-Y, 2a-i) is linear but exhibits many scattered points with a small beta(lg) (-0.35). The Hammett plot for the same reaction shows rather poor correlation with sigma(-) constants but much better correlation with sigma(o) constants. The alkaline hydrolysis of O-aryl thionobenzoates (1a-e and 2a-i) has been proposed to proceed through an addition intermediate in which bond formation is the RDS.

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