Indices of Transition State Symmetry in Proton-Transfer Reactions. Kinetic Isotope Effects and Brønested's Β in Base-Catalyzed Diazo-Coupling Reactions
Abstract
The applicability of kH/kD and of Bronsted's β as indices of transition state symmetry in proton-transfer reactions has been tested in a number of base-catalyzed electrophilic aromatic substitution reactions. The data obtained from measurements involving the coupling of the diazonium salts of m- and p-chloroanilings, p-nitroaniline, and 4-amino-3-hydroxy-benzenesulfonic acid with two naphthols and their deuterated analogs, catalyzed by 12 bases, provide ample evidence for doubting the validity of β as a measure of the degree of proton transfer at the transition state. Variations in the structure of the transition state, caused by changes in the pKa of the catalyzing base, are more readily reflected in kH/kD. The origin of the observed variation of isotope effects is discussed, and the validity of kH/kD as an index of transition state symmetry is questioned. © 1974, American Chemical Society. All rights reserved.
Recommended Citation
S. B. Hanna et al., "Indices of Transition State Symmetry in Proton-Transfer Reactions. Kinetic Isotope Effects and Brønested's Β in Base-Catalyzed Diazo-Coupling Reactions," Journal of the American Chemical Society, vol. 96, no. 23, pp. 7222 - 7228, American Chemical Society, Nov 1974.
The definitive version is available at https://doi.org/10.1021/ja00830a009
Department(s)
Chemistry
International Standard Serial Number (ISSN)
1520-5126; 0002-7863
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2026 American Chemical Society, All rights reserved.
Publication Date
01 Nov 1974
