Proton Transfer Reactions of Triazol-3-ylidenes: Kinetic Acidities and Carbon Acid pKa Values for Twenty Triazolium Salts in Aqueous Solution

Massey, R.S.; Collett, C.J.; Lindsay, A.G.; Smith, A.D.; O'Donoghue, A.C.

doi:10.1021/ja308420c

Proton Transfer Reactions of Triazol-3-ylidenes: Kinetic Acidities and Carbon Acid pKa Values for Twenty Triazolium Salts in Aqueous Solution

Massey, R.S.; Collett, C.J.; Lindsay, A.G.; Smith, A.D.; O'Donoghue, A.C.

Authors

R.S. Massey

C.J. Collett

A.G. Lindsay

A.D. Smith

Professor Ann O'Donoghue annmarie.odonoghue@durham.ac.uk
Professor

Abstract

Second-order rate constants have been determined for deuteroxide ion-catalyzed exchange of the C(3)-proton for deuterium, kDO (M–1 s–1), of a series of 20 triazolium salts in aqueous solution at 25 °C and ionic strength I = 1.0 (KCl). Evidence is presented that the rate constant for the reverse protonation of the triazol-3-ylidenes by solvent water is close to that for dielectric relaxation of solvent (1011 s–1). These data enabled the calculation of carbon acid pKa values in the range 16.5–18.5 for the 20 triazolium salts. pD rate profiles for deuterium exchange of the triazolium salts reveal that protonation at nitrogen to give dicationic triazolium species occurs under acidic conditions, with estimates of pKaN1 = −0.2 to 0.5.

Citation

Massey, R., Collett, C., Lindsay, A., Smith, A., & O'Donoghue, A. (2012). Proton Transfer Reactions of Triazol-3-ylidenes: Kinetic Acidities and Carbon Acid pKa Values for Twenty Triazolium Salts in Aqueous Solution. Journal of the American Chemical Society, 134(50), 20421-20432. https://doi.org/10.1021/ja308420c

Journal Article Type	Article
Publication Date	Dec 19, 2012
Deposit Date	May 16, 2013
Publicly Available Date	Feb 15, 2016
Journal	Journal of the American Chemical Society
Print ISSN	0002-7863
Electronic ISSN	1520-5126
Publisher	American Chemical Society
Peer Reviewed	Peer Reviewed
Volume	134
Issue	50
Pages	20421-20432
DOI	https://doi.org/10.1021/ja308420c

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Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/ja308420c.