Files in this item
Proton transfer reactions of N-aryl triazolium salts : unusual ortho-substituent effects
Item metadata
dc.contributor.author | Tucker, David E. | |
dc.contributor.author | Quinn, Peter | |
dc.contributor.author | Massey, Richard S. | |
dc.contributor.author | Collett, Christopher John | |
dc.contributor.author | Jasiewicz, David J. | |
dc.contributor.author | Bramley, Christopher R. | |
dc.contributor.author | Smith, Andrew David | |
dc.contributor.author | O’Donoghue, AnnMarie C. | |
dc.date.accessioned | 2015-12-07T00:11:15Z | |
dc.date.available | 2015-12-07T00:11:15Z | |
dc.date.issued | 2015-02 | |
dc.identifier.citation | Tucker , D E , Quinn , P , Massey , R S , Collett , C J , Jasiewicz , D J , Bramley , C R , Smith , A D & O’Donoghue , A C 2015 , ' Proton transfer reactions of N-aryl triazolium salts : unusual ortho -substituent effects ' , Journal of Physical Organic Chemistry , vol. 28 , no. 2 , pp. 108-115 . https://doi.org/10.1002/poc.3399 | en |
dc.identifier.issn | 0894-3230 | |
dc.identifier.other | PURE: 159434357 | |
dc.identifier.other | PURE UUID: bae05965-6228-4652-9821-dcf88d2aa2c2 | |
dc.identifier.other | WOS: 000349079600008 | |
dc.identifier.other | Scopus: 85027936558 | |
dc.identifier.other | ORCID: /0000-0002-2104-7313/work/36567503 | |
dc.identifier.uri | https://hdl.handle.net/10023/7893 | |
dc.description | The authors thank the EPSRC (D. E. T., R. S. and C. J. C.) and Durham University (P. Q., D. J. J. and C. R. B.) for funding of this project. | en |
dc.description.abstract | Previous studies of the C(3)-hydrogen/deuterium exchange reactions of the triazolium ion conjugate acids of triazolyl N-heterocyclic carbenes revealed a change of mechanism under acidic conditions with N1-protonation to a dicationic salt. Interestingly, the data suggested an increase in pKaN1 in the presence of a N-pentafluorophenyl substituent relative to other N-aryl substituents with hydrogens or methyl substituents rather than fluorines at the ortho-positions. To probe the presence of an apparent donor effect of a N-pentafluorophenyl substituent, which differs from the more common electron withdrawing effect of this group, we have studied the analogous deuterium exchange reactions of four triazolium salts with heteroatoms or heteroatom substituents in the 2-position and/or 6-position of the N-aryl ring. These include triazolium salts with N-2,4,6-tribromophenyl 11, N-2,6-dichlorophenyl 12, N-2-pyridyl 13 and N-2-pyrimidinyl 14 substituents. The log kex – pD profiles for 11, 12 and 14 were found to show similar trends at lower pDs as for the previously studied N-pentafluorophenyl triazolium salt, hence supporting the presence an apparent donor effect on pKaN1. Surprisingly, the log kex – pD profile for N-pyridyl salt 13 uniquely showed acid catalysis at lower pDs. We propose herein that this data is best explained by invoking an intramolecular general base role for the N-(2-pyridyl) substituent in conjunction with N1-protonation on the triazolium ring. Finally, the second order rate constants for deuteroxide ion catalysed C(3)-H/D exchange (kDO, M−1 s−1), which could be obtained from data at pDs >1.5, were used to provide estimates of C(3)-carbon acid pKaC3 values for the four triazolium salts 11, 12, 13, 14. | |
dc.language.iso | eng | |
dc.relation.ispartof | Journal of Physical Organic Chemistry | en |
dc.rights | Copyright © 2014 John Wiley & Sons, Ltd. This is the accepted version of the following article: Tucker, D. E., Quinn, P., Massey, R. S., Collett, C. J., Jasiewicz, D. J., Bramley, C. R., Smith, A. D., & O’Donoghue, A. C. (2015). Proton Transfer Reactions of N-Aryl Triazolium Salts: Unusual Ortho-Substituent Effects. Journal of Physical Organic Chemistry, which has been published in final form at http://dx.doi.org/10.1002/poc.3399 | en |
dc.subject | Deuterium exchange | en |
dc.subject | N-heterocyclic carbene | en |
dc.subject | Organic catalysis | en |
dc.subject | Proton transfer | en |
dc.subject | Triazolium | en |
dc.subject | QD Chemistry | en |
dc.subject | NDAS | en |
dc.subject.lcc | QD | en |
dc.title | Proton transfer reactions of N-aryl triazolium salts : unusual ortho-substituent effects | en |
dc.type | Journal article | en |
dc.description.version | Postprint | en |
dc.contributor.institution | University of St Andrews. School of Chemistry | en |
dc.contributor.institution | University of St Andrews. Biomedical Sciences Research Complex | en |
dc.contributor.institution | University of St Andrews. EaSTCHEM | en |
dc.identifier.doi | https://doi.org/10.1002/poc.3399 | |
dc.description.status | Peer reviewed | en |
dc.date.embargoedUntil | 2015-12-07 | |
dc.identifier.url | http://onlinelibrary.wiley.com/doi/10.1002/poc.3399/suppinfo | en |
This item appears in the following Collection(s)
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.