Professor Herbert Mayr

Date & time

11am–12pm 20 September 2012

Location

RSC Lecture Theatre

Speakers

Professor Herbert Mayr

Contacts

 Professor Martin Banwell
 6125 8202

Thursday 20th September: Professor Herbert Mayr, Ludwigs-Maximilians-Universität München, will present a Research Lecture entitled Mythology in Organic Chemistry. RSC Lecture Theatre, 11AM.
Abstract
Several concepts in organic chemistry persist, though their inconsistency has repeatedly been demonstrated in the past. This presentation will report on recent developments in the author’s laboratory on three different topics
1)   Reactivity selectivity principle:1 In activation-controlled reactions, selectivity may decrease, increase, or remain constant as reactivity increases. Only when the diffusion limit is approached, is an increase of reactivity generally associated with a decrease of selectivity.
2)   Kornblum’s rule and Salem-Klopman concept of charge and orbital controlled reactions:2 The ambident reactivities of the prototype nucleophiles, thiocyanate, cyanide, nitrite, cyanate, nitronate, phenylsulfinate, amide, and pyridone anions, cannot be described by these rules. Changes from kinetic to thermodynamic control, and from activation to diffusion limited reactivity has to be considered when interpreting ambident reactivities. A novel approach to ambident reactivity based on Marcus theory will be presented.
3)   α-Effect: According to IUPAC,3 the α-effect describes a positive deviation of an α-nucleophile (a nucleophile bearing an unshared pair of electrons on an atom adjacent to the nucleophilic site) from a Brønsted-type plot of lg k vs. pKa constructed for a series of related normal nucleophiles. More generally, it is the influence of the atom bearing a lone pair of electrons on the reactivity at the adjacent site. Systematic kinetic investigations of the nucleophilic reactivities of a series of hydrazines in various solvents do not give evidence for unusual reactivities, i. e., reactivities which differ from those of ordinary alkylamines.4 The concept of the α-effect should, therefore, be revised.
(1)   H. Mayr, A. R. Ofial, Angew. Chem. Int. Ed. Engl. 2006, 45, 1844-1854.
(2)   H. Mayr, M. Breugst, A. R. Ofial, Angew. Chem. Int. Ed. 2011, 50, 6470-6505.
(3)   P. Müller, Glossary of Terms used in Physical Organic Chemistry, Pure Appl. Chem. 1994, 66, 1077-1184.
(4)  T. A. Nigst, J. Ammer, H. Mayr, Angew. Chem. Int. Ed. 2012, 51, 1353-1356.

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