Universität zu Köln

Mayer, Robert J. ORCID: 0000-0002-9864-7042, Breugst, Martin ORCID: 0000-0003-0950-8858, Hampel, Nathalie, Ofial, Armin R. and Mayr, Herbert ORCID: 0000-0003-0768-5199 (2019). Ambident Reactivity of Phenolate Anions Revisited: A Quantitative Approach to Phenolate Reactivities. J. Org. Chem., 84 (14). S. 8837 - 8859. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6904

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Abstract

Prompted by the observation that the regioselectivities of phenolate reactions (C versus O attack) are opposite to the predictions by the principle of hard and soft acids and bases, we performed a comprehensive experimental and computational investigation of phenolate reactivities. Rate and equilibrium constants for the reactions of various phenolate ions with benzhydrylium ions (Aryl(2)CH(+)) and structurally related quinone methides have been determined photometrically in polar aprotic solvents. Quantum chemical calculations at the SMD(MeCN)/M06-2X/6-31+G(d,p) level confirmed that O attack is generally favored under kinetically controlled conditions, whereas C attack is favored under thermodynamically controlled conditions. Exceptions are diffusion limited reactions with strong electrophiles, which give mixtures of products arising from O and C attack, as well as reactions with metal alkoxides in nonpolar solvents, where oxygen attack is blocked by strong ion pairing. The Lewis basicity (LB) and nucleophilicity (N, s(N)) parameters of phenolates determined in this work can be used to predict whether their reactions with electrophiles are kinetically or thermodynamically controlled and whether the rates are activation-or diffusion-limited. Comparison of the measured rate constants for the reactions of phenolates with carbocations with the Gibbs energies for single electron transfer manifests that these reactions proceed via polar mechanisms.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Mayer, Robert J. UNSPECIFIED orcid.org/0000-0002-9864-7042 UNSPECIFIED Breugst, Martin UNSPECIFIED orcid.org/0000-0003-0950-8858 UNSPECIFIED Hampel, Nathalie UNSPECIFIED UNSPECIFIED UNSPECIFIED Ofial, Armin R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mayr, Herbert UNSPECIFIED orcid.org/0000-0003-0768-5199 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-134939
DOI:	10.1021/acs.joc.9b01485
Journal or Publication Title:	J. Org. Chem.
Volume:	84
Number:	14
Page Range:	S. 8837 - 8859
Date:	2019
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-6904
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MEISENHEIMER COMPLEX-FORMATION; PHENOXIDE ION; SOFT ACIDS; NUCLEOPHILIC-ADDITION; ARYLOXIDE IONS; BASES HSAB; ALKYLATION; CARBON; KINETICS; OXYGEN Multiple languages Chemistry, Organic Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13493