Issue 25, 2018

A DFT/PCM-based methodology for predicting solvolytic reactivities of organic carbonates

Abstract

The possibility of employing quantum mechanical computations to predict solvolysis rates of benzhydryl aryl/alkyl (Ar/R) carbonates and to determine nucleofugalities of various Ar/R carbonate leaving groups in terms of Nf values is examined. Since unassisted SN1 transition states of neutral substrates cannot be optimized by using implicit solvation models, a model reaction that includes anchimerically assisted heterolysis of 2-oxyethyl Ar/R carbonates is utilized to determine the relative reactivities of both benzhydryl Ar/R carbonate substrates and Ar/R carbonate leaving groups. Very good linear correlations have been obtained between activation free energies of the model reaction, calculated by using the M06-2X method in conjunction with the IEFPCM solvation model, and activation free energies in the literature for solvolysis of the corresponding benzhydryl Ar/R carbonates in a given solvent. The slopes of close to unity demonstrate that calculated and measured relative reactivities of the Ar/R carbonate leaving groups are practically the same. Very good agreement between experiment and theory has enabled extending the nucleofugality (Nf) scale established by Mayr and co-workers (Acc. Chem. Res., 2010, 43, 1537–1549) with numerous new Ar/R carbonate leaving groups.

Graphical abstract: A DFT/PCM-based methodology for predicting solvolytic reactivities of organic carbonates

Supplementary files

Article information

Article type
Paper
Submitted
18 Apr 2018
Accepted
30 May 2018
First published
11 Jun 2018

Org. Biomol. Chem., 2018,16, 4665-4674

A DFT/PCM-based methodology for predicting solvolytic reactivities of organic carbonates

M. Matić and B. Denegri, Org. Biomol. Chem., 2018, 16, 4665 DOI: 10.1039/C8OB00917A

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