“Recharging” Group Electronegativities: Computational Chemistry as a Tool for Estimating Electronegativity

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 16 (2011) pp 164-167

“Recharging” Group Electronegativities: Computational Chemistry as a Tool for Estimating Electronegativity

Matthew D. Moran,^† John-Paul Jones,^‡ Alan A. Wilson,^† Sylvain Houle,^† G. K. Surya Prakash,^‡ George A. Olah,^‡ and Neil Vasdev^†,*

^†PET Centre, Centre for Addiction and Mental Health and Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada, M5T-1R8; neil.vasdev@utoronto.ca; ^‡Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, University Park, Los Angeles, CA, 90089-1661
Received January 23, 2011. Accepted May 16, 2011.

Published: 8 July 2011

Abstract. Group electronegativity (gEN) is a fundamental concept of chemistry, relating to acidity, chemical reactivity, activating groups, and protecting groups. Although several empirical and computational methods have been devised for determining gEN, there is no straightforward computational method available to determine these values. We here revisit the determination of gENs using partial charges (“recharging”), computed at a high level of theory using the natural charge of a group (proton, methyl, vinyl, phenyl) bound to the substituent of interest and correlating the values with Pauling electronegativities. The results were found to be in good agreement with previous experimental and computational results. The values also qualitatively reproduced expected electronegativity trends. Furthermore, this work provides the first attempt to compare literature values by scaling them to a single metric (Pauling electronegativities). The method employed is simple and convenient, and could prove to be useful to chemists for determining the gEN of a substituent of interest, or by chemical educators as an assignment or laboratory exercise in a computational chemistry course.

Key Words: Laboratories and Demonstrations; quantitative analysis; electrochemistry; household products

(*) Corresponding author. (E-mail: neil.vasdev@utoronto.ca)

Article in PDF format (214 KB) HTML format

Supporting Materials:

Computational details; graph of charges on methyl against Pauling electronegativities for H, F, Cl, Br, and I (Figure S1); a sample input file (Figure S2); a sample NBO output (Figure S3); step-by-step instructions for determining group electronegativities from natural charges; literature values scaled to Pauling electronegativities (Figures S4–9); a full table of the charges on the proton, methyl group, and phenyl group of RX and the corresponding electronegativities of X (Table S1) (174 KB)