Conformational analysis of biphenyls: an upside-down view

Henry Rzepa

doi:10.15200/winn.143118.81906

Abstract

© Rzepa This article is distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and redistribution in any medium, provided that the original author and source are credited. One of the (not a few) pleasures of working in a university is the occasional opportunity that arises to give a new lecture course to students. New is not quite the correct word, since the topic I have acquired is Conformational analysis. The original course at Imperial College was delivered by Derek Barton himself about 50 years ago (for articles written by him on the topic, see DOI 10.1126/science.169.3945.539 or the original 10.1039/QR9561000044), and so I have had an opportunity to see how the topic has evolved since then, and perhaps apply some quantitative quantum mechanical interpretations unavailable to Barton himself.

Highlights

The example I have chosen to focus on here is biphenyl, but modified with isoelectronic B/N substitution for carbon for a particular reason
Such close approaches are normally defined with reference to the so-called van der Waals radius of the element concerned. This radius is either 1.2Å or 1.1Å. An interpretation of this value is that the van der Waals attraction due to to dispersion or long range correlation effects reaches a maximum for two non-bonded hydrogen atoms at RZEPA The Winnower MAY 09 2015
Let me introduce the results of a calculation (wB97XD/6-31G(d,p), a DFT method selected because it treats the long range correlation effects with a specific correction)

Summary

Introduction

Conformational analysis of biphenyls: an upside-down view An interpretation of this value is that the van der Waals attraction due to to dispersion or long range correlation effects reaches a maximum for two non-bonded hydrogen atoms at RZEPA The Winnower MAY 09 2015 CONFORMATIONAL ANALYSIS OF BIPHENYLS: AN UPSIDE-DOWN VIEW : CHEMISTRY

Results

Conclusion