Abstract
Biphenyl is a prototype molecule, the study of which is important for a proper understanding of stereo-electronic effects. In the gas phase it has an equilibrium central torsion angle of ~ 45° and shows both a planar (0°) and a perpendicular (90°) torsional energy barrier. The latter is analysed for the first time. We use the newly proposed REG method, which is an exhaustive procedure that automatically ranks atomic energy contributions according to their importance in explaining the energy profile of a total system. Here, the REG method operates on energy contributions computed by the interacting quantum atoms method. This method is minimal in architecture and provides a crisp picture of well-defined and well-separated electrostatic, steric and exchange (covalent) energies at atomistic level. It is shown that the bond critical point occurring between the ortho-hydrogens in the planar geometry has been wrongly interpreted as a sign of repulsive interaction. A convenient metaphor of analysing football matches is introduced to clarify the role of a REG analysis.
Highlights
Quantum chemistry has developed into a powerful first principles science, able to make predictions regarding the energy and geometry of molecular systems, independent of experiment
3.1 relative energy gradient (REG) analysis: extracting chemical insight allowing for the three different energy types
The REG analysis is the key contribution of the current article to the literature on biphenyl rotations barrier, which is why we report it first
Summary
Quantum chemistry has developed into a powerful first principles science, able to make predictions regarding the energy and geometry of molecular systems, independent of experiment. Biphenyl is a prototype molecule, the study of which is important for a proper understanding of stereo-electronic effects This simple molecule is of significant interest as a molecular core for many current compounds currently under proposal for clinical trials [1]. This is due to its ability to stereo-control the formation of a drug according to substituent groups and their position in the phenyl ring. It should be noted that a partitioned energy is assigned to the foreground subset if it has a REG magnitude greater than the cut-off in any barrier.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
