The Relative Electron Acceptor Abilities of the NO2, NO and CHO Groups and Their Application to the NBO-TS Torquoselectivity

13 October 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


As against the long held notion in the prediction of torquoselectivity, the relative p- and s-acceptor abilities of NO2, NO and CHO are demonstrated to decrease in the order NO2 > NO > CHO from a combination of different computational parameters.

In systems such as 3-NO2/NO/CHO-cyclobutenes, sC3C4→p*NO and sC3C4→p*CO interactions in the transition states leading to inward or outward opening of the ring are significant. These interactions during the inward opening are much larger than in the outward opening of the three instances discussed herein.


pi-acceptor ability
sigma-acceptor ability
sigma-pi* interaction

Supplementary materials



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