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Chem Commun (Camb). 2013 Sep 25;49(74):8166-8. doi: 10.1039/c3cc44573a.

An n→π* interaction reduces the electrophilicity of the acceptor carbonyl group.

Author information

1
Graduate Program in Biophysics, University of Wisconsin-Madison, 1525 Linden Drive, Madison, WI 53706-1534, USA.

Abstract

Carbonyl-carbonyl (C=O···C'=O') interactions are ubiquitous in both small and large molecular systems. This interaction involves delocalization of a lone pair (n) of a donor oxygen into the antibonding orbital (π*) of an acceptor carbonyl group. Analyses of high-resolution protein structures suggest that these carbonyl-carbonyl interactions prefer to occur in pairs, that is, one donor per acceptor. Here, the reluctance of the acceptor carbonyl group (C'=O') to engage in more than one n→π* electron delocalization is probed using imidazolidine-based model systems with one acceptor carbonyl group and two equivalent donor carbonyl groups. The data indicate that the electrophilicity of the acceptor carbonyl group is reduced when it engages in n→π* electron delocalization. This diminished electrophilicity discourages a second n→π* interaction with the acceptor carbonyl group.

PMID:
23928794
PMCID:
PMC3840071
DOI:
10.1039/c3cc44573a
[Indexed for MEDLINE]
Free PMC Article

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