Document Type

Article

Publication Date

2-2008

Publication Source

Journal of Molecular Structure: THEOCHEM

Abstract

The current report presents the first theoretical study of the restricted CN bond rotation in carbamoyl chlorides. Several N-benzyl-N-methylcarbamoyl chlorides were investigated, with varying pattern of substitution in the aromatic ring. Optimizations and frequency calculations were conducted employing DFT at the B3LYP/6-31+G(d) level of theory. Each of the studied structures exhibits a pair of rotamers (s-Z and s-E), generated upon rotation around the C(O)N bond. The s-E isomer is the global minimum in every case, but the preference for it is usually less than 1 kcal/mol. Two possible transition state structures were identified for the rotamer interconversion: TSsyn and TSanti, in close analogy to other related compounds, such as amides and carbamates. In contrast to the two latter types, however, the preferred transition state in the case of carbamoyl chlorides is TSsyn, which we attribute to a stabilizing gauche effect. The optimized minima structures of the studied carbamoyl chlorides were subjected to GIAOB3LYP/6-311+G(2d,p) calculations, and the resultant isotropic shifts were found to be in excellent agreement with available experimental values. This has allowed us to provide unambiguous NMR signal assignments for the s-E and s-Z isomers of the studied compounds.

Inclusive pages

105-110

ISBN/ISSN

0022-2860

Document Version

Postprint

Comments

The document available for download is the authors' accepted manuscript, posted here in compliance with the publisher's policy on self-archiving.

Some differences may exist between this version and the publisher's version; as such, researchers wishing to quote directly from it are advised to consult the version of record, available at many libraries or from the publisher.

Permission documentation is on file.

Publisher

Elsevier

Volume

850

Issue

1-3

Peer Reviewed

yes