Twist angles and bond lengths in three twisted push–pull ethylenes. Interplay between steric and electronic effects
Autor: | Agha Zul-Qarnain Khan, Fen-Ling Liao, Jan Sandström, Sue-Lein Wang |
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Rok vydání: | 1994 |
Předmět: | |
Zdroj: | J. Chem. Soc., Perkin Trans. 2. :1569-1573 |
ISSN: | 1364-5471 0300-9580 |
DOI: | 10.1039/p29940001569 |
Popis: | Crystal structures of 1,3-dibenzyl-2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hexahydropyrimidine and two of its sulfur derivatives have been determined by X-ray crystallography. The molecules are formally push–pull ethylenes, but due to strong steric interaction between the donor and acceptor parts they are twisted by 72° to 85° about the formal double bond, and they are best described as zwitterions with an amidinium ion and a carbanion part. The degree of twisting is discussed in terms of steric and electronic effects, and electron distributions from AM1 and CNDO/S calculations are described. |
Databáze: | OpenAIRE |
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