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Bond Angles in Lactones and Lactams
Author(s) -
NørskovLauritsen Leif,
Bürgi HansBeat,
Hofmann Peter,
Schmidt Helmut R.
Publication year - 1985
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19850680110
Subject(s) - chemistry , mindo , mndo , anomeric effect , lone pair , antibonding molecular orbital , crystallography , group (periodic table) , ring (chemistry) , computational chemistry , molecular orbital , molecular geometry , stereochemistry , molecule , atomic orbital , anomer , organic chemistry , physics , quantum mechanics , electron
The carbonyl group in lactones and, to a lesser extent, in lactams tends to show a CCO angle that is larger than the OCO or NCO angle, the difference increasing in magnitude as the ring size decreases. The observed trend provides information on ratios of force constants characterising the flexibility of the s‐ cis ‐ester group and may be interpreted in terms of incipient chemical reaction to − O(CH 2 ) n CO + . Molecular orbital calculations (MINDO/3, MNDO, EH) for model compounds provide an electronic interpretation of this angle difference in terms of an anomeric interaction between the p‐type lone pair on the carbonyl O‐atom and the antibonding C‐O or C‐N orbital.