ISSN:
0948-5023
Keywords:
Keywords Molecular mechanics
;
MM2
;
Parameterisation
;
Carbonyl group
;
Heterocyclic molecules
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract A new type of carbon atom has been included in the MM2 force field when it is part of a carbonyl group cross-conjugated in a heterocyclic molecule. This carbon atom is fully included in the π system calculation. New stretching parameters for the C=O bond have been estimated by a statistical process from X-ray molecular structures recorded in the Cambridge Structural Database System. The proposed parameters have been found appropriate for compounds in which the atoms adjacent to the carbonyl are a carbon and a heteroatom i.e. mainly for the α-pyrone ring and the conjugated "lactams". They are inappropriate for carbonates and oxazo-ones but should be valid for quinones provided that they are not involved in a charge transfer complex. The mean unsigned deviation for 111 bond lengths (89 cyclic molecules) is 0.01Å but the maximum deviation can reach ± 0.03Å. Part of the observed dispersion could be the result of the variation of the effective dielectric constant D from one crystal to another.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s008940050098
