ISSN:
0192-8651
Keywords:
Computational Chemistry and Molecular Modeling
;
Biochemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Computer Science
Notes:
The molecular structure of the stretched form of n-nonane, as a typical long-chain hydrocarbon, was refined by geometrically unconstrained ab initio force relaxation on the 4-21G level. The C—C bonds and C—H bond distances in the interior of the hydrocarbon chain are found to be longer (by about 0.001 Å and 0.002 Å, respectively) than those near the end of the chain. Similarly, interior C—C—C bond angles are 0.4° larger than the terminal angles. The variation of structural parameters with distance from the molecular ends levels off after the second carbon atom, and the geometry of methylene is practically constant from C3 on. However, if one end of the system is perturbed by moving the inplane methyl hydrogen away from equilibrium, the resulting destabilizing electronic effects are transmitted through the C—C bond distance chain in such a way that significant perturbations are still experienced at C5. Molecular mechanics (MM2) gives a structure in which the small changes in bond lengths and angles with chain location are well reproduced.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcc.540030220
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