ISSN:
0009-2940
Keywords:
N-Benzylpyridinium bromide / MO calculations versus crystal structure determinations / Conformational analysis
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Conformational Analysis of N-Benzylpyridinium Bromide: A Comparison of Crystal Structure Data with Results of Semiempirical Calculations (MINDO/3, MNDO, AM 1, and PM3)The conformation of the title compound 1b is investigated by X-ray analysis and semiempirical MO methods (MINDO/3, MNDO, AM1, PM3). For the calculation of bond lengths and bond angles, AM1 and MINDO/3 are superior. Without complete calculation of the hypersurfaces of the variable D1, D2 and the relative energy (e. g. Figure 2), AM1 and MNDO can lead to false interpretations. Cuts through these surfaces (Figure 1) are calculated within moderate CPU time, Normally, these cuts are sufficient to characterize the conformational situation. The electronic influence of the phenyl group on the N1-C7 bond length of N-alkylpyridinium salts and on the dissociation energy ΔHz (eg. 2) is estimated. The comparison of the data of 1a and 1b reveals that this group causes an elongation of this bond by 2 pm and a decrease of the dissociation energy by 200 kJ/mol.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901230217
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