ISSN:
0894-3230
Keywords:
cycloheptatriene
;
silacycloheptatriene
;
ring inversion
;
aromaticity
;
ab initio calculation
;
nucleus-independent chemical shift
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Nucleus-independent chemical shifts (NICS) of boat and planar structure of silepins (1) and cycloheptatriene (2) were calculated at the HF/6-31+G* level for the Becke3LYP/6-31G* optimized geometries in order to investigate the correlation between the inversion barrier and aromatic nature in the boat and planar forms of 1 and 2. The NICS of unsubstituted silepin 1a indicated that there is almost no stabilization in the boat form (NICS, -0.5) and that the planar form (NICS, 3.5) is relatively destabilized in comparison with the boat form. On the other hand, the NICS of 2 showed that there is considerable homoconjugative stabilization in the boat form (NICS, -4.2) and destabilization in the planar form (NICS, 8.2). In addition to the geometrical effects resulting from angle strain, these electronic effects are considered to affect the energy barriers for ring inversion, which have been calculated to be 0.9 kcal mol-1 for 1a and 5.2 kcal mol-1 for 2. © 1998 John Wiley & Sons, Ltd.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
