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A theoretical study of (old and new) non‐classical carbocations derived from cyclic saturated hydrocarbons
Author(s) -
Alkorta Ibon,
Abboud José Luis M.,
Quintanilla Esther,
Dávalos Juan Z.
Publication year - 2003
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.630
Subject(s) - carbocation , chemistry , natural bond orbital , computational chemistry , ab initio , charge density , moiety , atomic orbital , molecular orbital , electron , density functional theory , molecule , stereochemistry , organic chemistry , quantum mechanics , physics
Abstract Nine non‐classical carbocations derived from cyclic saturated hydrocarbons were studied by means of ab initio calculation, MP2/6–311G**. The geometry, energetics, orbital interactions within the Natural Bond Orbital formalism, electron density and chemical shieldings were obtained and analyzed. In all cases a similar geometrical distribution (‘non‐classical moiety,’ NCM) was obtained with the carbon atoms located in a triangle with two of their sides of 1.84 Å and the third of 1.40 Å. The energetic stability of the carbocations was rationalized on the basis of the strain in the rings involved. The NBO analysis shows that the charge is largely distributed over the three centers and also the existence of a two‐electron, three‐center orbital with similar contribution of the three atoms. Electron density maps were obtained and analyzed. In all cases, the chemical shieldings of the CH 2 group of the NCM are in the region of saturated hydrocarbons whereas those for the CH group are similar to those found in double‐bonded systems. Copyright © 2003 John Wiley & Sons, Ltd.