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Facial Selectivity of the ( R )‐1,3‐Dimethyl‐1‐Cyclohexyl Cation in the Gas Phase
Author(s) -
Filippi Antonello
Publication year - 2003
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200304859
Subject(s) - selectivity , chemistry , carbocation , adduct , density functional theory , ionic bonding , ion , phase (matter) , computational chemistry , non covalent interactions , radiolysis , molecule , photochemistry , organic chemistry , aqueous solution , catalysis , hydrogen bond
The model reaction between the ( R )‐1,3‐dimethyl‐1‐cyclohexyl cation ( I ) and methanol has been investigated under gas‐phase radiolytic conditions (750 Torr; 25–120 °C) with the aim of evaluating the intrinsic factors that govern the facial selectivity of biased carbocations. The peculiarity of the experimental approach allows the formation of different CH 3 18 OH ⋅I ionic adducts. Subsequent conversion of these adducts to give the corresponding E / Z covalent products follows different reaction coordinates, which are characterized by their own activation parameters. On the grounds of density functional theory (DFT) results, several [CH 3 OH ⋅I ] structures have been located on the relevant potential‐energy surface (PES). The experimental results point to a gas‐phase facial selectivity, which is mainly governed by entropic factors that arise as a result of the occurrence of different noncovalent ion–molecule “facial adducts” (FA). The formation of FAs may also play an important role in both the reaction dynamics and the positional selectivity. The present results cannot be interpreted by any of the models based on solution‐phase experiments.