Selectively Weakened C-C ?-Bond in Cation Radicals of Linear and Branched Pentanes As Studied By Electron Spin Resonance

Article abstract of DOI:10.1021/j100196a026

Radical cations which have the fully extended structure (trans-trans conformation) but have lost the symmetry of the mother molecules were detected by electron spin resonance for n-pentane, 3-methylpentane, and 3,3-dimethylpentane in frozen matrices at 4 K.It was indicated, with the aid of an INDO calculation, that one of the two inner C-C bonds in the main chain is elongated and the unpaired electron tends to be confined in this bond.Selective bond elongation was also shown for the trans-gauche conformers of 3-methylpentane and 3,3-dimethylpentane cations.These facts suggest that selective elongation of a C-C bond is essential with alkane cations even if it is not Jahn-Teller active.This selective weakening of a skeletal bond should be related to the selectivity in the bond scission in alkane radiolysis.In addition, hole migration between the solute alkanes in the frozen matrices at 77 K was suggested from the radical conversion between the different conformers.