Abstract book - Prof. Per Jensen, Ph.D. - Bergische Universität ...

Contributed Lectures, N4 225Spectroscopic Observation of Benzyl-type Radicals using a Techniqueof Corona Excited Supersonic ExpansionYoung Wook Yoon 1 , Sang Kuk Lee 21 Department of Chemistry, Pusan National University, Korea, yywook630@naver.com2 Department of Chemistry, Pusan National University, Korea, sklee@pusan.ac.krLee S.K.Yoon Y.W.The benzyl radical, a prototype of aromatic free radical, has been believed to be a keyintermediate in aromatic chain reactions and the subject of numerous spectroscopicworks. On the other hand, benzyl-type radicals, ring-substituted benzyl radicals havereceived less attention due to the difficulties associated with the identification of thespecies and possible rearrangement of substituents at the transition state.The dimethylbenzyl chlorides were employed as precursors to generate each isomericdimethylbenzyl radical, 1 from whose spectra we clearly confirmed the assignments ofeach species in the spectrum observed from polymethylbenzenes. From the analysis ofthe spectra, we identified the benzyl-type radicals formed in the corona discharge of theprecursor and determined the electronic energy and several vibrational modes in the D 0state to confirm the assignments of bi-substituted benzyl radicals by comparison with anab initio calculation. The origin band shows increased shift to red region due to thesynergic effect of two substituents into benzene ring. 2 The shift of the origin band of themost of the poly-substituted benzyl radicals is comparable to the summation of thecontribution of each substituent regardless of the nature of substituent. However, thebenzyl-type radicals with substituent at the 4-position always show much smaller shiftthan others, for which we tried to explain the shift of the origin band using a simplemolecular orbital theory. The new model describes well the shift of the origin band ofthe homo- and hetero-substituted benzyl-type radicals for CH 3 and F substituents.Cl* *ClCl******* *19500 20000 20500 21000 21500 22000Wavenumber (cm -1 )References[1] Y. W. Yoon, S. K. Lee, J. Chem. Phys. 135, 214305, 2011.[2] Y. W. Yoon, S. K. Lee, J. Chem. Phys. 136, 024309, 2012.