Reversible isomerization of methylcyclopentadienes directed by selective excitation of the methyl out-of-plane fourth overtone transition

Laser vibrational overtone excitation has been employed to study the reversible isomerization of 2-methylcyclopentadiene and 1-methylcyclopentadiene. Spectroscopy of the third through fifth overtones is reported for both isomers. The specific rate coefficients for the energies corresponding to the fourth overtone methyl out-of-plane CH stretch transitions have been derived and compared to those calculated from RRKM theory for the forward and reverse reactions. It is demonstrated that selective overtone excitation of one isomer in the 50:50 mixture enriches the mixture with another isomer.