Kinetic study of the gas-phase reaction c-C5H10 + I2 ⇄ c-C5H8 + 2HI the heat of formation of cyclopentyl radical

✍ Scribed by Shozo Furuyama; David M. Golden; Sidney W. Benson

• Publisher: John Wiley and Sons
• Year: 1970
• Tongue: English
• Weight: 389 KB
• Volume: 2
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550020202

✦ Synopsis

The kinetics of the gas-phase dehydrogenation of cyclopentane to cyclopentene is found to be consistent with a slow attack by a n I atom (step 4, text) on cyclopentane in the range 282-382OC. The measured rate constants fit the Xrrhenius equation, log k, = 11.95 f 0.08 -(24.9 f 0.23)/0 1 mole-l sec-l, where 8 = 2.303R T in kcallmole.

This leads to a value of 0.) = 24.3 f 1 kcal/mole and a bond dissociation energy DHO(O/~) = 94.9 f 1 kcal/mole. The latter value is identical with DHo(i-Pr-H) = 95 f 1 kcal/mole and signifies that cyclopentane and the cyclopentyl radical have the same strain energy. Arrhenius parameters are deduced for all six steps in the reaction mechanism. Surface reactions are shown to be unimportant.

Cyclopentyl iodide is an unstable intermediate in the reaction and the rate constant for its bimolecular formation from HI + cyclopentene is found to be log k, = 8.40 0.29 -(26.9 f 0.8)/8 1 mole-1 sec-l. Together with the rquilibrium constant, this yields for the unimolecular elimination of HI from cyclopentyl iodide, the rate constant, log k, = 13.3 * 0.3 -(42.8 f 1.2)/8sec-l.