Thermal decomposition of cyclopentene and cyclopentene-d$sub 8$ in the gas phase

Journal Article · Wed Nov 28 04:00:00 EST 1973 · J. Amer. Chem. Soc., v. 95, no. 24, pp. 7933-7938

OSTI ID:4368580

Knecht, D A

The thermal decomposition of cyclopentene and cyclopentene-d/sub 8/ (72.4% C/sub 5/D/sub 8/, 23.3% C/sub 5/ 3.7% C/sub 5/H/sub 2/D/sub 5/, and 0.6% C/ sub 5/H/sub 3/D/sub 5/) was stdied in the gas phase at 450-530 deg C and 4-34 Torr in a static system. In the initial phases of the pyrolysis, the reaction proceeds mainly by dehydrogenation to form hydrogen and cyclopentdiene, but at greater exterts of decomposition the participation of minor reactions forming ethylene and propylene increases. The first order rate constarts for dehydrogenation obtained from pressure increase measurements and from hydrogen analysis can be represented for H/sub 2/and D/sub 2/ formation, respectively, by kH/sub 2/ (sec/sup -1/) = (0.63 plus or minus 0.01) x 10/sup 13/ exp (-57,800 cal mol/sup -1/RT) and k/sub D/sub 2/ (secsiSTA -1/) = (0.99 plus or minus 0.02) x 10/sup 13/ exp (-60,500 cal mol/ sup -1/RT). The analysis of HD/D/sub 2/ formed from cyclopentene-ds and of H/sub 2/D/sub 3/ formed from an equimolar mixture of cyclopertene and cyclo pentene-ds yields the respective isotope effects k/sub HD/k /sub D2/ = (0.82 plus or minus 0.01) exp (1250 cal mol/sup -1/ RT) and k/sub H2/k/sub D2/ = (0.637 plus or minus 0.006) exp (2500 cal mol/sup - 1/RT). In copyrolysis experiments carried to 5% completion in C/sub 5/H/sub 8/ and 1.7% completion in C/sub 5/D/sub 8/, the d ehydrogenation reaction appears to be mainly the elimination of a molecule of hydrogen with atomic reactions contributing not more than 2% of the total H/sub 2/ + D/sub 2/. The minor product ethylene was formed with negligible isotopic mixing, whereas propylene exhibited a significant degree of isotopic mixing. (auth)

• Research Organization: Univ. of Rochester, NY
• NSA Number: NSA-29-009884
• OSTI ID: 4368580
• Journal Information: J. Amer. Chem. Soc., v. 95, no. 24, pp. 7933-7938, Journal Name: J. Amer. Chem. Soc., v. 95, no. 24, pp. 7933-7938; ISSN JACSA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*DEUTERIUM-- ISOTOPE EFFECTS
CHEMICAL REACTION KINETICS
CYCLOALKENES
DEUTERIUM COMPOUNDS
N40220* --Chemistry--Inorganic
Organic
& Physical Chemistry--Isotopic Effects
PYROLYSIS