15min:

ANGAYLE VASILIOU, KRZYSZTOF PIECH, G. BARNEY ELLISON, University of Colorado, Boulder, CO 80309-0215; MARK R. NIMLOS, Center for Renewable Chemical, Technologies & Materials, NREL, 1617 Cole Blvd., Golden, CO 80401; JOHN W. DAILY, Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309-0427; JOHN F. STANTON, Institute for Theoretical Chemistry, Department of Chemistry, University of Texas, Austin, TX 78712-0165.

In all previous experimental studies of the thermal decomposition of acetaldehyde (CH₃CHO), the products were presumed to be CH₃ + CHO. These species result from cracking of the weakest bond. Other routes are possible: (DH₂₉₈(CH₃-CHO) = 84.8 \pm 0.2 kcal mol^-1; DH₂₉₈(CH₃CO-H) = 89.4 \pm 0.3 kcal mol^-1; DH₂₉₈(H-CH₂CHO) = 92 \pm 2 kcal mol^-1. This work explores the possibility of other thermal decomposition pathways, that result via C-H bond scission. We have used a resistively heated SiC tubular reactor with a 65 µsec residence time to study the thermal cracking of acetaldehyde. The decomposition products are identified by two independent techniques: 118.2 nm (10.487 eV) VUV photoionization mass spectroscopy and infrared absorption spectroscopy in a cryogenic matrix. The observed dissociation channels seem to be: \centerCH₃CHO + CH₃CO + H
\center CH₂=CHOH
\center CH₂=C=O
\center CH₃ + HCO