THERMAL DECOMPOSITION OF ACETALDEHYDE STUDIED BY MATRIX IR AND PIMS SPECTROSCOPY
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Date
2010
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Publisher
Ohio State University
Abstract
In all previous experimental studies of the thermal decomposition of acetaldehyde (CH$_3$CHO), the products were presumed to be CH$_3$ + CHO. These species result from cracking of the weakest bond. Other routes are possible: (DH$_{298}$(CH$_3-$CHO) = 84.8 $\pm$ 0.2 kcal mol$^{-1}$; DH$_{298}$(CH$_3$CO-H) = 89.4 $\pm$ 0.3 kcal mol$^{-1}$; DH$_{298}$(H-CH$_2$CHO) = 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 $\mu$sec 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: enter{CH$_3$CHO} + $\Delta \rightarrow$ CH$_3$CO + H\\ enter $\rightarrow$ CH$_2$=CHOH\\ enter $\rightarrow$ CH$_2$=C=O\\ enter $\rightarrow$ CH$_3$ + HCO\\
Description
Author Institution: University of Colorado, Boulder, CO 80309-0215; Center for Renewable Chemical, Technologies \& Materials, NREL, 1617 Cole Blvd., Golden, CO 80401; Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309-0427; Institute for Theoretical Chemistry, Department of Chemistry, University of Texas, Austin, TX 78712-0165