Products of the gas-phase OH radical-initiated reactions of 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone

✍ Scribed by Roger Atkinson; Sara M. Aschmann

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 843 KB
• Volume: 27
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550270305

✦ Synopsis

The gas-phase reactions of the OH radical with 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone have been investigated in the presence of NO,. Acetone and 2-methylpropanal were identified and quantified as products of both reactions. The acetone yield from 2,6-dimethyl-4-heptanone increased after addition of NO to reacted mixtures, indicating that acetone is formed through the intermediary of an acyl radical. The acetone and 2-methylpropanal formation yields were determined to be 0.78 2 0.06 and 0.071 ? 0.011, respectively, from 4-methyl-2-pentanone and 0.68 i_ 0.11 and 0.385 i 0.034, respectively, from 2,6-dimethyl-4-heptanone. The possible reaction mechanisms are discussed and compared with these product data, and it is concluded that the experimental data provide direct evidence for isomerization of the (CH3)zCHCHzC(O)CHzC(O) (CH3)z alkoxy radical formed from 2,6-dimethyl-4-heptanone. However, the isomerization rates of the alkoxy radicals formed from the ketones depend on whether the H-atom abstracted is on a carbon atom (Y or p to the >C=O group, with H-atom abstraction from C-H bonds on the p carbon atoms being significantly faster than from C-H bonds on the a carbon atoms.