Alkoxy radical isomerization in the OH radical-initiated reactions of C-4-C-8 n-alkanes

Isomerizations of the alkoxy radicals formed from the OH radical reactions with n-butane through n-octane and n-pentane-d(12) through n-octane-d(18) have been studied in the presence of NO at 296 +/- 2 K and 740 Torr total pressure of air, In addition to carbonyls of the same carbon number as the alkane precursors, the previously predicted sigma-hydroxycarbonyls were detected by direct air sampling atmospheric pressure ionization triple quadrupole mass spectrometry. The formation yields of carbonyl compounds containing the same number of carbons as the parent n-alkane decreased with increasing carbon number in the n-alkane, while the hydroxycarbonyl/carbonyl formation yield ratios increased markedly from n-butane through n-octane, in agreement with previous theoretical predictions.