The heat of formation of the acetonyl radical VLPP studies of acetonyl bromide,isopropenylmethylether, and hexanedione-2,5 in a search for acetonyl stabilization energy

The decomposition of acetonyl bromide, isopropenylmethylether, and hexanedione-2,5 was studied using the very-low-pressure pyrolysis (VLPP) technique. The acetonyl radical is a product of each reaction. Arrhenius parameters determined are or acetonyl bromide ← acetonyl + Br: and for isopropenylmethylether ← acetonyl + CH₃: These lead to values of acetonyl stabilization energy (SE) of 0.8 and ?4.0 kcal/mol, respectively. Comparison of the pyrolyses of hexanedione-2,5 and 2,5-dimethylhexane indicate a value of SE ～ 2 kcal/mol. The total of these results is taken, along with previous work, to indicate that 0 ? SE ? 2 kcal/mol.