ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A value of the enthalpy of formation of the phenoxy radical in the gas phase, ΔH°,298K (φO·, g) = 11.4 ± 2.0 kcal/mol, has been obtained from the kinetic study of the unimolecular decompositions of phenyl ethyl ether, phenyl allyl ether, and benzyl methyl etherTrivial names for ethoxy benzene, 2-propenoxy (allyloxy) benzene, and α-methoxytoluene, respectively at very low pressures. Bond fission, producing phenoxy or benzyl radicals, respectively, is the only mode of decomposition in each case. The present value leads to a bond dissociation energy BDE(φO - H) = 86.5 ± 2 kcal/mol,1 kcal = 4.18674 kJ (absolute) in good agreement with recent estimates made on the basis of competitive oxidation steps in the liquid phase. A comparison with bond dissociation energies of aliphatic alcohols, BDE(RO - H) = 104 kcal/mol, reveals that the stabilization energy of the phenoxy radical (17.5 kcal/mol) is considerably greater than the one observed for the isoelectronic benzyl radical (13.2 kcal/mol). Decomposition of phenoxy radicals into cyclopentadienyl radicals and CO has been observed at temperatures above 1000°K, and a mechanism for this reaction is proposed.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550090202
