
TY  - JOUR
A1  - Brown, CE 
A1  - Neville, AG 
A1  - Rayner, DM 
A1  - Ingold, KU 
A1  - Lusztyk, J 
T1  - Kinetic and Spectroscopic Studies on Acyl Radicals in Solution by Time-Resolved Infrared Spectroscopy
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1995
VL  - 48
IS  - 2
SP  - 363
EP  - 379
KW  - 
UR  - https://doi.org/10.1071/CH9950363 
N2  - A number of acyl radicals, R&#266;=O, have been generated in hexane or di -t-butyl peroxide as solvent at room temperature by 308 nm laser flash photolysis, and their spectroscopic and kinetic properties have been examined by time-resolved infrared spectroscopy. The C=O stretching frequencies for the R&#266;=O radicals are found to be higher than those of the corresponding aldehydes, RCHO, by between 108 and 128 cm-1, an effect attributed to a higher C=O bond order in the radicals. For the R&#266;=O radicals some typical values of vC =O are: CH3&#266;=O, 1864 cm-1; (CH3)3C&#266;=O, 1848 cm-1; and C6H5&#266;=O, 1828 cm-1, while the corresponding acylperoxyl radicals, RC(O)OO, formed by reaction with oxygen have vC =O values of 1838, 1840 and 1820 cm-1, respectively. The acyl radicals exhibit a reactivity towards a variety of substrates that is roughly comparable to that of simple alkyl radicals. For reactions of the benzoyl radical some typical rate constants/M-1 s-1 are: CCl4, 6.0x104; C6H5SH, 4.8&#215;107; CCl3Br, 2.2&#215;108; Tempo, 1.1&#215;109; and oxygen, 1.8&#215;109. Alkanoyl radicals have a rather similar reactivity to benzoyl. The propanoyl radical reacts with tributyltin deuteride with a rate constant of 3&#215;105 M-1s-1. The hex-5-enoyl radical undergoes a 5-exo-trig cyclization to form the 2-oxocyclopentylmethyl radical with a rate constant of 2.2&#215;105 s-1, a value which is almost identical to that for cyclization of the hex-5-enyl radical. It is hoped that our kinetic data will prove useful in the planning of organic synthetic strategies which involve acyl radical chemistry. 
ER  -

