121776-79-2Relevant articles and documents
Kinetic and Spectroscopic Studies on Acyl Radicals in Solution by Time-Resolved Infrared Spectroscopy
Brown, Carl E.,Neville, Anthony G.,Rayner, David M.,Ingold, Keith U.,Lusztyk, Janusz
, p. 363 - 380 (2007/10/02)
A number of acyl radicals, R=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=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=O radicals some typical values of νC=O are: CH3=O, 1864 cm-1; (CH3)3C=O, 1848 cm-1; and C6H5=O, 1828 cm-1, while the corresponding acylperoxyl radicals, RC(O)OO, formed by reaction with oxygen have νC=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-1s-1 are: CCl4, 6.0*104; C6H5SH, 4.8*107; CCl3Br, 2.2*108; Tempo, 1.1+109; and oxygen, 1.8*109.Alkanoyl radicals have a rather similar reactivity to benzoyl.The propanoyl radical reacts with tributyltin deuteride with a rate constant of 3*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*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.
