59527-22-9Relevant academic research and scientific papers
Determination of Addition Rates of Benzenethiyl Radicals to Alkynes by Flash Photolysis. Structures of Produced Vinyl-Type Radicals
Ito, Osamu,Omori, Ryoichi,Matsuda, Minoru
, p. 3934 - 3937 (1982)
The addition rate constants (k1) of substituted benzenethiyl radicals to CHCR (R = Ph, n-C3H7, and COOCH3) have been determined by flash photolysis.The Hammett reaction constants (ρ+) was estimated for each alkyne: ρ+(CHCPh) = +1.38, ρ+(CHCC3H7) = +1.34, and ρ+(CHCCOOCH3) = +1.28.A small ρ+ value for CHCCOOCH3 was attributed to a decrease in the polar effect in the transition state.Similar ρ+ values were estimated for the corresponding alkenes.A small difference in the ρ+ values suggests that the reactivities of the alkynes and alkenes toward a thiyl radical may be mainly determined by the thermodynamic stabilities of the produced radicals (PhSCH=C(*)R and PhSCH2C(*)HR).The rate constants (in M-1 s-1) for the benzenethiyl radical were as follows: k1(CH2=CHPh) = 2.0E7, k1(CHCPh) = 7.9E5, k1(CH2=CHCOOCH3) = 2.7E5, k1(CHCC3H7) = 1.4E4, k1(CH2=CHC4H9) = 1.0E4, and k1(CHCCOOCH3) = 8.3E3.The unpaired electron of PhSCH=C(*)COOCH3 may be localized, whereas the unpaired electron of PhSCH2C(*)HCOOCH3 is stabilized by the interaction with the ester group.The stability of PhSCH=C(*)Ph is intermediate between the linear ? radical and the localized ? radical.
