Free-radical addition of 2-(perfluoroalkyl)ethanethiols to alkenes, alkadienes, cycloalkenes, alkynes and vinyl monomers

Article abstract of DOI:10.1016/S0022-1139(00)80097-4

The free-radical addition of 2-(perfluoroalkyl)ethanethiols (R_FCH2CH2SH) to alkenes, cycloalkenes, alkadienes and alkynes has been studied to determine: (1) the mode of reaction, i.e. the stereochemistry, regiochemistry and any skeletal changes: (2) the relative reactivity towards unsaturates of differing structures and classes as affected by the presence of the R_F group; and (3) the influence of the reaction conditions on the rate of addition or selectivity for different products.Adducts from 2-(F-hexyl)ethanethiol (1) and alkenes have been obtained in high yield,but containing small amounts of regio isomers.For example compound 1 with 1-heptene gave 1-<2-(F-hexyl)ethanethio>heptane (3, 96percent yield) as well as 2-<2-(F-hexyl)ethanethio>heptane (4, O.61percent) and 3-<2-(F-hexyl)ethanethio>heptane (5, 2.22percent). 1,6-Hexadiene and 1,7-octadiene gave chiefly linear adducts, i.e.R_FCH2CH2S(CH2)_nCH=CH2 (7, n=4; or 12, n=6, respectively) and R_FCH2CH2S(CH2)_nSCH2CH2R_F (8, n=6; or 14, n=8, respectively).A small amount (2-3percent) of cis- and trans-1-methyl-<2-(F-hexylethanethiomethyl>cyclohexane (13) isomers were present in 12.Compound 1 with 1,6-heptadiene gave 7-<2-(F-hexyl)etanethio>-1-heptene (9), the bis adduct, 1,7-bis-<2-(F-hexyl)ethanethio>heptane (11) and the cyclic adducts, cis- and trans-1-methal-2-<2-(F-hexyl)ethanethio>methylcyclopentane (10).The relative amounts of cyclic isomers depended on the reactant ratio.Compound 1 added readily with free-radical initiation to vinyl monomers such as styrene and vinyl acetate, and to phenyl acetylene, propargyl acetate and ethyl propynoate.These new addition products are useful as models for further study.