The kinetics of thiyl radical-induced reactions of monounsaturated fatty acid esters.
The time-dependent isomerizations and thiol additions of several Z- and E-monounsaturated fatty acid methyl esters catalyzed by alkanethiyl radicals during gamma-radiolysis of tert-butyl alcohol solutions are analyzed on the basis of the radiation chemical yield of radicals and established rate data. This provides room-temperature rate constants for the reversible thiyl addition. Within experimental errors, they do not depend on the double bond position in the alkyl chains. Particularly noteworthy is the very fast beta-elimination of thiyl radicals from alkyl radicals which carry a second beta-substituent. It is supported by additional evidence obtained with a radical clock methodology, and the large preference of fragmentation to the E-isomers is attributed to different barriers for the formation of the E- and Z-transition states from the equilibrium radical structure.
Chatgilialoglu
Chryssostomos
C
ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy. chrys@area.bo.cnr.it
Altieri
Alessio
A
Fischer
Hanns
H
D005227:Fatty Acids / Q000737:chemistry*; D005229:Fatty Acids, Monounsaturated / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D007536:Isomerism; D007700:Kinetics; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D020002:tert-Butyl Alcohol / Q000737:chemistry
D005227:Fatty Acids; D005229:Fatty Acids, Monounsaturated; D005609:Free Radicals; D013438:Sulfhydryl Compounds; D020002:tert-Butyl Alcohol