Presentation Title

Determination of Relative Rate Constants for Iodine Atom Abstraction By Phenyl Radicals

Abstract

Phenyl radicals (Ph·) are efficient hydrogen atom abstractors, and this reaction may have biological significance. However, the rate constants for H-abstraction from biomolecules (kH) by Ph· are predominantly not known. Previous work from the Nalli lab used the reaction of phenyl radicals with iodoarenes (lit kI = 1.0 x 108 M-1 s-1) as a kinetic reference for measuring k. However, this literature kI value we have come to realize is unreliable. My research used the photolysis of p-fluorophenylazoisobutyronitrile (FPhAIN) to make p-fluorophenyl radicals in the presence of CCl4 and an iodoarene (ArI). The products, p-chloro- and p-iodofluorobenzene (eq. 1) are measured using F-19 NMR, and the yield ratio allows the determination of the relative rate constant kI/kCl (eq. 2), which in conjunction with a well-established kCl gives kI. The results are compared to those reported by Tanner, Reed, and Setiloane in a 1982 paper that was later retracted.

College

College of Science & Engineering

Department

Chemistry

Location

Winona, MN

Breakout Room

1

Start Date

4-14-2021 2:00 PM

End Date

4-14-2021 2:45 PM

Presentation Type

Poster (PDF)

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Apr 14th, 2:00 PM Apr 14th, 2:45 PM

Determination of Relative Rate Constants for Iodine Atom Abstraction By Phenyl Radicals

Winona, MN

Phenyl radicals (Ph·) are efficient hydrogen atom abstractors, and this reaction may have biological significance. However, the rate constants for H-abstraction from biomolecules (kH) by Ph· are predominantly not known. Previous work from the Nalli lab used the reaction of phenyl radicals with iodoarenes (lit kI = 1.0 x 108 M-1 s-1) as a kinetic reference for measuring k. However, this literature kI value we have come to realize is unreliable. My research used the photolysis of p-fluorophenylazoisobutyronitrile (FPhAIN) to make p-fluorophenyl radicals in the presence of CCl4 and an iodoarene (ArI). The products, p-chloro- and p-iodofluorobenzene (eq. 1) are measured using F-19 NMR, and the yield ratio allows the determination of the relative rate constant kI/kCl (eq. 2), which in conjunction with a well-established kCl gives kI. The results are compared to those reported by Tanner, Reed, and Setiloane in a 1982 paper that was later retracted.