Related Experiment Video
Updated: Aug 8, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
E.s.r. of free radicals in aqueous solutions of substituted pyrimidines
Abstract:
Reactions of OH radicals with methyl and ethyl derivatives of uracil, cytosine and thymine in aqueous solutions have been investigated. Photolysis of H2O2 was used to generate OH radicals and the radicals on the base derivatives were spin-trapped using t-nitrosobutane and identified with the help of e.s.r. spectroscopy. Addition of OH radicals was found to take place predominantly to the C(5)--C(6) double bond of the bases. H-abstraction from the methyl group occurred in the N(1) methyl derivatives of uracil, cytosine and thymine. Radicals formed by H-abstraction from the methyl group were also detected for 3-methyluracil, thymine, 1-methylthymine and 1-ethylthymine. Introduction of a methyl or ethyl group at the N(1) position of uracil, cytosine and thymine causes an increase in the C(6) proton coupling and a decrease in the N(1) splitting for radicals formed by OH addition at the C(5) position.
More Related Videos
Related Concept Videos
Electrophilic Aromatic Substitution: Overview
Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between the...
Nucleophilic Aromatic Substitution: Elimination–Addition
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Radical Reactivity: Steric Effects
Along with electronic factors, steric factors also account...
Spontaneous and Induced Mutations

