1H NMR Study of Hydrogen Abstraction in Model Compound Mimics of Polymers

Small molecules representing common synthetic polymers were subjected to photochemically induced hydrogen abstraction by benzophenone. Reactions were monitored using H-1 NMR to query the factors that influence preferential abstraction of protons in unique chemical environments. Differences in bond dissociation energies do not fully explain the observed hydrogen abstraction preferences. To that end, we identify contributions to abstraction from prereactive complexation, radical stability, steric effects and charge transfer effects. Using representative small molecule model compounds in lieu of polymeric materials is a novel approach to understanding photochemical reaction in polymers; however, it cannot probe the contributions of macromolecular effects-e.g. polymer rigidity or side chain and backbone mobility-to preferential hydrogen abstraction.