Generation and reactivity of a lactone derived radical

The behavior of a lactone derived acrylate monomer (LacA) representative of Highly Reactive Acrylate Monomers (HRAM) and, for comparison, IsoDecyl Acrylate (IDA), is studied. Time resolved absorption spectroscopy allows the direct detection of the lactone derived radical Lac formed through a hydrogen abstraction reaction between LacA and the benzophenone triplet state or the t-butoxyl radical. Interestingly, Lac is almost not sensitive to oxygen (rate constant <5 × 106 M−1 s−1). Quantum mechanical calculations appear powerful to characterize the radical absorption spectrum (at 386 nm) and the spin density (0.8) of Lac, the reaction enthalpy (−52.1 kJ/mol) and the barrier (7.9 kJ/mol) for the Lac/O2 reaction. This computational approach allows a discussion of the Lac reactivity.