No abstract

In our previous work [Edeleva et al. Chem. Commun. 2019, 55, 190–193], we proposed a versatile approach to the activation of the homolysis of an aldonitrone group–containing alkoxyamine by 1,3‐dipolar cycloaddition to a vinyl monomer. Both nitroxide‐ and alkoxyamine‐containing aldonitrones were found to be capable of reacting with the activated alkenes. In the present study, the kinetics of these reactions with 11 different vinyl monomers were investigated using EPR and NMR spectroscopy, and apparent activation energies as well as pre‐exponential factors were determined. The influence of monomer structure on the rate of the 1,3‐dipolar cycloaddition is discussed. For the vinyl monomers typically used in nitroxide mediated polymerization (styrene, methyl methacrylate) the rate coefficient of cycloaddition to the nitroxide is around k(353 K) ∼4 ⋅ 10−4 L mol−1 s−1, whereas for n‐butyl acrylate and methyl vinyl ketone we observed the fastest cycloaddition reaction with k(353 K)=8 ⋅ 10−3 and 4 ⋅ 10−2 L mol−1 s−1 respectively.

Because the C–ON bond homolysis rate constant kd is an essential parameter of alkoxyamine reactivity, it is especially important to tune kd without a major alteration of the structure of the molecule.