Figure 3.

Reaction between alpha-aminoalkyl radical and HEMA monomer. Equilibrium structures of (a) reactant, (b) TS, and (c) product are determined using unrestricted M06/6-311G(d,p)/CPCM-methanol. The enthalpic barrier for this reaction is determined to be ΔH⁰_act = −1.4 kcal/mol, after zero-point-energy (ZPE) and thermal corrections to 298 K. Note that although ΔE⁰_act is positive, thermal and zero-point corrections often produce a negative ΔH⁰_act for reactions that are essentially barrierless.