Finally, we were interested to compare quantitatively LBR I with some other commonly used halogen abstractors, including -aminoalkyl and (tris(trimethylsilyl)silyl radicals and a conventional tin-based XAT reagent (Me3Sn • ). As depicted in Figure , a clear trend emerges. On the one hand, the XAT step shows very low activation energies in the case of metalloidyl radicals (i.e., R3Si • and R3Sn • ; for the tin-based abstractor it is essentially barrierless); while LBR I and the -aminoalkyl radical display significant G ‡ values (+11.6 and 15.0 kcal•mol -1 , respectively). On the other hand, from a thermodynamic point of view, the XAT process is highly exergonic for metalloidyl radicals, moderately exergonic for LBR I and essentially thermoneutral for the amino radical. In the latter case, the formation of an iminium ion resulting from the elimination of iodide was invoked as the driving force for the whole process. Taken both experimental and computational insights together, a realistic mechanistic scenario can be portrayed as shown in Figure . First, we considered the near UV-induced hydroalkylation methodology. Here, alkyl iodides undergo direct photolysis to yield C-centered radicals (see also Section 6.2 in the Supporting Information). 28 These nucleophilic radicals can (i) directly abstract a hydrogen atom from B1 or (ii) add onto the electron-poor olefin to give a stabilized radical that then triggers a HAT step from B1. In both cases, the same LBR would be formed. By comparing the results shown in Table (entries 5 and 10), and capitalizing on our DFT analysis, we found that these are two kinetically competent scenarios; however, under optimized conditions, the addition onto the Michael acceptor is faster. Notably, this experimental observation is also evident from the polarity mismatch between the nucleophilic alkyl radical (II) and the hydridic B-H bonds of B1. In contrast, the radical adduct generated upon radical addition (III) is an electrophilic radical, thus making the HAT step from B1 now polarity-matched. This specific event now starts the radical chain mechanism.