The reaction channels of Znn and Mgn clusters (n ¼ 4, 10) with RCl organochlorides are compared to the investigation of relative activity of metals in the reaction of Grignard reagent formation within a framework of quantum chemical modeling of a reaction path. R radicals are chosen from a list of alkyl (CH3, C2H5, i-C3H7, and t-C4H9) and residues with p-bond (C2H3 and C6H5). Quantum chemistry calculations are made using the density function theory DFT) approach at the B3PW91/6-311þG(d) level. The reaction channels for both zinc and magnesium can be classified as radical and nonradical according to the nature of reaction products. The calculation of activation energies shows much similarity in their dependence on the nature of R radical but in the case of zinc, barriers are significantly higher. Both for zinc and magnesium clusters, the radical channels are more preferable in the case of alkyl residues, for vinyl and phenyl residues barriers of radical and nonradical channels are comparable