As mentioned in Section 22-10, the Sandmeyer reactions, in which copper(I) ion catalyzes substitution of the nitrogen in arenediazonium salts by Cl, Br, or CN, take place by complex mechanisms involving radicals. Explain why these substitutions do not follow either the S_N1 or S_N2 pathway. 

Section 22-10

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Sandmeyer Reactions CH3 CH3 CH3 HN HCI, NANO,, 0°C N, Cl- Cl CuCl, 60°C -N2 79% overall 2-Methylbenzenamine (o-Methylaniline) 1-Chloro-2-methylbenzene (o-Chlorotoluene) .CI 1. HBr, NANO,, 0°C 2. CuBr, 100°C Cl `NH2 Br 73% 2-Chlorobenzenamine 1-Bromo-2-chlorobenzene (0-Chloroaniline) (o-Bromochlorobenzene) CH3 CH3 1. HCI, NANO, 0°C 2. CUCN, KCN, 50°c -> NH2 CN 70% 4-Methylbenzonitrile (p-Tolunitrile)