"Alkyl halides are not often found in terrestrial organisms, but the kinds of reactions they undergo are among the most important and well-studied reaction types in organic chemistry. ... Simple alkyl halides can be prepared by radical halogenation of alkanes, but mixtures of products usually result. ... Alkyl halides can also be prepared from alkenes by reaction with N-bromosuccinimide (NBS) to give the product of allylic bromination. ... Alcohols react with HX to form alkyl halides, but the reaction works well only for tertiary alcohols, R3COH. ... Alkyl halides also react with lithium metal to form organolithium reagents, RLi. In the presence of CuI, these form diorganocoppers, or Gilman reagents (LiR2Cu)."