text: The standard preparation for n-BuLi is reaction of 1-bromobutane or 1-chlorobutane with Li metal:
  : 2 Li + CHX  →  CHLi  +  LiX  (X = Cl, Br)
  If the lithium used for this reaction contains 1–3% sodium, the reaction proceeds more quickly than if pure lithium is used.  Solvents used for this preparation include benzene, cyclohexane, and diethyl ether.  When BuBr is the precursor, the product is a homogeneous solution, consisting of a mixed cluster containing both LiBr and BuLi, together with a small amount of octane.  BuLi forms a weaker complex with LiCl, so that the reaction of BuCl with Li produces a precipitate of LiCl.
  Solutions of butyllithium, which are susceptible to degradation by air, are standardized by titration.  A popular weak acid is biphenyl-4-methanol, which gives a deeply colored dilithio derivative at the end point.