'''Butyllithium''' may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis:
*''n''-Butyllithium, abbreviated BuLi or <sup>n</sup>BuLi *''sec''-Butyllithium, abbreviated ''sec''-BuLi or <sup>s</sup>BuLi, has 2 stereoisomers, but is commonly used as racemate *''tert''-Butyllithium, abbreviated ''tert''-BuLi or <sup>t</sup>BuLi *Isobutyllithium
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