Butane hybrid orbitals

The acidity of a hydrogen atom bound to a carbon atom increases when the % of atomic p orbital decreases in the hybridization of this carbon acetylene sp C) is thus much more acidic pKa = 24) than benzene sp C, pK = 37), itself more acidic than butane sp C, pA = 44). The acido-basic equilibrium between butyl lithium and acetylene (or benzene) is displaced towards the direction that is favorable for the reaction producing lithium acetylide (or phenyllithium) and butane (or benzene). 

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