Acetylide ions halogenation

In principle, nucleophilic attack can occur at several different locations in a haloalkyne at the halogenated carbon in the triple bond [Eq. (75b)], at the halogen itself [Eq. (75a)l, and at the second carbon in the triple bond [Eq. (75c)]. All three of these possibilities are observed in reactions with haloalkynes and sodium methoxide in methanol. The mechanisms of some of these substitution reactions are not clear, and acetylide ion intermediates, RC may be involved. 

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