ABSTRACT
Alkynes are molecules that contain a carbon–carbon triple bond. This means that an alkyne has two, perpendicular π bonds. This renders alkynes quite reactive due to the extra electron density and makes alkynes reactive as bases and nucleophiles. Unlike alkenes, terminal alkynes are also reactive as acids and electrophiles: the terminal alkyne hydrogen is moderately acidic. In this chapter, readers are introduced to alkyne reactions. First, the reaction of alkynes as electrophiles is considered, where acetylide nucleophiles are formed and used to extend the alkyne carbon chain. Second, addition reactions, where a reagent is added to the alkyne π bond to produce alkene or saturated products, will be considered. Like alkenes, alkyne addition reactions proceed through cationic (carbocation or onium ion) intermediates, which dictate the regiochemical outcome of the addition. Alkyne addition reactions also tend to produce Markovnikov regiochemical products. Given the breadth of reactions that have been considered so far, retrosynthetic analysis is introduced as a means of rationally determining chemical syntheses of a desired product.
