Preparation
The main preparative reactions involve the elimination of
groups or ions from molecules, resulting in the formation of π bonds.
·
Acetylene itself is formed from the reaction of the inorganic
compound calcium carbide with water.
CaC2 +
2 H2O → Ca(OH)2 +
HC≡CH
·
Higher alkynes may be prepared by the action of
alkyl halides on sodium ethynide. Sodium ethynide can be obtained from acetylene by the action of
sodium or sodamide.
·
Alkynes are prepared by dehydrohalogenation
of vicinal dihalides, usually bromides, using
alcoholic solution of potassium hydroxide.
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