Preparation of Alkynes from Alkynyl Anions

Example of Double Dehydrohalr enation to Give an Alkyne 

Three equivalents of NaNH2 are necessary in the preparation of a terminal alkyne because, as this alkyne forms, its acidic terminal hydrogen (Section 13-2) immediately protonates an equivalent amount of base. Eliminations in liquid ammonia are usually carried out at its boiling point, -33°C. 

Because vicinal dihaloalkanes are readily available from alkenes by halogenation, this sequence, called halr enation-double dehydrohalogenation, is a ready means of converting alkenes into the corresponding alkynes. 

A Halogenation-Double Dehydrohalogenation Used in Alkyne Synthesis 

Illustrate the use of halogenation-double dehydrohalogenation in the synthesis of the alkynes 

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Preparation of Alkynes from Alkynyl Anions CHAPTER 13... 

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