Question

Why sodamide is preferred over koh in preparation of alkynes to vicinal dihalides?

Answer 1

Both vicinal dihalides and geminal dihalides undergo dehydrohalogenation reaction with a strong base to give alkyne in fairly good yield. The reaction follows 1, 2-elimination mechanism. 1 the first step, the base employed is alcoholic KOH while in the subsequent step, we need a strong base like sodamide as vinyl halide is less reactive towards elimination.

NaNH2 is preferred over alc. KOH in the second step as alc KOH finds it difficult to fetch a hydrogen halide molecule as the two leaving groups are attached to sp2 hybridised irbon atoms.

Answer 2

Synthesis of Alkynes

Explanation:

• Both vicinal dihalides and geminal dihalides is the process of  dehydrohalogenation reaction with a solid base to give alkyne in fairly good yield
• The initial step, the base utilized is alcoholic KOH while in the consequent advance, we need a solid base like sodamide as vinyl halide is less reactive towards elimination
• Chlorine or bromine is utilized with a inert halogenated dissolvable like chloromethane to make a vicinal dihalide from an alkene
• The vicinal dihalide formed is then reacted with a solid base and heated to produce an alkyne