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Give method of preparation of ethyne (Acetelene) from vicinal dihalides. |
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Answer» Solution :(a) (i) Alkenlhalide is OBTAINED by reaction of vicinal dihlaide with alcoholic potassium hdyroxide reaction and this alkynyl HALIDE on reaction with sodamide `(NaNH_(2))` gives alkyne. This reaction is called dehydrohalogenation. (ii) This alkinyl on reaction with sodamide `(NaNH_(2))` gives alkyne.  (b) It can obtained by the following reaction too, `underset("1,2-dibromoethane")(CH_(2)Br-CH_(2)Br)+underset("Alcoholic")(2KOH) rarr underset("Ethyne")(CH-=CH)+2KBr+2H_(2)O` According to reaction (a), it is carried out in two or according to reaction (b), it is carried out in ONE STEP. But second step of reaction (a) is difficult and hence, it can be made easy by ADDITION of `NaNH_(2)`. |
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