Complete the following reaction sequence : HC ≡ CH ⟶ LiNH 2 A CH 3 CH 2 Cl B ⟶ HBr C . Comment on the acidic nature of B .

Ethyne has acidic character. It reacts with strong base lithium amide ( LiNH 2 ) and forms lithium acetylide. Lithium acetylide reacts with ethyl chloride via SN 2 reaction and forms but-1-yne. But-1-yne reacts with HBr according to Markovnikov's rule and gives 2,2-dibromo butane. CH 3 - CH 2 - C ≡ CH The compound 'B' is but-1-yne, which is a terminal alkyne. In terminal alkyne, a hydrogen atom is directly attached to sp hybridized carbon atom. In sp hybrid orbital, the percentage of s -character is 50 % . An electron in s -orbital is very close to the nucleus and is held tightly. The sp hybrid carbon atom in terminal alkynes is more electronegative than the sp 2 carbon in ethene or the sp 3 carbon in ethane. Due to high electronegative character of carbon in terminal alkynes, a hydrogen atom can be given away as proton ( H + ) to a very strong base. That is, but-1-yne has acidic character.