Decreasing order of acidity of the following terminal acetylenes is

Decreasing order of acidity of the following terminal acetylenes is
  1. (i) \(>\) (iii) \(>\) (ii) \(>\) (iv)
  2. (i) \(>\) (ii) \(>\) (iv) \(>\) (iii)
  3. (i) \(>\) (iv) \(>\) (ii) \(>\) (iii)
  4. (i) \(>\) (iii) \(>\) (iv) \(>\) (ii)

Solution

Let us consider the structure of respective conjugate bases (carbonions),
EWG \((-R)\) stabilise carbanions but EDG \((+R > +I)\) destabilise carbanions. [EWG : Electron withdrawing group EDG : Electron donating group] A stronger acid produces stable conjugate base. So, the order of acidity will be \(\text { (i) } > \text { (ii) } > \text { (iv) } > \text { (iii) }\)

Asked in: AP EAMCET 2020 (17 Sep Shift 1)

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