Q7 / 160 · AP EAMCET 2020 (17 Sep Shift 1) · Chemistry
Decreasing order of acidity of the following terminal acetylenes is
- A(i) \(>\) (iii) \(>\) (ii) \(>\) (iv)
- Correct answerB(i) \(>\) (ii) \(>\) (iv) \(>\) (iii)
- C(i) \(>\) (iv) \(>\) (ii) \(>\) (iii)
- D(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 \(\text { (i) } > \text { (ii) } > \text { (iv) } > \text { (iii) }\)
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 \(\text { (i) } > \text { (ii) } > \text { (iv) } > \text { (iii) }\)
Hence, the correct answer is option: 'B'.