JEE MainChemistryGeneral Organic Chemistry
Consider the molecule hexane-2,4-dione with the labeled hydrogen atoms: CH ₃^ (a) - C (= O )- CH ₂^ (b) - C (= O )- CH ₂^ (c) - CH ₃^ (d) The correct decreasing order of acidic strength of the labeled protons is:
Options
- Ab > c > a > d
- Bb > a > c > d
- Ca > b > c > d
- Db > a > d > c
Correct answer
B. b > a > c > d
Step-by-step solution
The acidic strength of a proton depends on the stability of the carbanion formed after its removal. Proton (b) is part of an active methylene group flanked by two electron-withdrawing carbonyl groups. Its conjugate base is highly stabilized by resonance over two oxygen atoms, making it the most acidic. Protons (a) and (c) are alpha to only one carbonyl group. Removal of proton (a) yields a primary carbanion, whereas removal of proton (c) yields a secondary carbanion. Due to the electron-donating inductive effect (+