NTA Abhyas JEE Main2020ChemistryGeneral Organic ChemistryPractice
Consider the methyl substituted benzoic acids. 1 . PhCOOH 2 . o - C H 3 C 6 H 4 C O O H 3 . p - C H 3 C 6 H 4 C O O H 4 . m - C H 3 C 6 H 4 C O O H The correct sequence of acidity is
Options
- A1 < 2 < 3 < 4
- B2 < 3 < 4 < 1
- C3 < 4 < 1 < 2
- D3 < 4 < 2 < 1
Correct answer
C. 3 < 4 < 1 < 2
Step-by-step solution
Both p- and m-methyl groups are electron-donating and acid weakening. Hyperconjugation of p - C H 3 produces a little extra δ - on the ring carbon, bearing the C O O - . This results in more effective electron-donation and acid-weakening. This makes p - C H 3 C 6 H 4 C O O H less acidic than m - C H 3 C 6 H 4 C O O H . o - C H 3 C 6 H 4 C O O H is a stronger acid than benzoic acid, due to ortho-effect. p - C H 3 C 6 H 4 C O O H m - C H 3 C 6 H 4 C O O H o - C H 3 C 6 H 4 C O O H