Consider the methyl substituted benzoic acids. 1. PhCOOH 2. o-CH3C6H4COOH 3. p-CH3C6H4COOH 4. m-CH3C6H4COOH The correct sequence of acidity is

Question

Consider the methyl substituted benzoic acids. 1. PhCOOH 2. o-CH3C6H4COOH 3. p-CH3C6H4COOH 4. m-CH3C6H4COOH The correct sequence of acidity is (A) 1 < 2 < 3 < 4 (B) 2 < 3 < 4 < 1 (C) 3 < 4 < 1 < 2 (D) 3 < 4 < 2 < 1

Tardigrade Admin · Accepted Answer

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

CO O^{-}

. This results in more effective electron-donation and acid-weakening. This makes

p - C H_{3} C_{6} H_{4} COO H

less acidic than

m - C H_{3} C_{6} H_{4} COO H

.

o - C H_{3} C_{6} H_{4} COO H

is a stronger acid than benzoic acid, due to ortho-effect.

p - C H_{3} C_{6} H_{4} COO H

<

m - C H_{3} C_{6} H_{4} COO H

< PhCOOH <

o - C H_{3} C_{6} H_{4} COO H

Q. Consider the methyl substituted benzoic acids. 1. PhCOOH 2. o−CH3​C6​H4​COOH 3. p−CH3​C6​H4​COOH 4. m−CH3​C6​H4​COOH The correct sequence of acidity is

1 < 2 < 3 < 4

2 < 3 < 4 < 1

3 < 4 < 1 < 2

3 < 4 < 2 < 1

Q. Consider the methyl substituted benzoic acids.

$1.$ PhCOOH

$2.$ $o - C H_{3} C_{6} H_{4} COO H$

$3.$ $p - C H_{3} C_{6} H_{4} COO H$

$4.$ $m - C H_{3} C_{6} H_{4} COO H$

The correct sequence of acidity is