Advices For Studying Organic Chemistry

3.10B AN EXPLANATION BASED ON INDUCTIVE EFFECTS

1. The inductive effect of the carbonyl group (C=O group) is responsible for the
   acidity of carboxylic acids.

CO

O

H 3 C < <

<

H H 3 C CH 2 O<H

Acetic acid Ethanol
(Stronger acid) (Weaker acid)

1) In both compounds the O—H bond is highly polarized by the greater

electronegativity of the oxygen atom.

2) The carbonyl group has a more powerful electron-attracting inductive effect than

the CH 2 group.

3) The carbonyl group has two resonance structures:

C

O O−

C+

Resonance structures for the carbonyl group

4) The second resonance structure above is an important contributor to the overall

resonance hybrid.

5) The carbon atom of the carbonyl group of acetic acid bears a large positive

charge, it adds its electron-withdrawing inductive effect to that of the oxygen

atom of the hydroxyl group attached to it.

6) These combined effects make the hydroxyl proton much more positive than

the proton of the alcohol.

2. The electron-withdrawing inductive effect of the carbonyl group also stabilizes the
   acetate ion, and therefore the acetate ion is a weaker base than the ethoxide
   ion.

CO

O

H 3 C <

<

G−

G−

CH^2 O

H 3 C < −