CHEMISTRY TEXTBOOK

For example :

Zn-Hg, conc. HCl

H 3 C C O + 4[H] ∆

CH 3

H 3 C C H 2 + H 2 O

(Acetone) CH 3

(propane)

CH 3 CH 2 CHO + 4[H]

Zn-Hg, conc. HCl

∆

CH 3 CH 2 CH 3 + H 2 O

(Propanal)

(Propane)

C O

H 2 N-NH 2

-H 2 O^ C^ N^ NH^2

KOH, HO-CH 2 -CH 2 -OH

∆^ CH 2 + N 2

(Carbonyl group

in aldehydes and

ketones)

(Hydrazone)

(Methylene group)

For example :

Wolf-Kishner reduction is used to

synthesize straight chain alkyl substituted

benzenes which is not possible by Friedel-

Crafts alkylation reaction.

12.8.4 Electrophilic substitution reactions:

Aromatic aldehydes and ketones undergo

electrophilic substitution reactions such as

nitration ,sulfonation and halogenation. The

aldehydic ( -CHO) and ketonic (>C=O)

groups are electron-withdrawing by inductive

as well as resonance effects. They deactivate

the benzene ring at ortho- and para- positions.

This results in the formation of meta-product.

For example ,

12.9 Chemical properties of carboxylic

acids :

12.9.1 Acidic character of carboxylic acids:

The carboxyl group (- COOH) imparts acidic

character to carboxylic acids. A carboxyl

group is made of -OH group bonded to a

carbonyl group. In aqueous solution the H

atom in OH of carboxyl group dissociates as

proton and carboxylate ion is formed as the

conjugate base,

R - COOH + H 2 O R - COO + H 3 O⊕

(carboxylate ion)

Carboxylate ion is resonance stabilized by

two equivalent resonance structures as shown

below.

CHO

+ HO NO 2

conc. H 2 SO 4

CHO

+ H 2 O

NO 2

(conc. HNO 3 )

(Benzaldehyde)

(m-Nitrobenzaldehyde)

C

O

O

R C

O

O

R C

O

O

R

(i) (ii) resonance

hybrid

Wolf-Kishner reduction :

C O

C 2 H 5

H 2 N-NH 2

-H 2 O

C N-NH 2

C 2 H 5

KOH, HO-CH 2 -CH 2 -OH

∆

CH 2 + N 2

C 2 H 5

(Ethyl phenyl ketone)

(Hydrazone)

(n-Propyl benzene)

C 2 H 5 CHO

H 2 N-NH 2

-H 2 O C 2 H 5 CH^ N^ NH 2

KOH, HO-CH 2 -CH 2 -OH

∆ CH^3 CH^2 CH^3 + N^2

(Propanal) (Hydrazone)

(Propane)

(i)

(ii)

(i)

(ii)