OH
COONa
OH
COOH
OCOCH 3
COOH
OH
O
Salicylic acid
Sodium salicylate
NaOH
+ CO 2
125 o C
4-7 atm
H + , H 2 O
Acetyl salicylic acid (Aspirin)
Acetylation
Sodium phenoxide
Na +
..
:
:
..
Aldehyde formation: Reimer–Tiemann reaction Treatment of a phenol
with chloroform (CHCl 3 ) and aqueous hydroxide introduces an aldehyde
group (À ÀCHO) onto the aromatic ring, generally ortho to the À ÀOH group.
A substituted benzalchloride is initially formed, but is hydrolysed by the
alkaline medium. Salicylaldehyde can be produced from phenol by this
reaction. Again, salicylaldehyde could be oxidized to salicylic acid, which
could be acetylated to aspirin.
OH
OH
CHO
Salicylaldehyde
+ CHCl 3
70 o C
aq. NaOH
Reaction with formaldehyde (formation of phenol–formaldehyde
resins) Phenol reacts with formaldehyde (HCHO) to produce orthohydroxymethylphenol, which reacts with phenol to produce ortho-(parahydroxybenzyl)-phenol. This reaction continues to form polymer.
OH
OH
OH
OH
CH 2 OH
+ HCHO
Phenol
Phenol
HCHO
Polymer
ortho-Hydroxymethylphenol
ortho-(para-Hydroxybenzyl)-phenol
H + or HO −
4.6.11 Aromatic amines: aniline
An amine has the general formula RNH 2 (1
amine), R 2 NH (2
amine) or
R 3 N (3
amine), where R ¼ alkyl or aryl group, e.g. methylamine CH 3 NH 2 ,
dimethylamine (CH 3 ) 2 NH and trimethylamine (CH 3 ) 3 N.
When an amino group (À ÀNH 2 ) is directly attached to the benzene ring,
the compound is known as aniline.
134
CH4 ORGANIC FUNCTIONAL GROUPS