Aromatic carboxylic acids are organic compounds that contain both a carboxyl functional group (-COOH) and an aromatic ring, which is a cyclic arrangement of atoms with alternating double bonds. These compounds are also known as aryl carboxylic acids. Examples of aromatic carboxylic acids include benzoic acid, salicylic acid, and phenylacetic acid. These compounds are widely used in the pharmaceutical industry as starting materials for the synthesis of drugs, as well as in the food industry as preservatives due to their antimicrobial properties. Aromatic carboxylic acids are typically weak acids, meaning that they do not readily donate a proton (H+) to a solvent. This is due to the resonance stabilization of the aromatic ring, which delocalizes the negative charge of the carboxylate ion (-COO-) over the ring, making it less reactive. However, under certain conditions, such as in the presence of a strong base, these acids can undergo deprotonation to form the corresponding carboxylate salt.

1. AROMATIC CARBOXYLIC ACIDS

2.  Aromatic acids are compounds in which one
or more carboxyl groups (-COOH) are
attached directly to the aromatic ring.

3. COOH
Benzoic acid
COOH
OH
Salicylic acid
COOH
Cl
4-chlorobenzoic acid
COOH
COOH
terephthalic acid
COOH
phthalic acid
COOH
terephthalic acid
COOH
COOH
isophthalic acid

4.  The aromatic carboxylic acids are generally
crystalline solids with high melting point.
 They are soluble in hot water and organic
solvents.
solvents.
 Benzoic acid is a colourless solid; m.p. 122°
C. It is soluble in hot water, diethyl ether,
ethanol and benzene.

5.  Oxidation Reactions
◦ Oxidation of Alkyl benzene
◦ Example

6. ◦ Oxidation of Primary aromatic alcohols
◦ Oxidation of Aromatic carbonyl compounds
CHO
Benzaldehyde
COOH
Benzoic acid
KMnO4/OH+

7.  Hydrolysis Reaction
◦ Hydrolysis of Aromatic Nitriles

8.  Hydrolysis of Esters

9.  Sandmeyer’s Reaction
◦ Aniline on diazotization gives benzenediazonium
chloride which on reaction with CuCN produce
Benzonitrile. Benzonitrile, in the presence of water
gives benzoic acid via formation of an amide.
◦

10.  From Sulphonic Acid
◦ When the potassium salt of an aromatic sulphonic
acid is fused with potassium cyanide, we get a
nitrile, which on hydrolysis, gives an aromatic acid
via formation of an amide.

11.  Reaction of benzoic acid are divided into -:
◦ Reaction of COOH group
◦ Salt Formation
◦ Benzoic acid reacts with sodium hydroxide or
sodium bicarbonate to form sodium benzoate.

12.  Acyl Halide Formation
◦ Benzoic acid reacts with phosphorus pentachloride
or thionyl chloride to form benzoyl chloride.

13.  Ester Formation
 Reduction to Benzyl alcohol
 Benzoic acid undergoes reduction with
lithium aluminium hydride gives benzyl
alcohol.

14.  Decarboxylation
 Reaction of Benzene Ring
Nitration of Benzoic acid
Uses- Benzoic acid is used in mouth washes
because it inhibits bacterial growth.

15.  The acidic strength of aromatic carboxylic
acid is attributed to resonance stabilization of
of carboxylate ion formed by loss of proton.

16.  The presence of electron withdrawing groups
increases the acidic strength as these groups
delocalize the negative charge and stablize
the carboxylate ion.
 However, the electron releasing groups
decrease the acidic strength by intensifying
the negative charge and thus destabilize the
carboxylate ion.