This document provides information on common essential drugs including benzoic acid, salicylic acid, aspirin, paracetamol, PABA, sulfa drugs, and PASA. It describes the structure, synthesis, properties and uses of each drug. Benzoic acid is used as a germicide and food preservative. Salicylic acid has analgesic and anti-inflammatory properties. Aspirin is used to reduce fever and pain. Paracetamol is an analgesic and antipyretic. PABA acts as a sunscreen and in vitamin synthesis. Sulfa drugs treat bacterial infections. PASA is used to treat tuberculosis.

1. Introduction to common essential Drugs
Benzoic Acid
It is the simplest aromatic carboxylic acid in which one carboxyl group (-COOH) is directly attached to
the aromatic ring. The structure of benzoic acid is designated as below-
Synthesis: Benzoic acid is synthesized by following methods-
1.By oxidizing of alkyl benzene with acidic potassium permanganate or sodium dichromate.
2.By acid hydrolysis of phenyl cyanide or benzonitride.
Properties:
1. Benzoic acid is a colorless solid
2. It’s melting point is 122°c
3. It is soluble in hot water, ether, ethanol, benzene and diethyl ether
4. It is stream volatile
5. It is slightly stronger acid than acetic acid.
Uses:
1. Benzoic acid is used as germicide in medicine for urinary infection and in vapour form for dis-
infecting bronchial tubes.
2. It is used as food preservation ; e.g.- sodium benzoate is used for preserving pickles, tomato
ketchup and fruit juices.

2. 3. In dye industry, it is used for preparing anile blue.
4. The combination of benzoic acid alcohol and water is used as cleaning agent in pharmacy.
5. It is used as an antibacterial and antifungal agent.
Salicylic Acid
Salicylic acid is a hydrobenzoic acid on which the carboxyl group(-COOH) is attached to the benzene ring
at “ortho” position. It’s structure is designated as below-
Synthesis: Salicylic acid is obtained by following process-
1. By heating sodium phenoxide and carbon dioxide at 125°C under pressure This process is
known as Kolbe reaction.
Properties:
1. Salicylic acid is colorless solid
2. It’s melting point is 159°C
3. It is insoluble in cold water but soluble in hot water, ethanol and ether.
4. It is steam volatile
5. It is stronger acid than benzoic acid.
Uses:
1. Prodrug of salicylic acid is aspirin that is an OTC drug.
2. It has analgesic or painkiller properties.
3. It is used as skin care to remove dead skin cells
4. Inflammation and skin irritation caused by burns, insect bite, fungal infection and eczema
are treated by it.
5. It is used as antidandruff, antiseptic and antibacterial agent.
6. It is used for food preservation.

3. Prodrug: It is the drug that is individually insert and becomes active after entering into body and
converts into main drug that shows biological action.Example—
Prodrug—Aspirin; Main drug-Salicylic acid.
Salicylic acid is not used directly because it causes stomach irritation and gastric problem. For these
reasons, it is used as the form of prodrug.
Acetyl-Salicylate Or Aspirin
Acetyl-Salicylic acid is an important derivation of salicylic acid. It is called Aspirin as trade name. It’s
structure is designated as-
Synthesis: It is prepared by heating salicylic acid with acetyl chloride or acetyl anhydride in the
presence of phosphoric acid.
Properties:
1. It is a colorless solid
2. It’s melting point is 135°c
3. It is odorless.
Uses:
1. It is used to reduce fever without lowering body temperature.
2. It is also a painkiller and used to treat headache, muscle & joint ache.
3. It reduces swelling and treats inflammation.
4. It is used to the treatment of rheumatic fever and rheumatic arthritis.
5. It is also used as additive in food, animal feed, drug and cosmetic
6. It is used to treat common cold.

4. Paracetamol
Paracetamol is para acetyl amino phenol. It’s structure is designated as below-
Synthesis: It is prepared by the reduction of para nitrophenol by NaBH4.And then the product para
amino phenol reacts with acetic anhydride to produce paracetamol.
Properties:
1. It is a white crystalline powder
2. It’s melting point is 170°c
3. It is odorless and has slightly bitter taste.
4. It is slightly soluble in water and soluble in most of the organic solvents
Uses:
1. It is an analgesic and used to relieve pain.
2. It has antipyretic property and so it reduces fever.
3. It can treat cold.
PABA
The full form of PABA is para amino benzoic acid. The structure of PABA is designated as- PABA is
considered to be in the B-complex vitamin family. It is not a vitamin; our body can make PABA from folic
acid at the time of special need.

5. Synthesis: When toluene gives nitration reaction at p-position; para nitro toluene is formed by
oxidizing the para nitro toluene; para nitro benzoic acid is obtained. When the p-nitro benzoic acid is
gone reduction by H2 & Pd-C catalyst; PABA is formed.
Properties:
1. It is white-grey crystal.
2. It’s melting point is 188°c
3. It is slightly soluble in water
4. It can block UV rays.
Uses:
1. It is used as UV screening and sun screening agent. It prevents skin cancer.
2. It helps in the formation of RBC & formely used as anti rickeltsial agent.
3. It is useful for the bacteria that synthesizes folic acid in human
4. It acts as co-enzyme for the metabolism of protein and it’s utilization
5. It is an anti oxidant
6. It helps to restore color of grey hair of human.
Sulfa Drug
Sulfa drugs are the group of drugs derived from sulfonamide compounds that inhibit the activity of
bacteria and are used in medicine to treat bacterial infection. The structure of sulfonamide/
sulfanilamide is designated as-
Hydrogen of Sulfo amide group

6. When the NH2 SO2NH H is substituted by various groups; the derivation of sulfa drugs are
formed such as-
Synthesis: It is prepared from acetanilide by following steps—
Properties:
1. It is a white crystalline solid
2. It’s melting point is 166.5°c
3. It has anti microbial properties
Uses:
1. Sulfa drugs are used to treat pneumonia gonorrhea etc caused by microorganisms
2. It is used to treat eye infection
3. Sulfa drugs- sulfadiazine is used to treat meningitis & urinary tract disorders
4. Sulfa drugs are used in the treatment of inflammatory bowel disease
5. It also helps to reduce allergies
Kernicterus: it is brain damage due to excess bilirubin; is the effect of sulfa drugs.

7. PASA
The full form of PASA is para- amino salicylic acid. The structure is
Synthesis:( Kolbe synthesis reaction)
Amino phenol reacts with alkyl magnesium bromide and then CO2 and at the end in acidic medium
reaction with water reacts para amino salicylic acid.
Properties:
1. PASA is a white crystalline solid
2. It’s melting point is 150°c
3. It is soluble in water and polar organic solvent
Uses:
1. It is used to treat tuberculosis
2. It is used to the treatment of inflammatory bowel disease
3. It is also used in pregnancy category
4. It is used in manganese chelation therapy.
Tanzir Ahmed
141021