● Mild analgesics function by intercepting the pain stimulus at the source, often by interfering with
the production of substances that cause pain, swelling, or fever.
● Aspirin is prepared from salicylic acid.
● Aspirin can be used as an anticoagulant, in prevention of the recurrence of heart attacks and
strokes, and as a prophylactic.
● Penicillins are antibiotics produced by fungi.
● A beta-lactam ring is a part of the core structure of penicillins.
● Some antibiotics work by preventing cross-linking of the bacterial cell walls.
● Modifying the side-chain results in penicillins that are more resistant to the penicillinase enzyme.
Applications and skills
● Description of the use of salicylic acid and its derivatives as mild analgesics.
● Explanation of the synthesis of aspirin from salicylic acid, including yield, purity by recrystallization,
and characterization using IR and melting point.
● Discussion of the synergistic effects of aspirin with alcohol.
● Discussion of how aspirin can be chemically modifi ed into a salt to increase its aqueous solubility
and how this facilitates its bioavailability.
● Discussion of the effects of chemically modifying the side-chain of penicillins.
● Discussion of the importance of patient compliance and the effects of the over-prescription of
● Explanation of the importance of the beta-lactam ring on the action of penicillin.
● Students should be aware of the ability of acidic (carboxylic) and basic (amino) groups to form ionic
salts, for example soluble aspirin.
● Structures of aspirin and penicillin are available in the data booklet in section 37.
Introduction to penicillin