Q.Answer the following :
Write two examples of the following.
a. Analgesics c. Antiseptics d. Antibiotics e. Disinfectant

Aspirin (acetylsalicylic acid) relieves pain (analgesic) and reduces fever (antipyretic) by blocking prostaglandin synthesis.

Each drug acts on a specific target:

• Aspirin inhibits the cyclooxygenase (COX) enzyme that makes prostaglandins, the chemicals responsible for pain, fever and inflammation. Blocking COX gives aspirin analgesic, antipyretic, AND anti-inflammatory action together — it is even used in low doses as an antiplatelet agent.

• Penicillin is an antibiotic (kills bacteria) — unrelated to pain/fever.

• Morphine is a narcotic analgesic (relieves severe pain) but is not antipyretic.

• Seldane (terfenadine) is an antihistamine, used for allergies.

Paracetamol is N-(4-hydroxyphenyl)acetamide — a phenol ring with a para -OH and an acetamide (-NHCOCH$_3$) group — matching structure (c).

Paracetamol (acetaminophen) is chemically 4-hydroxyacetanilide, i.e. acetanilide (C$_6H_5$-NHCOCH$_3$) with an additional -OH group at the para position:

$HO\text{-}C_6H_4\text{-}NHCOCH_3$

This has an -NHCOCH$_3$ (acetamido) substituent — an amide of aniline — and a para -OH (phenolic) group, which is exactly structure (c).

The other structures don't match: (a) and (b) are benzamide derivatives (-CONH$_2$ directly on the ring, not an N-acyl amine), and (d) is a ketone (4-hydroxyacetophenone, -COCH$_3$), not an amide.

Drugs that counteract the effects of histamine (released during allergic reactions) are called antihistamines.

When the body encounters an allergen, it releases histamine, which causes symptoms like sneezing, itching, watery eyes and swelling. Drugs that interfere with the natural action of histamine — by competitively blocking histamine receptors — are called antihistamines (e.g. Diphenhydramine, Terfenadine, Brompheniramine).

Paracetamol is N-(4-hydroxyphenyl)acetamide.

Paracetamol (acetaminophen) is N-(4-hydroxyphenyl)acetamide — a benzene ring bearing a phenolic -OH group and, para to it, an acetamido group (-NHCOCH3). This matches option (b).

An antibiotic is a substance (often produced by one microorganism) that kills or halts the growth of pathogenic microbes without seriously harming the host; penicillin is the classic historical example.

DEFINITION: Antibiotics are chemical substances, produced (wholly or partly) by microorganisms, that in low concentrations either kill (bactericidal) or inhibit the growth (bacteriostatic) of other, disease-causing microorganisms, while being administered to a patient with minimal toxicity to human cells.

EXAMPLE: Penicillin, discovered by Alexander Fleming from the mould Penicillium notatum, is a widely used antibiotic effective against many Gram-positive bacterial infections; it works by interfering with bacterial cell-wall synthesis.

(Other equally valid examples include streptomycin, chloramphenicol, ofloxacin, and erythromycin.)

Antipyretic drugs lower an abnormally high body temperature (fever) back toward normal.

Antipyretics are drugs that are used to bring down an abnormally elevated body temperature (fever) to normal. They work by acting on the body's temperature-regulating centre (in the hypothalamus).

Example: Paracetamol (acetaminophen) is a very common antipyretic, widely used to treat fever. (Aspirin also has antipyretic action, in addition to its analgesic and anti-inflammatory effects.)

Among the four drugs listed, only chloramphenicol is an antibiotic — the other three belong to different drug classes.

Drugs are classified by the biological target/effect they act on:

• Chloramphenicol is a broad-spectrum antibiotic, used against a wide range of gram-positive and gram-negative bacterial infections by inhibiting bacterial protein synthesis.

• Aspirin (acetylsalicylic acid) is an analgesic-antipyretic (and anti-inflammatory) drug, not an antibiotic.

• Veronal (barbital) is a barbiturate, used as a sedative/hypnotic (tranquilliser), not an antibiotic.

• Foristal is an antihistamine, used to counter allergic reactions, not an antibiotic.

Antacids are mild bases; they neutralise the excess stomach acid (HCl) through an ordinary acid–base neutralisation reaction.

Gastric (stomach) juice contains hydrochloric acid, needed for digestion, but excess secretion causes discomfort/acidity. Antacids are mild bases (e.g., magnesium hydroxide, aluminium hydroxide, sodium bicarbonate) that work by simple acid–base neutralisation: the basic antacid reacts with and consumes the excess HCl, raising the stomach's pH back towards normal and relieving the acidity.

Example: $Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O$