Application 1 — Acetanilide as Analgesic (Historical)

Acetanilide (CC(=O)Nc1ccccc1) was the first synthetic analgesic (pain reliever) and antipyretic (fever reducer), introduced in 1886. It is metabolized to paracetamol (acetaminophen) in the body. However, it also forms aniline as a metabolite, causing methemoglobinemia (reduced oxygen-carrying capacity of blood), which is why it was replaced by paracetamol.

Application 2 — Acetanilide as Protecting Group in Synthesis

In organic synthesis, the -NH2 group of aniline is acetylated to -NHCOCH3 (acetanilide) before nitration. Reason: direct nitration of aniline gives meta product (because -NH2 is protonated in strongly acidic HNO3 conditions, becoming -NH3+ which is meta-directing) and also gives over-nitration and oxidation. Acetylation: (1) protects the amine, (2) moderates ring activation, (3) ensures para selectivity. After nitration, hydrolysis removes the acetyl group to regenerate -NH2 as p-nitroaniline.

Application 3 — Iodoform as Antiseptic

Iodoform (CHI3) is a yellow, crystalline solid with a characteristic antiseptic smell. It was historically used as a wound antiseptic (iodoform gauze dressings) because it slowly releases iodine (I2) on decomposition. Modern iodine-based antiseptics (povidone-iodine) have largely replaced it.

Application 4 — KMnO4 Titration in Industrial Analysis

KMnO4/oxalic acid titration is used industrially to standardize KMnO4 solutions for use in water treatment, textile bleaching, and analytical chemistry. The self-indicating property makes it practical without requiring indicator reagents.

Application 5 — Lassaigne's Test in Drug Analysis

The Lassaigne's test is used in pharmaceutical analysis to confirm elemental composition of newly synthesized drugs. A compound claimed to contain N, S, and Cl must show: blood-red FeCl3 test (N+S), and white AgCl precipitate. Discrepancies alert chemists to synthesis errors.