Skraup synthesis is an important method used for the preparation of quinoline and its derivatives. Quinoline is a bicyclic aromatic heterocyclic compound consisting of a benzene ring fused with a pyridine ring. It has the molecular formula C₉H₇N and is an important structural unit in many natural products, pharmaceuticals, dyes, and biologically active compounds. The Skraup synthesis is especially useful because it provides a general method for constructing the quinoline ring system from aniline and a suitable carbonyl compound, usually glycerol, in the presence of concentrated sulphuric acid and an oxidizing agent. The classical Skraup synthesis was developed by Zdenko Hans Skraup in 1880. In the original reaction, aniline is heated with glycerol, concentrated sulphuric acid, and an oxidizing agent such as nitrobenzene. The glycerol is converted into acrolein under the strongly acidic conditions. Acrolein then reacts with aniline, followed by cyclization and oxidation, to give quinoline. The overall reaction may be represented as: C₆H₅NH₂ + HOCH₂–CHOH–CH₂OH → C₉H₇N + 4H₂O In the presence of concentrated H₂SO₄ and an oxidizing agent such as nitrobenzene, aniline and glycerol produce quinoline. The reaction takes place through several important stages. First, glycerol undergoes acid-catalysed dehydration. Concentrated sulphuric acid acts as a dehydrating agent and converts glycerol into acrolein. The reaction can be represented as: HOCH₂–CHOH–CH₂OH → CH₂=CH–CHO + 2H₂O Thus, glycerol generates acrolein, which is an α,β-unsaturated aldehyde. The formation of acrolein is a key step because it supplies the