Organic Chemistry - Heterocyclic Compounds - Pyridine PDF

Organic Chemistry Heterocyclic Compounds Pyridine | Lec.12 Pyridine Contents : Conversion of acid chlorides into acid derivatives 3 Pyridine Conversion of acid chlorides into acid derivatives : In the laboratory, amides and esters are usually prepared from the acid chloride rather than from the acid...

Organic Chemistry Heterocyclic Compounds Pyridine | Lec.12 Pyridine Contents : Conversion of acid chlorides into acid derivatives 3 Pyridine Conversion of acid chlorides into acid derivatives : In the laboratory, amides and esters are usually prepared from the acid chloride rather than from the acid itself. Both the preparation of the acid chloride and its reactions with ammonia (amine) or an alcohol are rapid, essentially irreversible reactions. It is more convenient to carry out these two steps than the single slow, reversible reaction with the acid (direct esterification or direct amide formation). Pyridine For example: c Pyridine Aromatic acid chlorides (ArCOCl) are considerably less reactive than the aliphatic acid chlorides. With cold water, for example, acetyl chloride reacts almost explosively, whereas Benzoyl chloride reacts only very slowly. The reaction of aromatic acid chlorides with an alcohol or a phenol is often carried out using the Schotten-Baumann technique: The acid chloride is added in portions (followed by vigorous shaking) to a mixture of the hydroxy compound and a base, usually aqueous sodium hydroxide or pyridine (an organic base ). Pyridine Although the function of the base is not clear, it seems not only to neutralize the hydrogen chloride that would otherwise be liberated, but also to catalyze the reaction: Pyridine