Dean–Stark apparatus

A glassware assembly that separates and collects water during azeotropic distillation, commonly removing water from a reaction mixture.

Azeotropic distillation: A distillation method that uses an entrainer to alter vapor–liquid equilibrium and separate a mixture. An entrainer carries water into the apparatus, where condensed liquid separates into layers.
Fischer esterification: An acid-catalyzed reaction of a carboxylic acid with an alcohol that produces an ester and water. Removing the water can shift this reversible reaction toward ester formation.
Azeotrope: A liquid mixture that boils with vapor composition equal to its liquid composition at a given pressure. A water-carrying azeotrope enables water to leave the reaction mixture with solvent vapor.
Rotary evaporation: A reduced-pressure evaporation technique used to remove volatile solvents from liquid samples. Rotary evaporation concentrates mixtures after reaction; it does not selectively collect water during reflux.
Ernest Woodward Dean: An American chemist whose name is associated with the Dean–Stark apparatus. His surname forms the apparatus’s commonly used name.
Heterogeneous azeotrope: An azeotrope whose condensed liquid separates into two immiscible liquid phases. Two liquid phases let the trap return the organic layer while retaining water.
Imine formation: A condensation reaction between a primary amine and a carbonyl compound that forms a carbon–nitrogen double bond. Water removal can favor formation of the imine product.
Entrainer: A substance added to a mixture to alter its distillation behavior and assist separation. The chosen entrainer carries water overhead and must form a separable condensate.
Molecular sieve: A porous material with molecular-sized pores that adsorbs selected molecules, including water. Molecular sieves remove water by adsorption rather than azeotropic distillation and phase separation.
David Dewey Stark: An American chemist whose name is associated with the Dean–Stark apparatus. His surname forms the second part of the apparatus’s name.

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EsterificationRelated: It drives some esterifications forward by continuously removing the water formed.