DeanStarkmenetelmä

The Dean-Stark apparatus is a laboratory glassware setup used in organic chemistry to remove water from a reaction mixture by azeotropic distillation. It consists of a distillation flask, a condenser, and a graduated trap. The trap is designed to collect the condensed distillate, allowing the water to separate and be measured, while the organic solvent, which is typically less dense than water, overflows and returns to the distillation flask.

This method is particularly useful for reactions that produce water as a byproduct, such as esterifications, acetal formations, and dehydrations. By continuously removing water, the equilibrium of these reversible reactions is shifted towards product formation, thereby increasing the yield. The apparatus works by heating the reaction mixture, causing the solvent and water to vaporize. These vapors rise into the condenser, where they are cooled and liquefied. The liquid then flows into the Dean-Stark trap. Because water is generally immiscible with common organic solvents used in these reactions and is also denser, it settles at the bottom of the trap, while the lighter organic solvent collects above it and is siphoned back into the distillation flask. The amount of water collected in the trap can be monitored, providing an indication of the reaction's progress. Common solvents used with a Dean-Stark apparatus include toluene, xylene, and benzene.