Question

Scenario: You are working in an industrial process laboratory and you are using pyridine in your synthetic reaction. After several attempts, you cannot get your reaction to work. You suspect that your labmate has contaminated your pyridine with aniline, a reagent they commonly work with.

Explain how you can separate the mixture of pyridine and aniline to re-isolate pure pyridine. Include relevant physical data and the literature reference to support your explanation.

Answer 1

The boiling point of aniline is 184.1^oC and the boiling point of pyridine is 115.2^oC. The difference in the boiling point of aniline and pyridine allows to separate them from the mixture using fractional distillation.

Fractional distillation is a technique which can be used to separate the components of the mixture based on their boiling point difference. The component with lower boiling will evaporate first, the vapors of which are then condensed and collected in a flask and as the temperature of the liquid rises beyond the boiling point of the other liquid component it also vaporizes and the vapors of which are collected by condensing the vapors in a separate flask.