Intermediate Topic 860 of 1102 Organic Chemistry
Purification of Organic Compounds
Distillation, crystallization, sublimation and chromatography isolate pure compounds.
In-depth explanation of Purification of Organic Compounds
Purification removes impurities from an organic compound so that its properties can be measured reliably. Solids are commonly purified by recrystallization, in which the compound is dissolved in hot solvent and crystallizes on cooling, and by sublimation for volatile solids. Liquids are purified by distillation, including simple, fractional, vacuum and steam distillation, and by solvent extraction. Mixtures are separated by chromatography. Purity is confirmed by a sharp melting point or boiling point and by thin-layer chromatography.
Going deeper: Purification of Organic Compounds
Key ideas: Method depends on the type of impurity: crystallisation for solids (solubility low when cold), sublimation for solids with high vapour pressure (naphthalene, camphor), simple distillation if boiling points differ by over 40 degrees, fractional distillation for closer ones, steam distillation for liquids immiscible with water and decomposing at their boiling point, vacuum distillation for high boiling or heat sensitive liquids, and differential extraction for solutes in water.
Common mistakes and connections: Students use simple distillation for close-boiling mixtures. Another error is believing steam distillation works for any liquid: it needs immiscibility with water. Purity is verified by sharp melting point (a range of 1 to 2 degrees) or constant boiling point. Links to chromatography, intermolecular forces and vapour pressure.
Visualization of Purification of Organic Compounds
Recrystallization works because solubility of benzoic acid rises steeply with temperature, so pure crystals form as the hot solution cools. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Benzoic acid is purified by recrystallization from hot water, since it is much more soluble in hot water than in cold.
Frequently asked questions about Purification of Organic Compounds
What is Purification of Organic Compounds?
Distillation, crystallization, sublimation and chromatography isolate pure compounds.
Is Purification of Organic Compounds a beginner, intermediate or advanced topic?
Purification of Organic Compounds is a intermediate topic in Organic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Purification of Organic Compounds?
Study these earlier topics in Organic Chemistry first: Petrochemicals, Qualitative Organic Tests, Iodoform Reaction.
What comes after Purification of Organic Compounds?
The next topics in Organic Chemistry are Chromatography and Elemental Analysis.
Can I practise Purification of Organic Compounds with quizzes?
Yes. The interactive lesson includes a self-check question on Purification of Organic Compounds, and the Organic Chemistry quiz draws on every topic in this area.
Where Purification of Organic Compounds fits in Organic Chemistry
Purification of Organic Compounds is topic 132 of 148 in Organic Chemistry.