Organic Chemistry – Some Basic Principles and Techniques

Chemistry · Class 11

Simulation · Chemistry · Class 11

Steam distillation boils below 100 °C

From the lesson Methods of purification in Organic Chemistry – Some Basic Principles and Techniques. Change the values and watch what happens.

Steam distillation boils below 100 °CChemistry · Class 11

The idea behind it

NCERT § "Methods of Purification of Organic Compounds"

  • Sublimation separates a solid that passes directly into vapour on heating from non-sublimable impurities.
  • Crystallisation relies on the compound being much more soluble in a hot solvent than in the cold one; impurities stay in solution. Repeated crystallisation removes impurities of similar solubility.
  • Simple distillation separates liquids with large boiling point differences, or a volatile liquid from non-volatile impurities.
  • Fractional distillation uses a fractionating column to separate liquids whose boiling points are close; it is used to separate crude oil fractions.
  • Distillation under reduced pressure lets liquids that decompose at or below their normal boiling point boil at a lower temperature; glycerol is recovered from spent-lye this way in soap manufacture.
  • Steam distillation purifies substances that are volatile in steam and immiscible with water, such as aniline; the mixture boils when the sum of the vapour pressures of water and the compound equals atmospheric pressure, below 373 K.
  • Differential extraction shakes an aqueous solution with an organic solvent in which the compound is more soluble and which does not mix with water; the layers are separated in a separating funnel.
  • Chromatography separates components by their different affinities for a stationary phase and a moving (mobile) phase.
  • Adsorption chromatography uses a solid adsorbent such as silica gel or alumina, in column chromatography or thin layer chromatography (TLC); partition chromatography, as in paper chromatography, uses water held in the paper as the stationary phase.
  • Retardation factor Rf = distance moved by the substance from the baseline / distance moved by the solvent front; colourless spots are located under UV light, with iodine vapour or with a reagent such as ninhydrin for amino acids.