Steam Distillation
Experiment 2: Isolation of Eugenol from Cloves
Background; Readings on Vapor pressure, Raoult’s Law from TRO: A mixture of the essential oils, eugenol and acetyleugenol, will be steam distilled from cloves. These compounds are isolated from aqueous distillate by extraction into dichloromethane. The dichloromethane solution is shaken with aqueous sodium hydroxide, which will react with eugenol, to yield the sodium salt of eugenol in the basic aqueous layer, and acetyleugenol in the organic layer. The basic aqueous layer can be acidified to re-extract eugenol from it. And the organic layer can be dried and concentrated to yield acetyleugenol The principle of steam distillation is based on the fact that two immiscible liquids will boil at a lower temperature than the boiling points of either pure component, because the total vapor pressure of the heterogeneous mixture is simply the sum of the vapor pressures of the individual components (i. e. PT = PoA + PoB, where Po is the vapor pressure of the pure liquids). This leads to a higher vapor pressure for the mixture than would be predicted for a solution using Raoult’s Law(applies for miscible mixtures) (that is PT = Po(A)n(A) + Po(B)n(B), where n is the mole fraction of the component in the mixture). The higher total vapor pressure leads to a lower boiling point for the mixture than for either single component. The boiling point of eugenol, an oil found in cloves, is 248 °C, but it can be isolated at a lower temperature by performing a co-distillation with water. Steam distillation allows separating substances at lower temperatures which is useful since many organic compounds tend to decompose at high temperatures which regular distillation would require. For steam distillation to be successful, the material to be isolated must be insoluble in water. Usually these compounds have a low vapour pressure. After mixing them with
Background; Readings on Vapor pressure, Raoult’s Law from TRO: A mixture of the essential oils, eugenol and acetyleugenol, will be steam distilled from cloves. These compounds are isolated from aqueous distillate by extraction into dichloromethane. The dichloromethane solution is shaken with aqueous sodium hydroxide, which will react with eugenol, to yield the sodium salt of eugenol in the basic aqueous layer, and acetyleugenol in the organic layer. The basic aqueous layer can be acidified to re-extract eugenol from it. And the organic layer can be dried and concentrated to yield acetyleugenol The principle of steam distillation is based on the fact that two immiscible liquids will boil at a lower temperature than the boiling points of either pure component, because the total vapor pressure of the heterogeneous mixture is simply the sum of the vapor pressures of the individual components (i. e. PT = PoA + PoB, where Po is the vapor pressure of the pure liquids). This leads to a higher vapor pressure for the mixture than would be predicted for a solution using Raoult’s Law(applies for miscible mixtures) (that is PT = Po(A)n(A) + Po(B)n(B), where n is the mole fraction of the component in the mixture). The higher total vapor pressure leads to a lower boiling point for the mixture than for either single component. The boiling point of eugenol, an oil found in cloves, is 248 °C, but it can be isolated at a lower temperature by performing a co-distillation with water. Steam distillation allows separating substances at lower temperatures which is useful since many organic compounds tend to decompose at high temperatures which regular distillation would require. For steam distillation to be successful, the material to be isolated must be insoluble in water. Usually these compounds have a low vapour pressure. After mixing them with