Question

what is the advantage of codistilling cloves with water as opposed to distilling without water for the steam distillation of eugenol?

Answer 1

The boiling point of clove oil(eugenol) is 248 °C, therefore it can be isolated at a lower temperature by performing a co-distillation with water, this process is also known as a steam distillation results in the degradation of eugenol, so steam distillation can be performed at a temperature slightly less than 100 °C. Since eugenol is not soluble in water,it forms a suspension. The vapor pressure of water at 100 °C is 760 torr, and the vapor pressure of eugenol at 100 °C is approximately 4 torr; therefore, the vapor is roughly 0.5 % eugenol. Generally suspension boils when it’s vapor pressure is equal to the external pressure. Since both the eugenol and the water are contributing to the vapor pressure of the suspension, the suspension will boil before either pure substance would normally boil.

After the steam distillation, the distillate will contain both water and eugenol, the eugenol is extracted from the water using an organic solvent. The pure form eugenol is finally isolated by evaporation of the organic solvent.