Question

a. Why can steam distillation be an effective method to separate 2 compounds?

b. What conditions must be met for steam distillation to be useful?

Answer 1

Steam distillation is a special type of distillation (a separation process) for temperature sensitive materials like natural aromatic compounds Many organic compounds tend to decompose at high sustained temperatures. Separation by distillation at the normal (1 atmosphere) boiling points is not an option, so water or steam is introduced into the distillation apparatus. The water vapor carries small amounts of the vaporized compounds to the condensation flask, where the condensed liquid phase separates, allowing for easy collection. This process effectively allows for distillation at lower temperatures, reducing the deterioration of the desired products. If the substances to be distilled are very sensitive to heat, steam distillation may be applied under reduced pressure, thereby reducing the operating temperature further.

After distillation the vapors are condensed. Usually the immediate product is a two-phase system of water and the organic distillate, allowing for separation of the components by decantation, partitioning or other suitable methods.

. For example, the boiling point of bromobenzene is 156 °C and the boiling point of water is 100 °C, but a mixture of the two boils at 95 °C. Thus, bromobenzene can be easily distilled at a temperature 61 °C below its normal boiling point. Because of this reason steam distillation is effective method .

B)The process becomes more useful when the substance is high boiling and decomes near normal boiling point for eg iodobenzene with boiling point at 461K can be made to boil at 371.2 by steam distillation.