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1. EXPERIMENT 5 Steam Distillation

2. Steam Distillation : Objectives 2 To calculate the mass ratio of two immiscible liquids collected by co-distillation . To extract Eugenol oil from Cloves seeds

3. Distillation types Simple distillation Fractional d istillation steam distillation Steam Distillation : Introduction M iscible liquids ( homogeneous mixture ) miscible liquids always results in a boiling point for the mixture between the separate liquids I mmiscible liquids ( heterogeneous mixture ) I mmiscible liquids always results in a lower boiling point for the mixture than for the separate liquids . Purification of liquids Volatile compounds immiscible with water can be purified by co-distillation T he mixture will boil at constant temperature less than the boiling point of any of them. 3

4. Steam Distillation : Introduction The components of an immiscible mixture boil at lower temperatures than the boiling point of any of the components. Thus, a mixture of high-boiling organic compounds (higher than 100 °C) and water can be distilled at a temperature less than 100 ºC , the boiling point of water. Natural products, such as flavourings and perfumes from leaves and flowers, are sometimes separated from their sources by steam distillation . This technique is also used occasionally in the organic laboratory in lieu of vacuum distillation or other separation techniques. The principle that gives rise to steam distillation is that the total vapor pressure of a mixture of immiscible liquids is equal to the sum of the vapor pressures of the pure individual components. Steam distillation is used in the purification of compounds with very high boiling points and in the isolation of volatile compounds from plants. When a small amount of material is to be separated from a large bulk of solid, this makes ordinary distillation, filtration, and extraction difficult or impractical, Thus, steam distillation is often used. 4

5. Steam Distillation : Introduction 5

6. Steam Distillation : Introduction In steam distillation of a mixture of X and Y the ratio of the vapor pressure of X to Y should equal to the molar ratio of X to Y in the mixture as shown in the following equation: T he relative weights of the two liquids which are collected in the receiver (gas components) are directly proportional to both: the vapor pressure of the liquids at the distillation temperature the molecular weights of the liquids 6 PV=NRT

7. Steam Distillation : Introduction The result means bromobenzene will distil 1.6 times as fast as water 7

8. Steam Distillation : Introduction Examples of using steam distillation in the isolation of natural product 1) Isolation of citrus oil from orange peels 8

9. Steam Distillation : Introduction Examples of using steam distillation in the isolation of natural product 1) isolation of oil of cloves numb the pain of a tooth ache Eugenol oil ( cloves oil); dental pain killers Oil of cloves is rich in eugenol (4-allyl-2-methoxyphenol) and contains a trace amount of caryophyllen 9

10. Steam Distillation : Practical part 1) S team distillation for a mixture of bromobenzene and water 1. Assemble simple distillation apparatus 2. Add to distillation flask 3 mL water and 15 ml bromobenzene . 3. Steam distils the mixture using a Bunsen burner collecting 30 mL of co-distillate in a 100 mL graduated cylinder. 4. Determine the volume of the bromobenzene and the volume of the water layers; use the density of bromobenzene and water to convert the volume into weight. 5. Determine the experimental ratio of bromobenzene to water in the distillate. 6. Use the vapor pressures of water and bromobenzene given in the example determine the theoretical ration of bromobenzene to water in the distillate. 7. Compare the results and record your conclusion in the report 10

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12. Steam Distillation : Practical part 2) Extraction of essential oil from cloves seed 1. Wight about 20 g of cloves . Transfer the cloves to a 500 mL distillation flask. 2. Add to 300 mL water to the Flask . 3. Set up a simple distillation apparatus. 4. Steam distil the mixture using a Bunsen Burner collecting 70 mL of distillate 5. Transfer the distillate from the graduated cylinder to a separatory funnel. 6. Add to it about 30 mL of saturated NaCl solution .(salt-out effect ) 7. Extract the flask aqueous layer in the separatory funnel with dichloromethane (2 X 10 mL). 8. Combine the dichloromethane layers in a 100 mL Erlenmeyer flask, add to it two spoons of drying agent Na 2 SO 4 . 9. Decant the dichloromethane to a pre-weighed a 100 mL dry and clean beaker . 10. Evaporate the dichloromethane on a hot plate in the hood. 11. The residue is cloves oil, determine the weight of the cloves oil 12. Calculate the % of cloves oil. ( % cloves oil = (mass of cloves oil / 20 g) X 100) 12

13. Steam Distillation : Practical part 2) Extraction of essential oil from cloves seed https://www.youtube.com/watch?v=BnUiLAfMQhU 13

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