ORGANIC cHEMISTRY - Iv

Experiment 5

Aim of the Experiment

Isolation of natural products using steam distillation. (Essential Oils from Spices: Oil of Cloves or Cinnamon)

Principle

The technique of steam distillation allows the separation of volatile components from non-volatile materials without the need for raising the temperature of the distillation above 100 ^oC. It provides a method for the isolation of natural products such as essential oils, which tend to be prone to decomposition at elevated temperatures. Essential oils are volatile compounds responsible for the aromas commonly associated with many plants.

Application of steam distillation can be found in the production of consumer food products and petroleum industries. They are used in separation of fatty acids from mixtures.

Materials required

conical flasks, distillation assembly, condenser, adapters, heating mantle, sample of natural product etc.

Procedure

Assemble an apparatus using the 10-mL round bottom vial, a Hickman head, and a water cooled reflux condenser. Adjust the temperature of the sand bath initially to about 130 ^oC. During the distillation, you should be able to increase the sand bath temperature to about 150 ^oC, as frothing becomes less of a problem.

Place about 0.30-g of natural product (record actual weight) of ground cloves into the round bottom vial and add 4.0-mL of water and a boiling stone.

Begin heating the mixture to provide a steady rate of distillation. The temperature of the mixture can be controlled by raising or lowering the round bottom vial in the sand. You may also push the sand towards the flask with a spatula when a higher temperature is needed, or the temperature of the sand may be increased. With cinnamon, it is essential to control the temperature so that the boiling mixture does not rise above the neck of the Hickman head. While being careful, remember that in order to complete the distillation in a reasonable length of time, you will have to boil the mixture as rapidly as possible without allowing it to splash into the Hickman head. The distillation with cloves can be done with more vigorous boiling. However, some care must be exercised to ensure that the mixture doesn't froth too much.

To perform the following operations, it will be necessary to temporarily remove the reflux condenser. During the distillation, replace the water lost through distillation by adding fresh hot water to the boiling mixture using a Pasteur pipet which is passed through the Hickman head into the roundbottom vial. As the distillation proceeds, collect the distillate with a second Pasteur pipet and use it to rinse the walls of the Hickman head at 5-10 minute intervals. As the distillate continues to collect in the reservoir of the Hickman head, use the Pasteur pipet to transfer it to a 5-mL conical vial. The rinsing and transferring operations are best accomplished if the Pasteur pipet is bent slightly at the end.

If you are distilling oil of cloves, continue the steam distillation with frequent rinsing of the Hickman head and collection of the distillate in the 5-mL conical vial until you have obtained 2.5-mL of distillate, then proceed to the next paragraph. If you are distilling cinnamon, continue the steam distillation until you have collected about 1.5-mL of distillate. Raise the assembly and allow the roundbottom vial to cool until you can touch it with your fingers. Remove the flask and discard the mixture of ground cinnamon and water, but save the stirring bar. It is not necessary to clean the roundbottom vial or the Hickman head at this stage. Add 0.50-g of fresh cinnamon (record actual weight), 6.0-mL of water, and return the magnetic stirring bar to the flask. Reassemble the apparatus and continue the distillation. Rinse the Hickman head as before and transfer the distillate to the same 5-mL conical vial. When you have collected another 1.5-mL of distillate (for a total of 3.0-mL), the distillation may be stopped and you may proceed to the next paragraph.

The essential oil will now be extracted with dichloromethane. Cap the vial securely and shake it vigorously with frequent venting. Allow the layers to separate. Using a filter-tip pipet, transfer the lower (dichloromethane) layer to a second dry 5-mL conical vial. Repeat this procedure with two more 1.0-mL portions of dichloromethane, combining all the extracts into the same 5-mL conical vial. If there are visible drops of water in the vial, it will be necessary to transfer the dichloromethane solution with a dry pipet into another dry conical vial. combined the organic extracts and dry over sodium sulphate.

Remove the dichloromethane by leaving the vial in the hood until the solvent has evaporated and nothing but an oily residue remains. Alternatively, you may evaporate the dichloromethane in the hood with a gentle stream of dry air while heating the conical vial in a warm (40-50 ^oC) sand bath. Tap the vial with your finger to provide agitation in order to facilitate removal of the remaining solvent.

When the solvent has been removed, weigh the conical vial. Calculate the weight percentage recovery of the oil from the original amount of spice used

Calculation

Weight of the product = ________________________(Y) g

Result

1. Weight of the product = _____________________ g

2. % Yield of the product = _____________________

3. Melting Point (M.P.) of the product = ______________________°C

Reference Material

Demo videos for steam distillation

www.youtube.com/watch?v=bmK9m2MLI4w

www.youtube.com/watch?v=IC0qYhQ2XNg&t=327s

Questions

1. Principle of steam distillation?

2. Various types of distillation and their applications?