Question

In an Organic Chemistry Lab entitled: Natural Product Isolation: Isolation of Eugenol from Oil of Cloves

a.) What would happen if the NaOH solution was replaced with deionized water inthe first step of the extraction procedures?

b.) How would the experiment be different if you used dichloromethane instead ofdiethyl ether as the organic solvent?

c.) Why did the solution turn cloudy when you added the 3M HCl?

Thanks for the help.

Answer 1

a)

The clove oil is yellow colored and it contains a mixture of various components most of which is eugenol .

The structure of eugenol is given below.

From the above structure, we can see that eugenol contains phenolic group. Phenols are water insoluble. In order to extract eugenol from the clove oil, we have to selectively dissolve it. Phenols are soluble in bases. And therefore, when a base like NaOH is added to clove oil, eugenol can react with it forming a water soluble sodium salt shown below.

This salt forms the aqueous layer which can be separated from the rest of the organic mixture.

Therefore purpose of adding NaOH in the first step of extraction is to dissolve eugenol

If we use deionized water instead of NaOH, we would not be able to extract eugenol to aqueous layer and cannot continue the extraction process further

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b)

The density of dichloromethane is 1.33 g/ mL whereas that of diethyl ether is0.713 g/mL. If we compare both these values to that of water, we can say that dichloromethane is heavier than water and diethyl ether is lighter than water.

Therefore when we use dichloromethane as the organic solvent for extraction, the aqueous layer containing eugenol will float on top of the water. When we add dichloromethane to aqueous layer, eugenol will get extracted to organic layer which will be on the bottom of the separating funnel. So we can simply drain the lower layer into a separate flask. And continue the extraction by adding more dichloromethane.

We don't have to collect both layers into separate flasks as we did in the extraction with diethyl ether.

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c)

When we add NaOH in the first extraction step, we convert eugenol to its sodium salt which is water soluble. And therefore we were able to extract eugenol to aqueous layer.

When we add 3 M HCl to this aqueous layer, HCl reacts with this sodium salt regenerating eugenol. Since eugenol is insoluble in aqueous layer, the whole solution turns cloudy giving it an appearance of an emulsion/

The reaction is shown below.