Cloves contain two principal essential oils, caryophyllene and eugenol. A student carrying out a steam distillation using cloves obtained a mixture of these two oils in the distillate. Explain how the student could separate and isolate the two essential oils using liquid-liquid extraction (hint: phenols are moderately acidic and can be deprotonated by NaOH).
Take the hint. Eugenol is a phenol and the other one is a hydrocarbon; add NaOH to make the Na salt and it will be soluble in water whereas the caryophyllene will more than likley be soluble in ether or some other non-polar solvent. Extract with the two liquids. The Na salt of the eugenol will stay in the water, the other compound will go with the non-polar solvent.
To separate and isolate the two essential oils, caryophyllene and eugenol, from the distillate using liquid-liquid extraction, the student can follow these steps:
1. Start by adding an equal volume of a water-immiscible organic solvent (such as diethyl ether or dichloromethane) to the distillate containing the mixture of the two oils.
2. Close the container and vigorously shake the mixture to ensure thorough mixing of the organic solvent and the distillate. This step allows the essential oils to dissolve in the organic solvent phase.
3. After allowing the mixture to settle, two distinct layers will form: the organic phase (containing the essential oils) and the aqueous phase. At this point, the student can carefully separate the two layers without mixing them.
4. Transfer the organic solvent phase (containing the essential oils) to a separate container, leaving the aqueous layer behind. This can be done using a separating funnel or a pipette if the layers are clear and well-defined.
5. Next, the student needs to convert the eugenol into its phenolate form by deprotonation using a strong base, such as sodium hydroxide (NaOH). To do this, slowly add a concentrated NaOH solution to the organic solvent phase containing the mixture of essential oils. The NaOH will react with the eugenol to form sodium eugenolate.
Since eugenol is moderately acidic, it can be deprotonated by the hydroxide ions from NaOH, resulting in the formation of sodium eugenolate.
6. Once the NaOH solution is added, the mixture should be gently shaken or stirred to allow for complete reaction between eugenol and NaOH. This step ensures that the eugenol is converted to its phenolate form.
7. After the reaction is complete, allow the mixture to settle, and two layers will form again: the organic phase (now containing only caryophyllene) and the aqueous phase (containing sodium eugenolate).
8. Carefully separate the two layers, as done before, and transfer the organic phase (containing caryophyllene) to a clean, dry container. The aqueous phase (containing sodium eugenolate) can be discarded.
9. To regenerate eugenol from its phenolate form, add a strong acid, such as hydrochloric acid (HCl), to the organic phase. The acid will neutralize the sodium eugenolate, converting it back into eugenol.
10. Allow the mixture to settle once more, and two distinct layers will form: the organic phase (containing regenerated eugenol) and the aqueous phase (containing the neutralized acid).
11. Separate the two layers, as done previously, and transfer the organic phase (containing regenerated eugenol) to a clean, dry container. The aqueous phase (containing the neutralized acid) can be discarded.
Now the student has successfully separated and isolated the two essential oils, caryophyllene and eugenol, using liquid-liquid extraction.
To separate and isolate the two essential oils, caryophyllene and eugenol, using liquid-liquid extraction, the student can follow these steps:
1. Start with the mixture of essential oils obtained from steam distillation.
2. Add a strong base, such as sodium hydroxide (NaOH), to the mixture. The purpose of adding the base is to deprotonate the phenolic compound, eugenol, which is moderately acidic.
3. By deprotonating eugenol with NaOH, it will form a water-soluble salt called sodium eugenolate.
4. Caryophyllene, being non-polar, will remain in the organic layer while sodium eugenolate will dissolve in the aqueous layer.
5. Now, the student can perform a liquid-liquid extraction by separating the two layers. This can be done by using a separatory funnel or a separating funnel, where the layers can be easily separated due to their density difference.
6. Collect the organic layer (containing caryophyllene) separately in a clean container.
7. The aqueous layer, which contains sodium eugenolate, can be acidified by adding a strong acid, such as hydrochloric acid (HCl), to convert sodium eugenolate back into eugenol.
8. Once the eugenol is regenerated in the organic layer, the student can repeat the liquid-liquid extraction process by separating the two layers using the separatory funnel.
9. Collect the organic layer again and remove any remaining traces of acid or water by using anhydrous sodium sulfate or other suitable drying agents.
10. Finally, the student can obtain pure caryophyllene and eugenol by evaporating the solvent from the organic layer. This can be done by using a rotary evaporator or by simply allowing the solvent to evaporate at a controlled temperature and low pressure.
It is important to note that liquid-liquid extraction is just one method to separate and isolate the essential oils. There are other techniques like column chromatography, fractional distillation, or vacuum distillation that can be used depending on the specific properties of the compounds involved.