Question

The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in vapour phase. A suitable method for the extraction of these oils from the flowers is -

• A. crystallisation
• B. distillation under reduced pressure
• C. distillation
• D. steam distillation

Answer 1

The Correct Option is D

The query concerns the optimal technique for obtaining essential oils from floral sources. Essential oils are steam-volatile organic compounds, largely immiscible with water at ambient temperatures, yet capable of coexisting with water vapor in the gaseous state. Let us evaluate the provided options:

• Crystallisation: Primarily employed for purifying solid compounds; unsuitable for volatile liquids like essential oils.
• Distillation under reduced pressure: Also termed vacuum distillation, it facilitates distillation at lower temperatures for heat-sensitive substances. While beneficial for temperature-susceptible compounds, it is not the definitive method for substances that readily combine with steam.
• Distillation: Standard distillation involves heating to separate volatile components. This is a general technique for readily vaporized substances. Essential oils necessitate specialized conditions due to their affinity for steam.
• Steam distillation: This method is specifically designed for extracting volatile compounds from non-volatile matrices. It operates by passing steam through the plant material, vaporizing the essential oils concurrently with the steam, followed by condensation and separation.

Considering the characteristics of essential oils—their volatility with steam and miscibility with water vapor—steam distillation emerges as the most suitable methodology. This process enables oil vaporization at reduced temperatures, thus safeguarding their delicate composition and fragrance.

Consequently, the correct selection is steam distillation.