Extraction of the Essential Oil Limonene from Oranges

Extraction of the Essential Oil Limonene from Oranges.

Chemistry Department Outreach Team.

Ahmed Saleh, Denefield school, Reading 2008

The Distillation

Steam Distillation of Orange Peel Low molecular weight water immiscible compounds can be separated from natural products by steam distillation. In this case steam distillation is used to isolate the essential oil limonene from the orange peel.

Extraction of Limonene from the Distillate

Initially an oily water / limonene mixture can be seen condensing on the glassware at a distillation temperature of 98 C. The temperature will rise to 100oC as the distillate composition approaches pure water.

The lower layer is the remaining aqueous distillate

Limonene is concentrated in the peel of an orange. The orange peel has two distinct layers, the skin and the pith. Limonene Is not distributed evenly between these two layers. Experimentation has shown that only minimal quantities of limonene can be extracted from the white pith.

Pith Skin

Mass of Orange Peel

Limonene’s structure

This outer skin accounts for two – thirds of the mass of the peel. The best yields of limonene are obtained by using only this outer skin.

The yield of limonene is about 1% using this outer skin. This is a large yield compared to other essential oil extractions, where yields can range from 1-0.01 % by mass.

Orange peel cut into small pieces, placed into 100 mL of water

Evaporation of the Solvent

Limonene can be observed as an oily suspension in the final distillate (80 mL).

Heat

Essential oils can be steam distilled from flowers, leaves, fruits, barks and woods Essential oils are found in many household products, ranging from high end cosmetics to basic cleaning materials.

Lavender

Patchouli

Limonene, an alkene, is extracted into a low density water immiscible solvent (ether).

Bergamot

Cinnamon

To finalise the extraction, the ether layer (b.pt. 37oC) was evaporated on a water bath to leave the limonene (b.pt. 176oC). limonene (150mg) obtained from 15 g of orange peel skin. The limonene has an intense aroma of oranges