Lesson 4: Bio Fuels and D-Limonene

About D-Limonene

  • unsaturated hydrocarbon with 2 carbon-carbon double bonds
  • chemical formula C10H16
  • has anti carcinogenic properties
  • used in numerous cleansing products
  • can be used as fuel
  • has aromatic properties

About Steam Distillation

  • oldest form of essential oil extraction
  • process does not denature structure of essential oil molecules
  • hot steam opens pockets in which the oils are kept and release the aromatic molecules from the fruit peels
  • molecules of these volatile oils then escape from the fruit peels and vaporise before condensing

Procedure

  1. Using a grater, grind only the coloured part of the peel of 4 medium-sized oranges into a beaker. Record the total mass of the grated orange rind. Image
  2. Add about between 50 and 150 mL of distilled water to the orange rind and transfer the mixture to a 250mL round-bottom flask.
  3. Set up the distillation apparatus as shown below. Image
  4. When the thermometer reads 50 degree Celsius, turn on the condenser water. The distillate containing D-Limonene will be collected in the conical flask
  5. Collect about 40mL of distillate before switching off the hot plate
  6. Transfer the distillate to a boiling tube and place it in the water bath for about 5 minutesImage
  7. When the boiling tube is removed from the water bath, 2 layers of liquid can be seen. The top layer is the product, limonene. There will also be a very strong smell of orange that can be smelt.

Note: A solution contaning D-limonene will decolourise bromine water because it is an alkene! 

Image

Concept behind Experiment

  • When water is added, D-limonene dissolves in it
  • During distillation, the water evaporates/boils, thus carrying the D-limonene molecules along with it
  • The water condenses and so does the D-limonene, which is collected in the distillate, giving rise to the aroma
  • D-limonene is less dense and hydrophobic, hence, it floats above the layer of water
  • To obtain greater purity, one should add less water and heat the solution slower

Calculations:

Mass of orange peels: 75.72 g

Amount of distillate obtained: 39.7 g

%yield=(75.72/39.7) x 100% = 52.4%

Unable to calculate purity because we did not take volume of essential oil we extracted. However, since purity and yield are inversely proportionate to each other, considering that we obtained such a high yield compared to the other groups, plus the fact that the aromatic scent our extracted D-limonene gave off was not as strong, we concluded that we did not obtain a high percentage purity of D-limonene.

Interesting Fact!

Limonene is a chiral molecule with two optical isomers (enantiomers). The major biological form d-limonene, the (R)-enantiomer, is used in food manufacture and medicines. It is also used as a fragrance in cleaning products, a botanical insecticide, and due to its flammability, a potential biofuel.
The (S)-enantiomer, l-limonene, is also used as a fragrance but has a piney, turpentine odour.

Sources:

http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/000/770/cfns%20experiment%2011%20-%20extracting%20limonene%20from%20oranges%20by%20steam%20distillation.pdf

Photo taken from:

http://www.reading.ac.uk/web/FILES/chemistry/Limonene.pdf

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