2.4 Esters, fats and oils Flashcards
Ester
An ester is a molecule containing an ester link: ─COO─.
How are esters named?
- names of their parent alcohol and carboxylic acid
- structural formulae of esters formed from primary, straight-chain alcohols containing no more than eight carbons and straight-chain carboxylic acids containing no more than eight carbons
Use of esters
Esters are used as flavourings and fragrances as many have pleasant, fruity smells. Esters
are also used as solvents for non-polar compounds that do not dissolve in water.
How are esters formed?
by a condensation reaction between an alcohol and carboxylic acid
What is a condensation reaction?
two molecules joined together with the elimination of a small molecule
What small molecule is eliminated when an ester is formed?
Water
Hydrolysis of an ester
produces an alcohol and carboxylic acid
What is a hydrolysis reaction ?
a molecule reacts with water to break down into smaller molecules
How are edible fats and oils formed?
Edible fats and oils are esters formed from the condensation reaction of glycerol (propane-1,2,3-triol) and 3 carboxylic acid molecules.
The carboxylic acids are known as ‘fatty acids’ and can be saturated or unsaturated straight-chain carboxylic acids
Edible oils and fats melting points
Edible oils have lower melting points than edible fats.
Double bonds in fatty acid chains prevent oil molecules from packing closely together, so the greater the number of double bonds present, the weaker the van der Waals forces.
Greater degree of unsaturation, the lower the mpt
How does bromine solution indicate presence of double bonds?
Unsaturated compounds quickly decolourise bromine solution.
The bromine molecules add across the carbon-carbon double bonds in an addition reaction. The greater the number of double bonds present in a substance, the more bromine solution can be decolourised
Fats and oils are:
- a concentrated source of energy
- essential for the transport and storage of fat-soluble vitamins in the body
