This subtopic builds upon concepts introduced in Stage 1 subtopics 3.3 and 4.1.

Edible oils and fats are esters of propane-1,2,3-triol (glycerol) and various carboxylic acids.

• Draw the structural formula of an edible oil or fat, given the structural formula(e) of the carboxylic acid(s) from which it is derived.

Triglyceride formation animation

Triglycerides can be hydrolysed to produce propane-1,2,3-triol and various carboxylic acids.

• Identify and draw the structural formulae of the alcohol and acid(s) from which a triglyceride is derived, given its structural formula.

See above.

Triglycerides may be saturated or unsaturated.

• Describe and explain the use of a solution of bromine or iodine to determine the degree of unsaturation of a compound. Draw the structural formula of the reaction product.
• Explain how the degree of unsaturation causes differences in the melting points of edible oils and fats.

Video: Testing alkenes with bromine water

Unsaturation lab (scroll down for diagram)

Mind map with links

Liquid triglycerides can be converted into triglycerides of higher melting point.

• Explain the role of pressure, temperature, and a catalyst in the hydrogenation of liquid triglycerides to form triglycerides of higher melting point.

Additional information

Video: Documentary on margarines (not all relevant)

Alkaline hydrolysis of triglycerides produces carboxylate ions, which have both hydrophilic and hydrophobic regions.

• Explain how such particles form micelles in solutions.
• Explain how micelles can dissolve and move non-polar substances through an aqueous medium or vice versa.

Video: Soaps and detergents

Animated notes (page 1 only)