CD.7 Flashcards
The structure of triglyceride molecules
What is the difference between fats and oils?
Fats are solid at room temperature, whereas oils are liquid.
What type of chemical are fats and oils?
Esters.
What two type of chemicals are reacted together to make esters of fats and oils?
Pronpane-1,2,3-triol and long-chain carboxylic acids.
What is propane-1,2,3-triol more commonly known as?
Glycerol.
How many carboxylic acid molecules can form ester linkages with each glycerol molecule?
3, because glycerol has three alcohol groups.
As each glycerol can form three ester links, what is the ester product called?
Triester.
What is a triester also known as?
Triglyceride.
Do all three acid groups have to be the same in a triester?
No, in natural oils and fats the three acid groups are often different.
Why is it that fats and oils don’t mix well with water?
The presence of long non-polar acid chains mean they don’t mix well with water as it can’t break up the strong hydrogen boning between water molecules.
What are long chain carboxylic acids also known as?
Fatty acids.
What are some properties of carboxylic acid residues in fats and oils?
- They usually have unbranched hydrocarbon chains.
- They usually contain an even number of carbon atoms of up to 24. The most common ones contain 16 or 18 carbon atoms.
- They can be saturated or unsatured (contains double bonds).
What two properties of fats and oils can be explained by the structure of the long carboxylic acid residue chains?
- Hydrophobic, it doesn’t mix with water.
- Melting point difference between fats and oils.
What feature of the carboxylic acid residues explains the low melting point of oils?
A high degree of unsaturation the carboxylic acid chain. This is because double bonds disrupts the linear zigzag structure of the chain resulting in less intermolecular forces.
What process is used to break fats or oils into glycerol and fatty acids so it can be identified?
Hydrolysis.
How do can you hydrolyse fats or oils?
Heat the fat or oil with concentrated sodium hydroxide to give glycerol and the sodium salt of the fatty acids. Then you should add hydrochloric acid to get the fatty acids and sodium chloride.
