2b. Esters, Fats, Oils, Soaps, detergents and Emulsifiers Flashcards
What is the functional group in esters?
The ester link
Which 2 homologous series react together to form esters?
Alcohols and carboxylic acids
What are the properties of a common ester (pentyl ethanoate)?
What are the 3 main uses for esters?
What type of reaction is undergone when an ester is formed?
A condensation reaction
What are sources of fats and oils
What category of compounds are fats and oils?
They are esters
Why are fats and oils sometimes called tri-esters?
Because they have 3 carboxylate (ester link) groups in each molecule
What is the parent alkanol in all fats and oils?
Glycerol
(Propan-1, 2, 3 triol)
What is the structure of glycerol?
What is meant by a fatty acid?
A long chain carboxylic acid with a 16 or 18 carbon chain
What is the ratio of fatty acid to glycerol molecules when a fat or oil is made?
3:1
What are the differences between fats and oils?
What is meant by an “unsaturated” molecule?
A molecule with at least 1 C=C bond present
Testing fats and oils for levels of unsaturation
Also see video on google classroom
What effect does unsaturation have on the shape of tri-esters?
What effect does the irregular shape of unsaturated “tuning fork” have on how the molecules pack together?
How could the levels of unsaturation in oils / fats be tested?
Bromine (or Iodine) will add across the C=C bond and decolourise as it does so.
A clear end point will be shown when the decolourising stops.
The more C=C bonds there are, the higher the volume of Br2 or I2 it will take to reach end point
Tri-esters are also known as what (based on glycerol name)
Tri-glycerides
Why are some oils hydrogenated?
To make them have higher melting points and be more stable.
What are the 6 points needed to be covered to explain difference in melting points of fats and oils?
- Level of unsaturation (C=C bonds)
- Effect this has on tuning fork shape
- Effect this has on how close they can pack together
- Effect this has on intermoleular (LDF) attractions
- Level of energy need to break them
- corresponding lower or higher melting point
What happens to fats and oils when they react with oxygen?
They become rancid
What is meant by “hydrolysis”?
The breaking down of a molecule using the chemical action of water
Which molecule is ALWAYS produced when fats and oils are hydrolysed?
Glycerol
What catalyst is used in reaction mixture?
Concentrated sulphuric acid
Why is a water bath used to heat mixture?
Alkanols are flammable
What is purpose of small test tube?
Acts as a condenser
What are the reactants to make esters?
Carboxylic acids and alkanols
What type of reaction is esterification?
Condensation
Given that esters and carboxylic acids are isomers, how could we distinguish between them?
- pH indicator; acids -red; esters stay green
- electrical conductivity; only acids would conduct.
- solubility (miscibility) in water; only acids would be soluble (miscible)
- reaction with Mg. Only acids would react to release hydrogen.
- smell: esters would (mostly) have a sweet smell where acids would be sour or sharp
