Esters Flashcards
How are esters formed?
Esters are formed by the condensation reaction between a carboxylic acid and an alcohol.
When producing an ester what is the function of the ‘wet paper towel’ condesner?
To prevent reactants and products escaping from the reaction vessel in vapour form.
When producing an ester why was concentrated sulfuric acid used?
It acts as a catalyst.
Why is a water bath used instead of a Bunsen burner when producing a ester?
Some of the reactants and products are flammable.
What is the purpose of the sodium hydrogen carbonate solution?
To neutralise the concentrated sulfuric acid and any unreacted carboxylic acid.
Give two suggestions seen when a ester has been formed?
There is an oily layer on the surface and there is a distinctive smell.
What is the ester link shown as in molecular formulae?
-COO-
What is hydrolysis?
To split a compound by adding water.
What can hydrolysis be used for in esters?
The parent carboxylic acid and alcohol can be obtained.
What is distillation?
Distillation is a process to separate the alcohol from the reaction mixture.
What are fats and oils?
Fats and oils are triglycerides and edible fats and oils are esters.
What functional group do they contain?
An ester link.
What does the hydrolysis of fats and oils produce?
Fatty acids and glycerol in the ratio of three fatty acids to one glycerol.
What is glycerol known as?
Trihydric alcohol and propan-1,2,3-triol.
How are fatty acids and oils formed?
By the condensation of glycerol and three carboxylic acid molecules.
What is the structural difference between unsaturated and saturated fatty acids?
Unsaturated contains a double carbon to carbon bond and there is a kink in the chain.
How can you tell if a fatty acid is unsaturated, monounsaturated or poly unsaturated?
Substitute an H for the COOH group. Recognise which it is
Alkane CnH2n+2 - Saturated
Alkene CnH2n - Poly or mono unsaturated
Note: If it is poly, it will not fit the alkene or alkane formulas and will have less hydrogens.
What is the difference between fats and oils?
Fats are solid at room temperature and oils are liquids at room temperature.
What is the lower melting point of oil related to?
The degree of unsaturation in the oil molecule.
describe why oils have a lower melting point than fats.
The greater the degree of unsaturation, the lower the melting point.
Explain fully why oils have a lower melting point than fats.
Double bonds in the fatty acid chains prevent oil molecules from packing closely together, so the greater the number of double bonds present, the weaker the London dispersion forces of attraction.
Note: fats don’t or do always have double bonds.
What test could be done to determine the degree of unsaturation?
Unsaturated compounds quickly decolourise bromine solution.
How can vegetable oils form margarine?
Can be hydrogenated using a nickel catalyst.
What is hydrogenation?
The addition of hydrogen across a carbon do carbon bond.
