TAE: Esterification Flashcards
What is a functional group?
A functional group is a group of atoms attached to a carbon compound which determines its chemical properties. It is the site in the carbon compound where chemical reaction takes place.
Describe the differences between the alkanol and alkanoic acid functional groups in carbon compounds
The functional group of alkanols is the hydroxyl group (-OH).
The functional group of alkanoic acids is the carboxylic acid group (-COOH).
– This group is acidic as it can dissociate to form ions in solution and behave as a weak acid.
Explain the difference in melting point and boiling point caused by straight-chained alkanoic acid and straight-chained primary alkanol structures
Alkanols have hydrogen bonding between the O in one molecule and the H of an-OH in a nearby molecule.
- A H-bonding is very strong, a lot of energy is required to break them
- Hence alkanols have a high M.P. and B.P.
The -COOH group of alkanoic acids has the ability to be involved in two hydrogen bonds (as opposed to only one in alkanols).
- Also, as alkanoic acids have greater molar masses than their corresponding alkanols, there are more random movements of electrons and hence they have greater dispersion forces.
- This means even more energy is required to break apart molecules of alkanoic acids thank alkanols.
Hence, alkanoic acids have a higher M.P. and B.P. than alkanols
What is esterification?
Esterification is the reaction of an alkanoic acid with an alkanol to produce an alkyl alkanoate
(ester).
It is a slow endothermic reaction that does not go to completion.
alkanoic acid + alkanol <> alkyl alkanoate (ester) + water
Describe the purpose of using acid in esterification for catalysis
Concentrated sulfuric acid is used as a catalyst, and a dehydrating agent to increase yield by absorbing the product water to favour the toward reaction, shifting equilibrium to the right.
What is refluxing?
Refluxing is the process of heating a liquid mixture with a condenser attached vertically above the reaction vessel, in order to prevent the loss of volatile reactants or products.
Why is refluxing needed?
Refluxing is required because the esterification process is endothermic and hence requires heating to be efficient.
Esterification is a slow process, so heat is required to increase the rate of reaction.
A condenser is used to avoid loss of material from the reaction vessel, as cool water circulates to cool the vapours which condense back into liquid and fall back into the reaction mixture.
Outline some examples of the occurrence, production and uses of esters
– Flavourings: due to their pleasant, fruity
odours (e.g. pineapple - butyl butanoate; apple – ethyl pentanoate).
Solvents: Domestic uses of esters include ethyl ethanoate for nail polish remover and scents
for perfumes.
– Emulsifiers: Esters (e.g. glycerol) that have high molecular weight are used as emulsifying
agents to prevent oils and water separating into layers in cosmetics and food products.
