Unit 2 : Esters Flashcards
What is the ester link
O
||
—C—O
What are the properties of an ester
- Clear, colourless liquid
- Sweet, pleasant - “pear drops”
- Immiscible in water - separate layers
- PH=7 (neutral)
- Dissolves many non polar and polar substances
How do you name esters
Part that attaches to the single bonded oxygen comes from the alcohol, the part attached to the carbon is from the carboxylic acid
Converting parent alcohols to ester “Christian name”
Methanol —> methyl
Ethanol —> ethyl
Propanol —> propyl
Butanol —> butyl
Converting the parent acid to ester “surname”
Methanoic —> methanoate
Ethanoic —> ethanoate
Propanoic —> propanoate
butanoic —> butanoate
What are the uses of esters
- They are used as artificial flavourings
- They are used in fragrances such as apples and bananas
- They are used for non polar industrial solvents
How are esters formed
Esters are formed from a condensation reaction between an alcohol and a carboxylic acid
What is a condensation reaction
A condensation reaction is when 2 molecules join together with the loss of a small molecule (usually water)
How to make esters in a lab
- Reaction mixture contains alcohol and a carboxylic acid
- Concentrated sulphuric acid is added, it acts like a catalyst
- A water bath is used instead of a Bunsen burner as Alkanols are flammable
- The mixture is heated to increase reaction rate
- A paper towel is used as a condenser to prevent vapours from leaving the rest tube
- The mixture is then added to sodium hydrogen carbonate solution to react with any excess acid.
What are the signs an ester has been produced
- An immiscible layer forms on surface
* A sweet/solventy smell is noticed
What is hydrolysis of an ester
- Hydrolysis is the breaking apart of a compound using the chemical action of water
- Hydrolysis of an ester will give back the parent alcohol and alkanoic acid
