Esters Flashcards
what is the functional group of an esther?
-COO-
what are esters?
organic compounds formed by the reaction of an alcohol with a carboxylic acid
draw the functional group of an Ester?
-C-O-
II
O
how is ethyl ethanoate formed?
it is produced when ethanol and ethanoic acid react in the presence of an acid catalyst
write out the equation for making an ester
(the -> is reversable and the conditions are heat and concentrated sulphuric acid)
what are the conditions required for esterification?
concentrated suphuric acid catalyst, heat
what happens when an ester is made? what type of reaction is it? what is this called?
this is called esterification. It is also a condensation reaction because water is made when two molcules are joined together. it is also a reversible reaction
why is esterification a reversible reaction?
it is reversible so to maximise the yield of ethyl ethanoate we use pure ethanol and ethanoic acid.
what is pure ethanoic acid also called?
glacial ethanoic acid
how do you name esters?
the alcohol goes first and the acid goes second
e.g., ethanoic acid + propan-1-ol -> propyl ethanoate
how do you write the displayed formula of ethyl ethanoate?
how do you write the structural formula of ethyl ethanoate?
CH3COOCH2CH3
what is important to keep in mind when writing out and drawing out esters
structural adn displayed formula
in the structural formula, you always write out the ethanoate part out first and then the alcohol part. therefore, it is also easier to draw out the displayed formula in the same way so as to not get confused.
reminder: the name of the ester goes alcohol-carboxylic acid so it is a bit counterintuitive
what type of compounds are esters? where are esters used?
volatile compounds (likely to change suddenly and unexpectedly-evaporate quickly) with distinctive smells and are used as food flavourings and perfumes
where are esters most ususally used in
- small esters are used in solvents (most commonly)
- food flavourings
- perfumes
- strong smells e.g., bananas, pears, other fruit
describe a practical where you would prepare a sample of an ester such as ethyl ethanoate
- set up a hot water bath using a kettle and a 250 mL beaker half filled with boiling water. (with builing waber)
- Put 10 drops of pentan-1-ol in a boiling tube and add 10 drops of concentrated ethanoic acid. (or 1cm3).
- Mix well.
- Your teacher will carefully, add a few drops of concentrated sulphuric acid using a teat pipette using a fume cupboard. Note that the teat pipette should be stored upright in a test tube in a test tube rack to avoid the outside of the pipette becoming coated in acid. Wear gloves.
- Warm the boiling tube in the hot water (80 degrees) bath for 5 minutes.
- allow contents to cool
- Pour the contents of the boiling tube into 50 cm3 of sodium carbonate solution (0.5 mol/dm3) in a beaker and smell cautiously following the method shown to you by your teacher. Do not smell before carrying out this step. (waft the smell, dont put nose above beaker)
- a layer of ester will separate to float on the top of the water and the acid will mostly dissolve in the water but the ester won’t. this makes them easier to smell.
- Repeat the experiment to make other esters using the correct acid and alcohol. If using a solid acid, use a small spatula full (0.2g approx.)
describe a practical where you would prepare a sample of an ester such as ethyl ethanoate
- set up a hot water bath using a kettle and a 250 mL beaker half filled with boiling water. (with builing waber)
- Put 10 drops of pentan-1-ol in a boiling tube and add 10 drops of concentrated ethanoic acid. (or 1cm3).
- Mix well.
- Your teacher will carefully, add a few drops of concentrated sulphuric acid using a teat pipette using a fume cupboard. Note that the teat pipette should be stored upright in a test tube in a test tube rack to avoid the outside of the pipette becoming coated in acid. Wear gloves.
- Warm the boiling tube in the hot water (80 degrees) bath for 5 minutes.
- allow contents to cool
- Pour the contents of the boiling tube into 50 cm3 of sodium carbonate solution (0.5 mol/dm3) in a beaker and smell cautiously following the method shown to you by your teacher. Do not smell before carrying out this step. (waft the smell, dont put nose above beaker)
- a layer of ester will separate to float on the top of the water and the acid will mostly dissolve in the water but the ester won’t. this makes them easier to smell.
- Repeat the experiment to make other esters using the correct acid and alcohol. If using a solid acid, use a small spatula full (0.2g approx.)
what would a practical where you would prepare a sample of an ester such as ethyl ethanoate look like if you drew it out?
draw out ethyl propanoate
draw out methyl ethanoate
draw out propyl mthanoate
when making the ester, why is the reaction mixture poures into the sodium carbonate solution?
to neutralise the acid catalyst and quench the reaction
