Esters Flashcards
When is an ester formed?
when an alcohol reacts with a carboxylic acid
other than an ester, What else is produced when an alcohol and carboxylic acid is produced?
Water
H from hydroxyl in alcohol and -OH from carboxyl in acid
What is the functional group of an ester?
ester link
O
II
-C-O-
How do you name an ester?
1st part from alcohol: -yl
eg ethyl
2nd part from carboxylic acid: -oate
eg methanoate
This would make ethyl methanoate
What reaction occurs when making esters?
A condensation reaction and this is reversible
Uses of esters?
-food flavourings
-fragrances (perfumes) (as many have a pleasant, fruity smell)
-solvents for non-polar compounds that do not dissolve in water
How do you make an ester?
1
-5 drops of concentrated sulfuric acid
-1cm3 carboxylic acid/1 small spatula
-1cm3 alcohol
2
-cotton wool
-wet paper (held with an elastic band)
-hot water bath
3
-pour contents of boiling tube
-20cm3 of base (sodium hydrogen carbonate),1spatula in 20cm3 of water—>to neutralise excess acid
-ester layer—>distinctive smell, 2 layers formed
why is cotton wool used when making esters?
so reactants don’t spurt out
Why is a wet paper towel used when making esters?
to act as a condenser
(to condense vapors –turn them into liquids – by cooling them down.)
why is are is the boiling tube put in a water bath and not a bunsen burner when making esters?
as reactants/alcohol are flammable
What is ester hydrolysis?
alkaline hydrolysis
the splitting of an ester into alcohol and caboxylic acid
ester + water <—>alcohol + carboxylic acid
sodium hydroxide (alkali) is added as a catalyst
reversible reaction/equilibrium (in closed system) is established
fats/oil + water —>glycerol + fatty acid
proteins + water—>amino acid
Alkaline hydrolysis set-up (check with jotter)
Reflux set-up
water outlet
condenser
water inlet
round bottom flask
reactants (ester+sodium hydroxide)
anti-bumping granules
heating mantle
When propyl propanoate and water added in water hydrolysis, what is made in steps 1 and 2
1
propyl propanoate + water <—> propanol + sodium propanoate (salt)
NAOH also added
2
sodium propanoate + hydrochloric acid —> propanoic acid
what is the catalyst used in the formation of esters
concentrated sulfuric acid
What is a condensation reaction?
-an addition reaction where water is made as a by-product
-2 molecules joining together with a loss of a water molecule
the formation of an ester from alcohol and carboxylic acid using concentrated sulfuric acid as a catalyst
