Esters

Question 1

When is an ester formed?

Answer 1

when an alcohol reacts with a carboxylic acid

Question 2

other than an ester, What else is produced when an alcohol and carboxylic acid is produced?

Answer 2

Water

H from hydroxyl in alcohol and -OH from carboxyl in acid

Question 3

What is the functional group of an ester?

Answer 3

ester link
O
II
-C-O-

Question 4

How do you name an ester?

Answer 4

1st part from alcohol: -yl
eg ethyl

2nd part from carboxylic acid: -oate
eg methanoate

This would make ethyl methanoate

Question 5

What reaction occurs when making esters?

Answer 5

A condensation reaction and this is reversible

Question 6

Uses of esters?

Answer 6

-food flavourings
-fragrances (perfumes) (as many have a pleasant, fruity smell)
-solvents for non-polar compounds that do not dissolve in water

Question 7

How do you make an ester?

Answer 7

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

Question 8

why is cotton wool used when making esters?

Answer 8

so reactants don’t spurt out

Question 9

Why is a wet paper towel used when making esters?

Answer 9

to act as a condenser
(to condense vapors –turn them into liquids – by cooling them down.)

Question 10

why is are is the boiling tube put in a water bath and not a bunsen burner when making esters?

Answer 10

as reactants/alcohol are flammable

Question 11

What is ester hydrolysis?

Answer 11

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

Question 12

Alkaline hydrolysis set-up (check with jotter)

Answer 12

Reflux set-up

water outlet
condenser
water inlet
round bottom flask
reactants (ester+sodium hydroxide)
anti-bumping granules
heating mantle

Question 13

When propyl propanoate and water added in water hydrolysis, what is made in steps 1 and 2

Answer 13

1
propyl propanoate + water <—> propanol + sodium propanoate (salt)

NAOH also added

2
sodium propanoate + hydrochloric acid —> propanoic acid

Question 14

what is the catalyst used in the formation of esters

Answer 14

concentrated sulfuric acid

Question 15

What is a condensation reaction?

Answer 15

-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

Question 16

2 observations that show you have produced an ester

Answer 16

-distinctive fruity scent
-2 layers (insoluble ester layer)

Question 17

Are esters polar or non-polar?

Answer 17

non-polar (not soluble in water)

Question 18

are alcohols, carboxylic acids, and amino acids polar or non-polar?

Answer 18

polar (soluble in water)