Carboxylic acids and esters

Question 1

What is the general formula of a carboxylic acid?

Answer 1

COOH

Question 2

How do you name carboxylic acids?

Answer 2

-oic acid.

Question 3

Are carboxylic acids soluble in water? Why?

Answer 3

Yes - the acid group forms hydrogen bonds with water molecules.

Question 4

What are the intermolecular forces in carboxylic acids?

Answer 4

Hydrogen bonds.

Question 5

What are esters formed from?

Answer 5

Carboxylic acids and alcohols.

Question 6

What is the functional group of on ester?

Answer 6

COO-

Question 7

What is the general formula of an ester?

Answer 7

RCOOR’

Question 8

Write an equation for the reaction of ethanoic acid with propan-1-ol.

Answer 8

CH3COOH + CH3CH2CH2OH → CH3COOCH2CH2CH3 + H2O

Question 9

How do you name esters?

Answer 9

Start is from alcohol, end is from carboxylic acid.

Question 10

What physical properties do esters have?

Answer 10

*volatile
*pleasant fruity smell

Question 11

What are some uses of esters?

Answer 11

*flavourings
*perfumes
*solvents
*plasticisers

Question 12

What are some common natural esters?

Answer 12

Fats and oils.

Question 13

Draw a diagram showing the way a carboxylic acid is polarised.

Answer 13

…

Question 14

Write an equation for the equilibrium formed by ethanoic acid in solution.

Answer 14

CH3COOH (aq) ⇌ CH3COO- (aq) + H+ (aq)

Question 15

What happens to the negative charge on the ethanoate ion in terms of electrons?

Answer 15

Electrons delocalise so the negative charge is shared across the whole of the carboxylate group.

Question 16

How would you distinguish between carboxylic acids and other compounds containing -OH?

Answer 16

Add NaHCO3 - acids will produce sodium, salt, water and carbon dioxide.

Question 17

Write an equation for the reaction of ethanoic acid with NaOH.

Answer 17

CH3COOH + NaOH → H2O + CH3COO-Na+

Question 18

Write an equation for the reaction of ethanoic acid with Na2CO3.

Answer 18

2CH3COOH + Na2CO3 → 2CH3COO-Na+ + CO2

Question 19

What catalyst is needed for the formation of esters from alcohols and carboxylic acids?

Answer 19

Concentrated strong acid (e.g. H2SO4).

Question 20

What catalyst is needed for the hydrolysis of esters?

Answer 20

Dilute strong acid.

Question 21

What is an alternative method of hydrolysis?

Answer 21

Base hydrolysis.

Question 22

What are the advantages of base hydrolysis?

Answer 22

Reaction goes to completion due to neutralisation by the base - more product in the mixture than acid-catalysed hydrolysis.

Question 23

Which alcohol forms the esters that make up animal and vegetable oils?

Answer 23

Glycerol/propane-1,2,3-triol

Question 24

What is the difference between oil and fat?

Answer 24

*at room temp, oils are liquid, fats are solid
*fats are saturated, oils are not

Question 25

What are the products of hydrolysing fats and oils?

Answer 25

Propane-1,2,3-triol and sodium salts of the acids that make up the ester.

Question 26

What are the uses of the products of hydrolysis of fats and oils?

Answer 26

Soaps and cleaning products.

Question 27

What does the long hydrocarbon chain of the carboxylate ion do?

Answer 27

Mixes with grease.

Question 28

What does the COO- group do?

Answer 28

Mixes with water.

Question 29

How does the carboxylate ion with a long carbon chain make a good cleaning agent?

Answer 29

Means that grease can be removed from water.

Question 30

What is the systematic name of glycerol?

Answer 30

Propane-1,2,3-triol.

Question 31

What are some common uses of glycerol?

Answer 31

*pharmaceutical and cosmetic preparations *solvent in medicines (toothpaste) *solvent in food industry (food colouring) *plasticising various material (sheets, gaskets, cellophane, paper)

Question 32

What is the equation for making biodiesel?

Answer 32

lipids + 3CH3OH → 3 methylesters + glycerol

Question 33

What are the conditions for making biodiesel?

Answer 33

*NaOH catalyst *60°C

Question 34

What is transesterification?

Answer 34

Converting one type of ester to another.

Question 35

What kind of crops is biodiesel made from?

Answer 35

*rapeseed oil *soybean oil

Question 36

How is the reaction mixture of biodiesel purified and separated?

Answer 36

*settling tank/centrifuge *remove remainder with water *add acid to neutralise excess alkali catalyst *solid soap is formed (easy to remove)

Question 37

What is a problem with producing biodiesel?

Answer 37

Is is using crops that could be used for food.

Question 38

What are carboxylic acid derivatives?

Answer 38

Molecules that have the acyl group as part of their structure, formed from carboxylic acids.