3.9 Carboxylic acids and derivatives

Question 1

What is a carboxylic acid functional group

Answer 1

-COOH
C=O and C-OH

Question 2

How do you name carboxylic acids

Answer 2

-oic acid

Question 3

Are carboxylic acids soluble in water?
Why?
What influences their solublility

Answer 3

Yes
Acid group can form hydrogen bonds with water molecules

Question 4

What are the imfs in carboxylic acids

Answer 4

Hydrogen bonds - very strong

Question 5

What are esters (what are they formed from)
Func group
General formula

Answer 5

Formed from carboxylic acids and alcohols
RCOOR’ (C=O, C-O-C)

Question 6

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

Answer 6

CH3COOH + CH3CH2CH2OH –> CH3COOHCH2CH2CH3 + H2O

Question 7

How do you name esters

Answer 7

Start with the group that has replaced the hydrogen, then the acid part eg propyl (from alcohol) ethanoate (from carboxylic acid)

Question 8

What characteristic physical properties do esters have

Answer 8

Volatile
Pleasant fruit smells eg pear drops

Question 9

What are some uses of esters

Answer 9

Flavourings, perfumes, solvents, plasticisers

Question 10

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

Answer 10

CH3COOH(aq) <–> CH3COO-(aq) + H+(aq)

Question 11

How could you distinguish carboxylic acids from other -OH containing compounds

Answer 11

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

Question 12

Write an equation for the reaction of ethanoic acid with NaOH

Answer 12

CH3COOH + NaOH –> H2O + CH3COO-Na+

Question 13

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

Answer 13

Concentrated strong acid eg H2SO4

Question 14

What catalyst is needed for the hydrolysis of esters

Answer 14

Dilute strong acid eg H2SO4

Question 15

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

Answer 15

Glycerol / propane-1,2,3-triol

Question 16

What are the products of hydrolysing fats and oils

Answer 16

Glycerol and sodium salts of the acids that make up the ester

Question 17

What are the uses of glycerol and sodium salts

Answer 17

Soaps and cleaning products

Question 18

Common uses of glycerol

Answer 18

Solvent in many medicines
Solvent in food industry eg food colourings
Plasticising

Question 19

How do you make biodiesel (general equation and conditions)

Answer 19

NaOH catalyst
60 degrees C
Lipids + 3CH3OH –> 3 methyl esters + glycerol

Question 20

What does transesterification meam

Answer 20

Converting one type of ester to another

Question 21

What is a problem with producing biodiesel

Answer 21

Crops that could be used to make food are being used to make fuel

Question 22

What are carboxylic acid derivatives

Answer 22

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

Question 23

Name 2 acid derivatives and give their functional groups

Answer 23

Acyl chlorides: RCOCl
Acid anyhdrides: RCOOCR / (RCO)2O

Question 24

Are acyl chlorides or acid anhydrides more reactive

Answer 24

Acyl chlorides

Question 25

What is the name of the mechanism by which acyl chlorides and acid anhydrides acylate nucleophiles

Answer 25

Addition-elimination

Question 26

Draw the mechanism for the reaction of ethanoyl chloride and ammonia

Answer 26

Google

Question 27

Draw the mechanism for the reaction of ethanoyl chloride and methylamine

Answer 27

Google

Question 28

Draw the mechanism for the reaction of ethanoyl chloride and ethanol

Answer 28

Google

Question 29

Draw the mechanism for the reaction of ethanoyl chloride and water

Answer 29

Google

Question 30

What is a commercially important acylation reaction

Answer 30

The manufacture of aspirin

Question 31

What are the advantages of using ethanoic anhydride as an acylating agent over ethanoyl chloride

Answer 31

It is cheaper, less corrosive and does not react as readily with water
It is safer, as ethanoic acid is produced, rather than HCl which is corrosive

Question 32

What would you observe in a mtp determination if the samples was not pure

Answer 32

Samples melts over a large range (more than 3 degrees C)
Sample’s melting point is below the accepted value due to impurities disrupting structure

Question 33

What conditions are needed to form methyl esters from an acid anhydride or acyl chloride

Answer 33

React with methanol and heat gently under reflux

Question 34

When purifying by recrystallisation, why is the minimum volume of hot solvent used

Answer 34

So that a saturated solution is created, so that as many crystals will fall out of solution as possible when it is cooled

Question 35

Why is the solution filtered hot when purifying by recrystallisation

Answer 35

To remove insoluble impurities and ensure that the crystals do not form in the filter paper

Question 36

Why is the solution cooled in an ice bath when purifying by recrystallisation

Answer 36

To ensure that as many crystals as possible fall out of solution - higher yield

Question 37

Why are the crystals washed with cold water when purifying by recrystallisation

Answer 37

To remove soluble impurities

Question 38

How would you separate the crystals from the reaction mixture when purifying by recrystallisation

Answer 38

Filter under reduced pressure using a Buchner funnel