Carboxylic acids and esters

Question 1

Solubility of carboxylic acids?

Answer 1

• COOH group = soluble due to H bonding
• hydrocarbon chain = non-polar
• short chain carboxylic acids = soluble
• long chain carboxylic acids = insoluble

Question 2

Why do carboxylic acids act as acids?

Answer 2

They donate a proton

Question 3

Carboxylic acids are weak acids. What does this mean?

Answer 3

Equilibrium lies to the left

Question 4

How is an ester formed?

Answer 4

Carboxylic acid + alcohol

Question 5

What catalyst is used in esterification?

Answer 5

H2SO4

Question 6

3 facts about esterification reactions.

Answer 6

• Water is always a product
• Reversible reaction
• catalyst is H2SO4

Question 7

What is the name of the reaction that allows esters to be turned back into carboxylic acids and alcohols?

Answer 7

Hydrolysis reaction

Question 8

What is meant by hydrolysis?

Answer 8

Breaking of a bond using water

Question 9

What are the two types of hydrolysis?

Answer 9

• Acid catalysed hydrolysis
• Base catalysed hydrolysis

Question 10

Acid hydrolysis of propylethanoate?

Answer 10

propylethanoate + water —> propan-1-ol + ethanoic acid
catalyst = H2SO4

Question 11

What is an example of an acid catalyst?

Answer 11

HCl

Question 12

What is an example of base catalyst?

Answer 12

Warm, aqueous NaOH

Question 13

In which type of hydrolysis results in high yield of product?

Answer 13

Base hydrolysis

Question 14

Base hydrolysis of propylethanoate?

Answer 14

propylethanoate + water —> propan-1-ol + ethanoic acid
ethnic acid + NaOH —> Sodium ethanoate
catalyst - NaOH

Question 15

What is the IUPAC name for glycerol?

Answer 15

propane-1,2,3-triol

Question 16

What is biodiesel?

Answer 16

Mixture of methyl esters

Question 17

Uses for esters?

Answer 17

• Plasticisers
• Perfumes
• Flavourings
• Solvents for many reactions

Question 18

What is an example of an acyl chloride?

Answer 18

ethanoyl chloride CH3COCl

Question 19

What is an example of an acid anhydride?

Answer 19

ethanoic anhydride

Question 20

Name CH3CH3COCl

Answer 20

propanoyl chloride

Question 21

Name CH3CH2CH2CH2CH2COCl

Answer 21

hexanoyl chloride

Question 22

What functional group is formed when an acyl chloride reacts with water?

Answer 22

Carboxylic acid

Question 23

What functional group is formed when an acyl chloride reacts with an alcohol?

Answer 23

Ester

Question 24

What functional group is formed when an acyl chloride reacts with ammonia?

Answer 24

Amide

Question 25

What functional group is formed when an acyl chloride reacts with an amine?

Answer 25

N-substituted amide

Question 26

suggest why aqueous ethanol is a suitable solvent when heating the coconut oil with KOH give a safety precaution when heating the mixture. justify choice

Answer 26

reason - allows to dissolve both oil and KOH safety precaution - use water bath for heating mixture justification - prevents risk of fire

Question 27

why are acylation with acid anhydrides more commonly used than acyl chlorides in industry

Answer 27

- cheaper - less corrosive - don't react with water - safer side product = carboxylic acid - acyl chloride produces HCl vapours

Question 28

describe briefly how you would determine melting point of aspirin

Answer 28

- Sample in capillary / melting point tube - Heat in melting point apparatus

Question 29

write equation for reaction between butendioic acid and NaOH

Answer 29

2NaOH + HO2CCHCHCO2H → NaO2CCHCHCO2Na + 2H2O

Question 30

suggest why only one of two E/Z isomers of butendioic acid can readily form acid anhydride when warmed

Answer 30

- both COOH groups must be on the same side - no rotation about C=C axis

Question 31

C = ester D = carboxylic acid identify reagent in test tube reaction to distinguish between C and D

Answer 31

reagent = NaHCO3 C observation = no observation D = effervescence

Question 32

explain why ethanol chloride can readily react with nucleophiles

Answer 32

- Large charge on carbonyl carbon atom due to bonding to O and Cl - Nucleophiles have electron pairs which can be donated

Question 33

one advantage using propanol chloride instead of propanoic acid in lab preparation of methyl propanoate from methanol

Answer 33

- faster/bigger yield/no acid catalyst required

Question 34

Suggest why an excess of sodium hydroxide is used.

Answer 34

to ensure ester reacts completely

Question 35

equation for reaction between sodium benzoate and hydrochloric acid

Answer 35

C6H5COONa + HCl → C6H5COOH + NaCl

Question 36

Suggest two reasons why, in an industrial situation, ethanoic anhydride would be preferred to ethanoyl chloride in the production of paracetamol.

Answer 36

Any two from: *        less exothermic reaction *        easier to control *        dangerous gas not evolved *        ethanoic anhydride is a cheaper or more easily recycled reagent.