Carboxylic acids and Esters

Question 1

Physical properties of carboxylic acids which determine their melting points

Answer 1

Every carboxylic acid has a different melting point
1. OH Bond forms hydrogen bonding which has a high melting point and boiling point compared to similar size alkanes.
2. The oxygen in carboxylic acids are polar whereas the hydrocarbon chain of a carboxylic acid is nonpolar so doesn’t dissolve in water.
A shorter carboxylic acid is more soluble than a longer carboxylic acid as the hydrocarbon chain part of the molecule is longer even though the COOH dissolves well this is cancelled out by the Insolublility of the chain

Question 2

Formula of esters

Answer 2

RCOOR

Question 3

Naming esters

Answer 3

1. Name but with C=O
2. Then men the alkyl group after the C-O

Question 4

Forming esters

Answer 4

Formed from alcohols and carboxylic acids
1. Remove H of alcohol
2. Remove OH from carboxylic acid
3. H2O is a by product
4. Reversible reaction
5. H2SO4 catalyst used
Called a condensation reaction

Question 5

Hydrolysis of esters (2 ways )

Answer 5

1. Opposite of condensation reaction
   H2SO4 catalyst
   Add OH back onto carboxylic acid
   Add H onto alcohol
   Addition of H2O

Question 6

2nd way of hydrolysis of esters

Answer 6

Base catalysed hydrolysis
+ H2O
Use of NaOH catalyst
1. Form carboxylic acid and alcohol from H2O
2. Carboxylic acid converted into salt from ONa to form eg sodium ethanoate and alcohol

Question 7

Use of ester

Answer 7

Fats and oils
Such as tryglerides which are made from fatty and and glycerol which is a tri ester and is written as propane 1,2,3 triol with a carboxylic acid ( fatty acid )

Question 8

Forming tri ester

Answer 8

Glycerol and carbolic acid = tri ester and H2O

Question 9

Hydrolysis of tri ester (2 ways )

Answer 9

Tri ester + 3 H2O = carboxylic acid and alcohol in presence of acid catalyst and reflux

Question 10

Base hydrolysis of esters

Answer 10

Use of 3H2O to form glycerol and fatty acid then use of 3NaOH to form salt eg sodium ethanoate

Question 11

Use of salt

Answer 11

Soap

Question 12

Biodiesel

Answer 12

Tri ester with 3 CH2OH and NaOH catalyst to form glycerol and biodiesel with CH3O attached to carboxylic acid

Question 13

Acyl chloride formula

Answer 13

RCOCl

Question 14

Acid anhydride naming

Answer 14

CH3COOCH3 = ethonoic anhydride as same number of c on either side
If not same then alphabetical order eg
CH3COOCH2CH3 = Ehanoic propanoic anhydride

Question 15

Acyl chloride mechanisms
Name 4 nucleophiles

Answer 15

1. H2O
2. Alcohols
3. NH3
4. Amines eg RNH2

Question 16

Name of mechanism with Acyl chloride

Answer 16

Nucleophilic addition elimination

Question 17

Acyl chloride with water

Answer 17

Carboxylic acid and HCl

Question 18

Acyl chloride with alcohol

Answer 18

Ester and HCl

Question 19

Acyl chloride with ammonia

Answer 19

Amide ( NH2) + NH4Cl

Question 20

Acyl chloride with amine

Answer 20

N- substituted amide and RNH3Cl

Question 21

Naming amides

Answer 21

CH3CONH2
Ethanamide

Question 22

Naming N - substituted amines

Answer 22

Put N -
Look at alkyl group attached to N
Name the rest but add amide
Eg CH3COONHCH3CH
N-ethyl ethanamide

Question 23

Key points of mechanism

Answer 23

Question 24

Mechanisms with acid anyhydride

Answer 24

Either side molecule leaves
So can form more than one way of product

Question 25

Industrial use

Answer 25

Acid anhydride reactions used more than Acyl Chlorides as
1. Cheaper
2. No HcL fumes so not corrosive
3. Don’t react with H2O