Organic | Carboxylic acids and derivatives

Question 1

3.3.9.1 Carboxylic acids and esters

Outline the structure of a carboxylic acid.

Answer 1

RCOOH

end with -oic acid

Question 2

3.3.9.1 Carboxylic acids and esters

Outline an example of the structure of a carboxylic acid.

Answer 2

CH3CH2COOH

Propanoic acid

Question 3

3.3.9.1 Carboxylic acids and esters

Outline an example where there a carboxylic acids at each end.

Answer 3

HOOCCOOH

ethanedioic acid.

Question 4

3.3.9.1 Carboxylic acids and esters

Describe the physical properties of a carboxylic acid.

Answer 4

1. can form H bonds with H2O molecules.
2. COOH up to 4C are soluble in H2O.
3. form H bonds with each other in solid state.
4. higher mp than alkanes.

Question 5

3.3.9.1 Carboxylic acids and esters

Describe the acidity of carboxylic acids.

Answer 5

Weak acids } will partially dissociate in H2O.
They will react with carbonates to form CO2.

Question 6

3.3.9.1 Carboxylic acids and esters

State why delocalisation occurs.

Answer 6

The carboxylic acids salts are stablised by delocalisation, making the dissociation more likely.

Question 7

3.3.9.1 Carboxylic acids and esters

Describe how a delocalised ion forms.

Answer 7

H3C-C=O-OH →delocalised →H3C-C-O-O

1. H on OH group is lost } carboxylate ion is formed.
2. Delocalised ion has equal C-O bond lengths.
3. Delocalisation makes ion more stable and more likely to form as the pi charge cloud is delocalised and has spread out.

Question 8

3.3.9.1 Carboxylic acids and esters

What would happen if delocalisation did not occur?

Answer 8

The C=O would be shorter than the C-O bond.

Question 9

3.3.9.1 Carboxylic acids and esters

What group is electron releasing?

Answer 9

Alkyl group.

Question 10

3.3.9.1 Carboxylic acids and esters

How are alkyl groups electron releasing?

Answer 10

H3C-CH2-COOH → delocalised →H3C-CH2-COO

1. Increase in chain length pushes e- denisty onto COO- ion.
2. more negative
3. less stable } acid less strong.

Question 11

3.3.9.1 Carboxylic acids and esters

What functional group is electron withdrawing?

Answer 11

Chlorine.

Question 12

3.3.9.1 Carboxylic acids and esters

How is Cl electron withdrawing?

Answer 12

H2ClC-COOH→deloc.→H2ClC-COO

1. EN- Cl atom withdraws electron density from COO- ion.
2. Less negative
3. More stable } acid is more strong.

Question 13

3.3.9.1 Carboxylic acids and esters

What is the inductive effect?

Answer 13

The pushing away or withdrawal of electrons.

Question 14

3.3.9.1 Carboxylic acids and esters

How can salts be formed using carboxylic acids?

Answer 14

COOH can form salts with metals, alkalis and carbonates.

Question 15

3.3.9.1 Carboxylic acids and esters

Acid + metal →

CH3COOH + Na →

Answer 15

salt + hydrogen

CH3COO-Na+ + H2

Question 16

3.3.9.1 Carboxylic acids and esters

Acid + Alkali (base)→
CH3COOH + NaOH →

Answer 16

Salt + water

CH3COO-Na+ + H2O

Question 17

3.3.9.1 Carboxylic acids and esters

Acid + carbonate →

2CH3COOH + CaCo3 →

Answer 17

Salt + water + Co₂

(CH3COO-)₂Ca+ + H₂O + CO₂

Question 18

3.3.9.1 Carboxylic acids and esters

How are esters formed?

Answer 18

COOH + alcohol ⇌ ester + H2O
in the prescence of an acid catalyst.

Question 19

3.3.9.1 Carboxylic acids and esters

Outline a generic example of the formation of esters.

Answer 19

R-COOH + R-OH ⇌ R-COO-R + H2O

Question 20

3.3.9.1 Carboxylic acids and esters

What is the general formula of esters?

Answer 20

RCOOR’

Question 21

3.3.9.1 Carboxylic acids and esters

How to name esters?

Answer 21

1st part: alcohol
2nd part: COOH
3rd part: remove “-oic acid” and add “-oate”

H3C-CH2-COO-CH2-CH3
ethyl propanoate

think of the OO in COO as zero so you must start counting from there for both the carboxylic part and alcohol part.

Question 22

3.3.9.1 Carboxylic acids and esters

What are the common uses of esters?

Answer 22

1. Perfumes and food flavouring } sweet-smelling, non-toxic and soluble in solvent.
2. Plasticiers } used for polymers, limited flexibility (pure polymer), adding plasticiers to polymer allows it to move easily, more flexible.
3. Solvents } polar, low bp (evapourate easily), insoluble in H2O.

Question 23

3.3.9.1 Carboxylic acids and esters

In what conditions can esters be hydrolysed in?

Answer 23

Acid
Alkaline

Question 24

3.3.9.1 Carboxylic acids and esters

What does the hydrolysis of esters form?

Answer 24

Ester + water ⇌ COOH + alcohol

Question 25

3.3.9.1 Carboxylic acids and esters

Outline the reagent, conditions and simple equation using CH3COOCH3 as the ester in acidic conditons.

Answer 25

Reagent:
dilute HCl or H2SO4

Conditions:
heat under reflux

Simple equation:
CH3COOCH3 + H2O ⇌ CH3COOH + CH3OH
in prescence of acid catalyst (reagent).

Question 26

3.3.9.1 Carboxylic acids and esters

Outline the reagent, conditions and simple equation using CH3COOCH3 as the ester in alkaline conditons.

Answer 26

Reagent:
dilute NaOH

Conditions:
heat under reflux

Simple equation:
CH3COOCH3 + NaOH → CH3COO-Na+ + CH3OH

COOH salt is the product of the anion of COOH.
The anion is resistant to attack by weak nucleophiles (OH), making the reaction NOT reversible.

Question 27

3.3.9.1 Carboxylic acids and esters

Will the CH3COO-Na+ be affected by the addition of HCl, if yes how?

Answer 27

Yes, as it will convert the salt into a COOH.

CH3COO-Na+ + HCl →CH3COOH + NaCl