Carboxylic acids and derivitives

Question 1

what is the suffix for carboxylic acids

Answer 1

-oic acid

can be en or an

Question 2

what is the carboxylic acid functional group

Answer 2

COOH

Question 3

describe the solubility of carboxylic acids

Answer 3

Carboxylic acids are more soluble in water than their equivilent aldehyde or alcohol because they can form multiple hydrogen bonds with water.

via the H in their OH and from the lone pairs of e⁻ from their =O

Question 4

state and explain the trend in solubility along the homologuous series

Answer 4

water solubility decreases as the number of carbon atoms in the chain increases as hydrocarbons can only form london forces not hydrogen bonds.

Question 5

What are the reactions of carboxylic acid

Answer 5

• As an H⁺ donor (as an acid)
• to make esters

Question 6

what is the strength of a carboxylic acid

Answer 6

it is a weak acid

Question 7

what type of acid reactions do carboxylic acids undergo

Answer 7

• redox reactions with metals
• neutralisation reactions with bases ( alkalis, oxides, carbonates)

Question 8

what does acid reactions of carboxylic acids produce

Answer 8

carboxylic acids from carboxylate salts which are ionic compounds.
The complex anion is named after the carboxylic acid e.g. methanoic acid forms methanoate salts.

Question 9

what do redox reactions of carboxylic acids with salts produce

Answer 9

carboxylate salt + hydrogen

Question 10

what do neutralisation reactions with carboxylic acids and metal oxides produce

Answer 10

carboxylate salt + water

Question 11

what do neutralisation reactions with carboxylic acids and alkalis produce

Answer 11

carboxylate salt + water

Question 12

what do neutralisation reactions with carboxylic acids and carbonates produce

Answer 12

carboxylate salt + CO₂ + water

Question 13

How do carboxylic acids react to form esters

Answer 13

The reaction between carboxylic acid and an alcohol gives an ester. A catalytic amount of H⁺ from a strong acid (e.g. H₂SO₄) is required.
It is an equilibrium reaction so to produce more of the ester the water which is also produced in the reaction should be removed, to push equilibrium to the right.

Question 14

what is the functional group of esters

Answer 14

COOC

Question 15

Describe the solubility of esters

Answer 15

Esters contain a permenant dipole between C=O but a limited ability to form hydrogen bonds with water. They are held together by permenant dipole-dipole interactions.
Esters are therefore insoluble in water.

Question 16

describe how esters are named

Answer 16

The name comes from the alcohol and the acid which forms the ester.
The format is:
(carbon chain in the alcohol)yl (carbon chain in the acid)**oate)

Question 17

why is the reaction of a carboxylic acid and an alcohol not always favoured and what is the alternative(s)

Answer 17

The reaction of an acid and an alcohol is an equilibrium and therefore a 100% yeild cannot be obtained.
The reactions of acid anhydride or acyl chlorides with alcohols provide a better alternative.

Question 18

describe how an acid anhydride is formed

Answer 18

an acid anhydride is formed when two acids react and eliminate water

Question 19

describe the process of making ethyl propanoate

Answer 19

1. add 2cm³ of ethanol and 2cm³ of propanoic acid into a boiling tube
2. add drops of sulfuric acid
3. place boiling tube in an 80℃ water bath and leave for 5mins.
4. pour the boiling tube into a beaker containing NaOH to neutralise the acid

Question 20

define hydrolysis

Answer 20

hydrolysis is the chemical breakdown of a compoind in the presence of water or in aqueous solutions.

Question 21

define esterificaiton

Answer 21

esterification is the reaction of an alcohol with a carboxylic acid to form an ester

Question 22

What is the acid hydrolysis of an ester

Answer 22

acid hydrolysis of an ester is the opposite of esterification

Question 23

Describe what is carried out in acid hydrolysis esters

Answer 23

The ester is heated under reflux with dilute aqueous acid.
The ester is broken down by water, with the acid acting as a catalyst.
This is reversable

Question 24

Describe what is carried out in alkali hydrolysis of esters

Answer 24

Alkali hydrolysis is irreversible.
The acid is heated under reflux with NaOH (or aqueous hydroxide ions)
This produces a carboxylate salt and an alcohol

Question 25

How do you regain the carboxylic acid from a carboxylate salt

Answer 25

add a strong acid

Question 26

How do you from acyl chlorides

Answer 26

add SOCl₂ to their parent carboxylic acid.

The reaction shoudl be carried out in a fume cupboard as it priduces SO₂ and HCl as gases which are harmful

Question 27

what are the reactions of acyl chlorides

Answer 27

• with alcohols to form esters
• with phenols to form esters
• with water to form carboxylic acids
• with ammonia and amines to form amides.

Question 28

is a catalyst required for the reaction of acyl chlorides or acid anhydrides with phenols to form esters

Answer 28

No, they are more reactive than carboxylic acids

Question 28

why are acyl chlorides so useful

Answer 28

they are very reactive and can easily be converted into esters, carboxylic acids, amides with good yeilds.
They react with nucleophiles by losing the chloride ion whilst retaining the C=O.

Question 28

describe the reaction of ammonia and amines reacting with acyl chlorides

Answer 28

ammonia and amines can act as nucleophiles by donating the lone pair of electrons on th enitrogen to an electron deficient species.
The reaction with acyl chlorides forms amides.

Ammonia reacts with acyl chlorides to form a primary amide, here the nirtogen is attached to one carbon atom.

Question 29

what is the relative reactivity of acid anhydrides to acyl chlorides

Answer 29

acid anhydrides are less reactive than acyl chlorides but react in a similar way to acyl chlorides with alcohol, phenol, water, ammonia, and amines.