Carboxylic Acid Derivatives

Question 1

What is a derivative of a carboxylic acid?

Answer 1

A compound that can be hydrolysed to form the parent carboxylic acid.

Question 2

What group is present in carboxylic acids?

Answer 2

Acyl group.

Question 3

What does an acyl group look like?

Answer 3

An R group bonded to a carbonyl group (C=O) with a functional group attached to the C.

Question 4

What are 4 derivatives of carboxylic acids?

Answer 4

Ester, acyl chloride, acid anhydride, amide.

Question 5

How do you name an ester? Example?

Answer 5

Remove the -oic acid suffix from the parent carboxylic acid and replace it with -oate. The alkyl chain attached to the COO group is then added as the first name.
- E.g. methyl ethanoate.

Question 6

How do you name an acyl chloride? Example?

Answer 6

Remove the -oic acid suffix from the parent carboxylic acid and replace it with -oyl chloride.
- Propanoyl chloride.

Question 7

How is an acid anhydride formed? Example?

Answer 7

By the removal of water from two carboxylic acid molecules.
- Ethanoic anhydride + H2O.

Question 8

What 2 products are formed of an acid anydride and a carboxylic acid?

Answer 8

Acid anhydride + H2O.

Question 9

What is esterification?

Answer 9

The reaction of an alcohol with a carboxylic acid to form an ester.

Question 10

How is an alcohol prepared to an ester?

Answer 10

The alcohol is warmed with a carboxylic acid with a small amount of conc H2SO4, which acts as a catalyst.

Question 11

What is the equation of esterification?

Answer 11

Carboxylic acid + Alcohol = Ester + H20 (conc H2SO4 as a catalyst).

Question 12

What do esters smell like?

Answer 12

Sweet/fruity smells.

Question 13

How do you make an ester in a laboratory?

Answer 13

1. Pour an equal volume of alcohol and carboxylic acid into a boiling tube.
2. Add a few drops of c.H2SO4.
3. Place boiling tube in a beaker of hot water at 80C.
4. Leave boiling tube in water for 5 minutes.
5. Pour the contents of the boiling tube into a beaker with aqueous sodium carbonate.
6. The NaCO3 is a weak base so neutralises the carboxylic acid in the mixture so removes the smell so the smell of the ester is more distinctive.

Question 14

What 2 things can ester by hydrolysed by?

Answer 14

1. Acid.
2. Alkali.

Question 15

What is hydrolysis?

Answer 15

The chemical breakdown of a compound in the presence of water or in an aqueous solution.

Question 16

What is acid hydrolysis of an ester the opposite of?

Answer 16

Esterification.

Question 17

How do you carry out the acid hydrolysis of an ester?

Answer 17

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

Question 18

What is the equation for the acid hydrolysis of an ester?

Answer 18

Ester + Water = Carboxylic Acid + Alcohol.

Question 19

What is alkaline hydrolysis?

Answer 19

Also known as saponification and is irreversible. The ester is heated under reflux with aqueous OH- ions.

Question 20

What is the equation for the alkaline hydrolysis of an ester?

Answer 20

Ester + OH- = Carboxylate ion + Alcohol.

Question 21

What is an example of an esterification reaction?

Answer 21

Propanoic acid + Ethanol = Ethyl propanoate + Water.

Question 22

What is an example of an acid hydrolysis reaction of an ester?

Answer 22

Methyl 2-hydroxybenzoate + Water = 2-hydroxybenzoic acid + Methanol.

Question 23

What is an example of an alkaline hydrolysis reaction of an ester?

Answer 23

Methyl ethanoate + OH- (aq) = Ethanoate ion + Methanol.

Question 24

What is the hydroxide ion is a compound in alkaline hydrolysis of an ester? Example?

Answer 24

Metal ester is formed.
- E.g. Sodium ethanoate: CH3COO-Na+.

Question 25

How are acyl chlorides prepared?

Answer 25

Directly from their parent carboxylic acid by reaction with thionyl chloride, SOCl2. SO2 and HCl are evolved as gases, leaving just the acyl chloride.

Question 26

Where should acyl chloride reactions be carried out? Why?

Answer 26

In a fume cupboard as the products are harmful.

Question 27

What is an example of a reaction of an acyl chloride being prepared?

Answer 27

Propanoic acid + SOCl2 = Propanoyl chloride + SO2 (g) + HCl (g).

Question 28

What is the equation of the reaction of an acyl chloride being prepared?

Answer 28

Carboxylic acid + SOCl2 = Acyl chloride + SO2 (g) + HCl (g).

Question 29

Why are acyl chloride very useful in chemistry (2)?

Answer 29

1. They are very reactive. 2. Useful in organic synthesis as they can be easily converted into carboxylic acid derivatives, such as esters and amides, with good yields.

Question 30

What do acyl chlorides react with? Form?

Answer 30

With nucleophiles by losing the chloride ion whilst retaining the C=O double bond.

Question 31

What 2 things to acyl chlorides react with to form esters?

Answer 31

1. Alcohols. 2. Phenols.

Question 32

What do acyl chlorides react with to form carboxylic acids?

Answer 32

Water.

Question 33

What do acyl chlorides react with to form amides?

Answer 33

Ammonia and amines.

Question 34

What is the equation of acyl chlorides with alcohols to form esters?

Answer 34

Acyl chloride + Alcohols = Esters + HCl.

Question 35

What is an example of an equation of acyl chlorides with alcohols to form esters?

Answer 35

Ethanoyl chloride + Propan-1-ol = Propyl ethanoate + HCl.

Question 36

What is the equation of acyl chlorides with phenols to form esters?

Answer 36

Acyl chloride + Phenol = Phenyl ester + HCl.

Question 37

Why are acyl chlorides used to form esters with phenols?

Answer 37

Because carboxylic acids are not reactive enough to form esters with phenols. Acyl chlorides and acid anhydrides are both more reactive than carboxylic acids and react with phenols to produce phenyl esters. Neither reactions needs a catalyst.

Question 38

What is an example of an equation of acyl chlorides with phenols to form esters?

Answer 38

Ethanoyl chloride + Phenol = Phenyl ethanoate + HCl.

Question 39

What is the equation of acyl chlorides with water to form carboxylic acids? Type of reaction?

Answer 39

Acyl chloride + Water = Carboxylic acid + HCl. - Reacts vigorously.

Question 40

What is an example of an equation of acyl chlorides with water to form carboxylic acids?

Answer 40

Ethanoyl chloride + Water = Ethanoic acid + HCl.

Question 41

What is observed when ethanoyl chloride reacts with water?

Answer 41

Steamy fumes of HCl are observed.

Question 42

How does ammonia and amines react with acyl chlorides?

Answer 42

Ammonia and amines can act as nucleophiles by donating the lone pair of electrons on the nitrogen atom to an electron-deficient species.

Question 43

What is formed when ammonia reacts with acyl chlorides?

Answer 43

A primary amide.

Question 44

How can you identify a primary amide?

Answer 44

In the primary amide the nitrogen atom is attached to one carbon.

Question 45

What is the equation when ammonia reacts with acyl chlorides to form primary amides?

Answer 45

Acyl chloride + Ammonia = Primary amide + Ammonium chloride.

Question 46

What is an example of a reaction when ammonia reacts with acyl chlorides to form primary amides?

Answer 46

Ethanoyl chloride + 2NH3 = Ethanamide + NH4Cl.

Question 47

What is formed when primary amines react with acyl chlorides?

Answer 47

A secondary amide.

Question 48

How can you identify a secondary amide?

Answer 48

In the secondary amide the nitrogen atom is attached to two carbon.

Question 49

What is the equation when a primary amine reacts with acyl chlorides to form secondary amides?

Answer 49

Acyl chloride + Primary amine = Secondary amide + Ammonium chloride.

Question 50

What is an example of a reaction when a primary amine reacts with acyl chlorides to form secondary amides?

Answer 50

Ethanoyl chloride + Methylamine = N-methanamide + methylammonium ion.

Question 51

What is the equation for an acid anhydride and phenol?

Answer 51

Acid anhydride + Phenol = Phenyl ester + Carboxylic Acid.

Question 52

What is an example of a reaction for an acid anhydride and a phenol?

Answer 52

Ethanoic anhydride + Phenol = Phenyl ethanoate + Ethanoic acid.

Question 53

What is the difference in reactivity between acid anhydrides and acyl chlorides? Useful?

Answer 53

Acid anhydrides are less reactive than acyl chlorides and are useful in laboratory experiments where acyl chlorides may be too reactive.

Question 54

What is the mechanism of nucleophilic addition - elimination? (2)?

Answer 54

1. Addition: lone pair of electrons from nucleophile is attracted and donated to the positive carbon in the C=O group of the acyl chloride. A dative covalent bond is formed between the nucleophile and the carbonyl carbon atom. The Pi bond of the C=O group breaks, forming a negatively charged intermediate. 2. Elimination: lone pair of electrons on the oxygen reforms the C=O double bond, causing a chloride ion to be removed. A proton is also then lost to complete the elimination.