Chapter 26 - Carbonyls and carboxylic acids

Question 1

describe the oxidation of aldehydes

Answer 1

they can be oxidised to carboxylic acids when reflux with acidified dichromate ions

Question 2

do ketones undergo oxidation reactions?

Answer 2

no

Question 3

what type of reaction is common in carbonyls?

Answer 3

nucleophilic addition

Question 4

aldehydes can be reduced to form what?

Answer 4

Primary alcohols

Question 5

what is used to detect carbonyls and what will be the positive result?

Answer 5

Brady’s Regent and a yellow/orange precipitable forms

Question 6

what is used to distinguish between aldehydes and ketones?

Answer 6

tollen’s reagent

Question 7

how do you make tollen’s reagent?

Answer 7

add aqueous sodium hydroxide to 3 cm of aqueous silver nitrate until a brown precipitate of silver oxide is formed, then add dilute ammonia until the brown precipitate dissolves

Question 8

what is the positive test for aldehydes?

Answer 8

A silver mirror will form

Question 9

what two groups does the carboxyl group contain?

Answer 9

A carbonyl group and a hydroxyl group

Question 10

why are carboxylic acids soluble?

Answer 10

The C-O and O-H bonds are polar allowing them to form hydrogen bonds with the water

Question 11

What is the maximum number of carbons a carboxylic acid can have before it becomes insoluble?

Answer 11

four

Question 12

are carboxylic acids strong or weak

Answer 12

Weak

Question 13

what are the two main reactions that carboxylic acids undergo?

Answer 13

redox and neutralisation

Question 14

what are the products when an aqueous solution of carboxylic acid reacts with a metal?

Answer 14

Hydrogen gas and the carboxylate salt

Question 15

what are the products when a carboxylic acid reacts with a metal oxide?

Answer 15

a Salt and water

Question 16

what are the products when a carboxylic acid reacts with an alkali?

Answer 16

a Salt and water

Question 17

What are the products when a carbonate reacts with a carboxylic acid?

Answer 17

a salt, water and carbon dioxide

Question 18

What is a derivative of a carboxylic acid?

Answer 18

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

Question 19

give four examples of derivatives of carboxylic acids

Answer 19

Estes, acyl chlorides, acid anhydrides and amides

Question 20

how is an ester named?

Answer 20

Remove the oic acid suffix from the parent carboxylic acid and replace with oate. The chain attached the oxygen atom of the COO group is an added at the start.

Question 21

how is an acyl chloride named?

Answer 21

remove oic and replace it with oyl chloride

Question 22

how is an acid anhydride formed?

Answer 22

By the removal of water from two carboxylic acid molecules

Question 23

what is esterification?

Answer 23

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

Question 24

what conditions are needed for esterification?

Answer 24

warm with a small amount of concentrated sulphuric acid which acts as a catalyst

Question 25

what two chemicals can esters be hydrolysed by?

Answer 25

Aqueous acid or alkali

Question 26

What is acid hydrolysis of an ester the reverse of?

Answer 26

Esterification

Question 27

describe the acid hydrolysis of an ester

Answer 27

The Ester is heated under reflux with dilute aqueous acid. Ester is then broken down by water with the acid acting as a catalyst.

Question 28

which one out of acid hydrolysis and alkali hydrolysis is reversible?

Answer 28

Acid hydrolysis

Question 29

how can acyl chlorides be prepared and what are the other products of this reaction?

Answer 29

they can be prepared directly from their parent carboxylic acid by reaction with thionyl chloride, the other products of this reaction SO2 and HCL are evolved as gases.

Question 30

why are acyl chlorides useful?

Answer 30

they are very reactive and in organic synthesis can be easily converted into carboxylic acid derivatives with good yields

Question 31

what kind of compound do acyl chlorides react with?

Answer 31

nucleophiles

Question 32

acyl chlorides react with alcohols to form what?

Answer 32

esters

Question 33

why can’t carboxylic acids react with phenols to form esters?

Answer 33

They are not reactive enough

Question 34

acyl chlorides and acid anhydrides can react with phenols to form what?

Answer 34

phenyl esters

Question 35

What happens when water reacts with acyl chlorides?

Answer 35

A violent reaction takes place with the evolution of dense steamy hydrochloric acid fumes. A carboxylic acid is also formed.

Question 36

Acyl chlorine react with ammonia form what?

Answer 36

A primary amide

Question 37

A primary amine reacts with an acyl chloride to form what?

Answer 37

a secondary amide

Question 38

Why are acid anhydrides useful?

Answer 38

they react in a similar way to acyl chlorides but are less reactive