Aldehydes and Ketones

Question 1

Oxidising agents will react with all the aldehydes to produce what?

Answer 1

Carboxylic acids

Question 2

What happens when Tollens’ Reagent is heated with an Aldehyde?

Answer 2

When heated with an Aldehyde, the Ag+ ions in Tollens’ reagent are reduced to Ag atoms and a silver mirror forms after a few minutes

Question 3

What happens when Fehling’s Solution is heated with an Aldehyde?

Answer 3

When it is heated with an Aldehyde, the copper (II) ions are reduced to a brick-red precipitate of Copper (I) oxide

Question 5

What is Tollens’ Reagent?

Answer 5

It is a colourless solution of silver nitrate dissolved in aqueous ammonia

Question 6

What happens when a ketone is heated with Fehling’s Solution?

Answer 6

There is no reaction so no precipitate is formed

Question 7

When Primary Alcohols are oxidised, what are the products?

Answer 7

Aldehydes and Carboxylic acids

Question 8

What is the reducing agent used to turn Aldehydes/Ketones back into alcohols?

Answer 8

NaBH4 (Sodium tetrahydridoborate (III)) dissolved in water with methanol

Question 10

In an equation, how is a reducing agent written?

Answer 10

[H]

Question 11

What is the mechanism for turning an Aldehyde/Ketone back into an Alcohol?

Answer 11

Nucleophilic Addition

Question 12

What acts as the nucleophile in this reaction and where does it come from?

Answer 12

The H- ion acts as the nucleophile and comes from the reducing agent

Question 14

For the Aldehyde/Ketone to be turned back into an Alcohol, where do the H+ ions come from?

Answer 14

Usually from water or from the Addition of a weak Acid

Question 16

What’s produced when potassium cyanide reacts with carbonyl compounds?

Answer 16

Hydroxynitriles (molecules with a CN and an OH group)

Question 17

Give an equation to show the dissociation of KCN in water

Answer 17

KCN –> K+ + CN-

Question 18

What are some risks associated with Potassium Cyanide?

Answer 18

It is an irritant and is extremely dangerous if ingested or inhaled

Question 19

What is the position of the carbonyl group in an Aldehyde?

Answer 19

Aldehydes have their carbonyl group at the end of the carbon chain

Question 20

To reduce risks, what should people do when working with KCN?

Answer 20

Wear gloves, safety goggles and a lab coat and perform the experiment in a fume cupboard

Question 21

If you start with an unsymmetrical ketone or an Aldehyde (except methanol) what will be produced when a hydroxynitrile is formed?

Answer 21

A mixture of enantiomers

Question 22

What is Fehling’s Solution?

Answer 22

It is a blue solution of Copper (II) Ions dissolved in NaOH

Question 23

When KCN reacts with moisture, what does it produce?

Answer 23

Hydrogen Cyanide which is a highly toxic gas

Question 24

What is produced when secondary alcohols are oxidised?

Answer 24

Ketones

Question 26

What is the mechanism when potassium cyanide reactions with a carbonyl compound?

Answer 26

Nucleophilic Addition

Question 32

What happens when Tollens’ Reagent reacts with a Ketone?

Answer 32

Ketones can’t be oxidised by Tollens’ Reagent so there’s no reaction or colour change