Unit 2-Oxidation of Food

Question 1

Describe how to identify an alcohol (alkanol):

1. From the name
2. From a structure

Answer 1

1. Names end in -ol.
2. They contain the hydroxyl (OH) functional group.

Question 2

What steps are needed in order to name an alcohol (alkanol)?

Answer 2

1. Find the longest carbon chain and name it.
2. Number the carbon atoms in the chain so the hydroxyl group has the lowest possible number.
3. Identify any branches joined onto the main chain and name them.
4. Identify each branch by a number indicating its position. Use prefixes if needed.

Question 3

What is the systematic name of this alcohol (alkanol)?

Answer 3

3-methylpentan-2-ol

Question 4

What are the three types of alcohol molecules?

Answer 4

Primary, secondary and tertiary.

Question 5

What is different about primary, secondary and tertiary alcohol?

Answer 5

A primary alcohol is one in which the hydroxyl group (–OH) is attached to a carbon atom attached to one other carbon

A secondary alcohol is one in which the hydroxyl group (-OH) is attached to a carbon atom attached to two other carbons

A tertiary alcohol is one in which the hydroxyl group is attached to a carbon atom attached to three other carbons

Question 6

Are these alcohol primary, secondary or tertiary?

Answer 6

Secondary, tertiary and primary.

Question 7

Name these alcohols.

Answer 7

Propan-2-ol, 2-methylpropan-2-ol and propan-1-ol

Question 8

Compared with alkanes, alcohols have significantly higher boiling points.

Explain fully.

Answer 8

The hydroxyl groups in alcohol molecules are responsible for hydrogen bonding between the alcohol molecules.

As greater energy is required to overcome these strong intermolecular forces, the melting points and boiling points of alcohols are higher than those of alkanes with a corresponding chain length.

Question 9

Alcohols with a greater number of hydroxyl groups will have even higher boiling points.

What name is given to alcohols with:

two hydroxyl groups

three hydroxyl groups

Answer 9

Alcohols with two hydroxyl groups are called diols.

Alcohols with three hydroxyl groups are called triols.

Question 10

When carbon compounds are oxidised, what happens to the oxygen to hydrogen ratio?

Answer 10

When carbon compounds are oxidised, the oxygen to hydrogen ratio increases, so either oxygen atoms are being added to the compound, or hydrogen atoms removed.

Question 11

The oxidation of an alcohol can be brought about by using an oxidising agent.

Give an example of an oxidising agent which could be used.

Answer 11

Hot copper(II) oxide or acidified dichromate(VI) solutions

Question 12

Oxidation of primary alcohols forms two products in a two stage reaction.

Name them.

Answer 12

Primary alcohol → Aldehyde (Alkanals) → Carboxylic acid

Question 13

Secondary alcohols can only be oxidised once.
What is produced?

Answer 13

Secondary alcohol → Ketone (alkanone)

Question 14

Tertiary alcohols cannot be oxidised.

Why?

Answer 14

Tertiary alcohols have no hydrogen atoms on the carbon atom that holds the alcohol group. This means that they cannot undergo oxidation.

Question 15

Describe how to identify an carboxylic acid(alkanoic acid):

1. From the name
2. From a structure

Answer 15

1. Names end in -oic acid
2. They contain the carboxyl COOH functional group.

Question 16

What steps are needed in order name a carboxylic acid (alkanoic acid)?

Answer 16

1. Find the longest carbon chain and name it.
2. Identify any branches joined onto the main chain and name them.
3. Identify each branch by a number indicating its position. Use prefixes if needed.

Question 17

What is the systematic name of this carboxylic acid?

Answer 17

Propanoic acid