4) Alcohols and Haloalkanes

Question 1

What is the functional group of alcohols?

Answer 1

-OH.

Question 2

Why are alcohol molecules polar?

Answer 2

Alcohols have a polar O-H bond because of the difference in electronegativity of the oxygen and hydrogen atoms.

Question 3

If the carbon that the -OH group is attached to is attached to 1 other carbon itself, what is the classification of that alcohol?

Answer 3

Primary.

Question 4

If the carbon that the -OH group is attached to is attached to 2 other carbons itself, what is the classification of that alcohol?

Answer 4

Secondary.

Question 5

If the carbon that the -OH group is attached to is attached to 3 other carbons itself, what is the classification of that alcohol?

Answer 5

Tertiary.

Question 6

What do alcohols produce when they burn completely in a plentiful supply of oxygen?

Answer 6

Carbon dioxide and water.

Question 7

What is used to represent an oxidising agent?

Answer 7

[O].

Question 8

Primary and secondary alcohols can be oxidised using an oxidising agent. What is the usual mixture used?

Answer 8

• Potassium dichromate (VI) acidified with dilute sulfuric acid.
• K2Cr2O7/H2SO4.

Question 9

On oxidation, what does a primary alcohol form?

Answer 9

• Aldehyde.

- Carboxylic acid.

Question 10

How can you ensure an aldehyde is made when oxidising a primary alcohol?

Answer 10

Distil.

Question 11

How can you ensure a carboxylic acid is made when oxidising a primary alcohol?

Answer 11

Heat strongly under reflux.

Question 12

On oxidation, what does a secondary alcohol form?

Answer 12

Ketone.

Question 13

On oxidation, what does a tertiary alcohol form?

Answer 13

No reaction.

Question 14

How is an alkene made from an alcohol?

Answer 14

• An acid is heated under reflux in the presence of an acid catalyst, H2SO4 or H3PO4 to produce an alkene.
• Plus water as a by-product.

Question 15

What do alcohols form when they react with hydrogen halides?

Answer 15

Haloalkanes.

Question 16

How are haloalkanes formed from alcohols?

Answer 16

Substitution with halide ions in the presence of an acid (NaBr/H2SO4) to form haloalkanes.

Question 17

Explain why ethane-1,2-diol is very soluble in water.

Answer 17

• Has O–H bonds.

- Which forms hydrogen bonds with water.

Question 18

Butan-1-ol can be oxidised to form butanal. State a suitable oxidising mixture for this reaction.

Answer 18

• H+.

- Cr2O7^2-.

Question 19

State the colour change you would see during the oxidation of butan-1-ol to form butanal.

Answer 19

Orange to green.

Question 20

Explain what is meant by low volatility.

Answer 20

High boiling point/difficult to vapourise.

Question 21

Define intermolecular forces.

Answer 21

Bonds between molecules.

Question 22

What happens in the hydrolysis of a haloalkane?

Answer 22

The halogen atom is replaced by an -OH group. This is an example of nucleophilic substitution.

Question 23

Define what is meant by a nucleophile.

Answer 23

An electron pair donor.

Question 24

Use this card to test knowledge of the nucleophilic substitution mechanism.

Answer 24

Rate knowledge 1-5.

Question 25

Which haloalkanes react the quickest and slowest?

Answer 25

• 1-chlorobutane reacts the slowest and the C-Cl bond is the strongest.
• 1-iodobutane reacts the fastest and the C-Cl bond is the weakest.

Question 26

What is the trend in the rate of hydrolysis in terms of the carbon-halogen bond?

Answer 26

The rate of hydrolysis increases as the strength of the carbon-halogen bond decreases.

Question 27

Suggest three reasons why there is still concern about ozone depletion.

Answer 27

• CFCs take many years to reach the ozone layer.
• CFCs are still being used.
• There are other ozone depleting substances.

Question 28

State a suitable reagent for dehydrating an alcohol.

Answer 28

H2SO4 (heat).

Question 29

Suggest a property that made CF3Cl suitable as a propellant in an aerosol.

Answer 29

Volatile.

Question 30

Suggest which bond is most likely to be broken when CF3Cl is exposed to ultraviolet radiation. Explain your answer.

Answer 30

C-Cl because it is the weaker bond.

Question 31

The rates of hydrolysis of chloroethane, bromoethane and iodoethane are different. Explain why.

Answer 31

• I>Br>Cl.

- C-I bond weakest and C-Cl bond strongest.