Haloalkanes

Question 1

What are haloalkanes?

Answer 1

Organic compounds that contain carbon atoms and at least one halogen atom

Question 2

Are haloalkanes soluble in water?

Answer 2

Insoluble as C-H bonds are non polar and not compensated enough by C-X polarity

Question 3

What type of intermolecular forces do haloalkanes have?

Answer 3

London forces and permanent dipoles between C-X

Question 4

When would haloalkanes have higher boiling points?

Answer 4

Increased carbon chain length or a halogen further down group 7

Question 5

What is the most important factor in determining halogen reactivity?

Answer 5

The strength of carbon-halogen bond

Question 6

What would bond polarity suggest the order of reactivity would be?

Answer 6

C-F would be most reactive as its the most polar bond

Question 7

What would bond enthalpies suggest the order of reactivity would be?

Answer 7

C-I would be the most reactive as it has the lowest bond enthalpy

Question 8

Define nucleophile

Answer 8

Electron pair donor

Question 9

Give 3 examples of nucleophiles

Answer 9

:OH-
:CN-
:NH3

Question 10

What is nucleophilic substitution?

Answer 10

A reaction where a nucleophile donates a lone pair of electrons

Question 11

What is hydrolysis?

Answer 11

A reaction where water is a reactant that causes the breaking of a bond in a molecule (NaOH or KOH)

Question 12

What fission does water undergo to produce OH-

Answer 12

Heterolytic fision

Question 13

Why does the hydrolysis of 1-chlorobutane react the slowest?

Answer 13

Because the C-Cl- bond is the strongest

Question 14

What are CFCs?

Answer 14

Haloalkanes containing C, F and Cl only

Question 15

What is the problem with CFCs?

Answer 15

They catalyse the breakdown of ozone in the atmosphere via free radical substitution

Question 16

What is the main function of the ozone layer?

Answer 16

Provides protection from harmful UV radiation

Question 17

How does O3 form initially?

Answer 17

• Ozone has a delicate equilibrium
• Initially UV breaks O2 = O•
• O2 + O = O3
• Ozone rate of formation is the same as it breaks down

Question 18

Why are CFCs very stable?

Answer 18

Because of the strength of the carbon-halogen bonds within their molecules

Question 19

How do CFCs form radicals once it reaches the stratosphere?

Answer 19

UV radiation provides sufficient energy to break a carbon-halogen bond by homolytic fission, the Cl-Cl bond has the lowest enthalpy so is the bond that breaks

Question 20

Draw the mechanism to show the depletion of Cl• to the ozone layer

Answer 20

Cl2 = 2Cl•
Cl• + O3 = ClO• + O2
ClO• + O = Cl• + O2
2Cl• = 2Cl2