Chapter 15

Question 1

What is a haloalkane?

Answer 1

Haloalkanes are compounds containing carbon, hydrogen and at least one halogen

Question 2

Are haloalkanes polar?

Answer 2

Haloalkanes are polar because of the carbon halogen bond, as the halogen are more electronegative. This means the carbon can be attacked by a nucleoohile.

Question 3

What is a nucleophile?

Answer 3

An electron pair donor such as OH- CN- or NH3

Question 4

What type of mechanism is the hydrolysis of a haloalkane?

Answer 4

Nucleophilic substitution

Question 5

Explain the process of hydrolysis of a haloalkane by aqueous alkali

Answer 5

1) the nucleophile attacks the partially positive carbon atom and donates it’s lone pair
2) a bond forms between the nucleophile and the carbon
3) the carbon-halogen bond breaks by heterolytic fission and an organic product and a halide ion is formed

Question 6

Draw the nucleophilic substitution of C2H5Cl with either OH-, CN- or NH3

Answer 6

Check with notes

Question 7

How can you test the rate if hydrolysis on different carbon-halogen bonds ?

Answer 7

Nucleophilic substitution by water in the presence of AgNO3

1) add 1cm3 of ethanol to three test tubes and two drops of chloro/bromo/iodo butane
2) add them to a water bath at 60 degrees
3) add a test tube of silver nitrate to the water bath
4) add 1cm3 of silver nitrate to each and time how long it takes for a precipitate to form

Question 8

Which haloalkanes are most reactive and why?

Answer 8

Reactivity increasess down the group because the bond strength decreases down the group with C-F having the highest bond enthalpy . This is because fluorine is much smaller so the binding electrons are more attracted to its positive nucleus

Question 9

What is the ozone layer and why is it important?

Answer 9

The ozone layer is part of the atmosphere partially made up of O3 which absorbs biologically damaging UV-B radiation

Question 10

What are CFCS

Answer 10

CFC are very useful, stable, very inert compound used as refrigerants, in air con units and aerosols

Question 11

Describe why and how CFC’s were banned and replaced

Answer 11

Satellite images showed the ozone layer above Antarctica was depleting and in 1973 two chemists put forward the mechanism for chlorine catalysed ozone destruction and presented evidence that the low reactivity increases their life span

Question 12

Write out the free radical substitution of CF2CL2

Answer 12

Check in textbook

Question 13

Write out the free radical substitution of one other natural radical that breaks down ozone

Answer 13

Nitrogen oxide is formed naturally in lightning strikes