4.5 - Haloalkanes

Question 1

Define nucleophile

Answer 1

electron pair donor

Question 2

Haloalkane to alcohol

Answer 2

NaOH (aq)
nucleophilic substitution

Question 3

Draw nucleophilic substitution mechanism for haloalkane -> alcohol (hydrolysis)

Question 4

How does strength of carbon-halogen bond affect rate of hydrolysis?

Answer 4

weaker carbon-halogen bond = faster rate of hydrolysis
strongest to weakest: C-F, C-Cl, C-Br, C-I

Question 5

How to measure hydrolysis rate in primary haloalkanes experimentally?

Answer 5

• 1cm3 ethanol and few drops of 1-chloro/bromo/iodobutane in 3 test tubes
• (to increase rate/complete experiment in less time) add this and test tube with silver nitrate in to water bath at 60°C. allow to reach constant temp
• add 1cm3 silver nitrate to each test tube quickly and start stopwatch
• observe time for precipitate to form (white = Cl- /cream = Br- /yellow = I-)

Question 6

What measurement should you take to compare the rates of hydrolysis?

Answer 6

time for precipitate to appear

Question 7

Equation for breakdown of ozone (how ozone layer is maintained)

Answer 7

O2 + O ⇌ O3

Question 8

Equation for breakdown of CFCs to radicals

Answer 8

CF2Cl2 -> CfCl* + Cl*
requires UV

Question 9

Mechanism for breakdown of ozone

Answer 9

Propagation: Cl* + O3 -> ClO* + O2
ClO* + O -> Cl* +O2
Overall: O3 + O -> 2O2

Question 10

Mechanism for formation of NO

Answer 10

NO* + O3 -> NO2* + O2
NO2* + O -> NO* + O2
Overall: O3 + O -> O2

Question 11

Describe how life on Earth benefits from an ozone layer

Answer 11

• ozone absorbs UV
• UV at Earth’s surface is reduced

Question 12

State 2 sources of nitrogen oxides in the atmosphere

Answer 12

thunderstorms
aircraft