Haloalkanes

Question 1

Nucleophile definition

Answer 1

An electron pair donor

Question 2

What are 3 examples of nucleophiles?

Answer 2

OH, H2O, NH3

Question 3

What are NOT included in the equation of nucleophilic substitution?

Answer 3

Metal ions (aren’t reacting)

Question 4

How does rate of nucleophilic substitution change down the halogen group?

Answer 4

Down the group the C-X bond enthalpy gets smaller so bond strength decreases making it easier to break so the rate of reaction with nucleophiles increases

Question 5

What is the conversion, reagent and conditions of the hydrolysis of haloalkanes?

Answer 5

Conversion: haloalkane –> alcohol (+halide ion)
Reagent: water or aqueous metal hydroxide
Conditions: heat

Question 6

What is the setup for the hydrolysis of haloalkanes?

Answer 6

Test tubes in a water bath (provides H2O) with ethanol, AgNO3 (provides Ag+ which forms a ppt with halide ions) and a different haloalkane in each one

Question 7

What are the controlled variables for the hydrolysis of haloalkanes?

Answer 7

1. Constant temperature (water bath)
2. Same number of MOLES of each haloalkane
3. Same chain length/branching of each haloalkane

Question 8

What is measured during the hydrolysis of haloalkanes?

Answer 8

How long it takes for the precipitate to form

Question 9

What are the expected observations for the hydrolysis of haloalkanes?

Answer 9

• Cl form a white ppt (Ag+ + Cl- –> AgCl)
• Br forms a cream ppt
• I forms a yellow ppt

The AgI yellow ppt will form first because the C-I bond is weaker than the C-Cl or C-Br bonds so less energy is required to break it which increases rate of hydrolysis

Question 10

How does the ozone layer benefit life on earth?

Answer 10

Absorbs harmful UV radiation which can cause skin cancer

Question 11

What is the equation for formation and decomposition of ozone?

Answer 11

O2 + O ⇌ O3

Question 12

Why are chlorofluorocarbons (refrigerants) harmful?

Answer 12

When in the stratosphere they are broken down by UV light, forming Cl. radicals which catalyse the decomposition of ozone

Question 13

What is the initiation step for Cl. radicals breaking down ozone?

Answer 13

CF2Cl2 –> .CF2Cl + Cl.

C-Cl bond breaks because it’s weaker than C-F bond

Question 14

What are the 2 propagation steps of Cl. breaking down ozone?

Answer 14

1. Cl. + O3 –> ClO. + O2

2. ClO. + O –> Cl. + O2

Question 15

What is the overall equation for Cl. breaking down ozone?

Answer 15

O3 + O –> 2O2

Anything on both sides of the equation are cancelled out e.g. the catalyst and the intermediate

Question 16

What were CFCs replaced by?

Answer 16

C-H bond replaces one of the C-Cl bonds as it prevents the breakdown into Cl. radicals

Question 17

What are NO. radicals generated by?

Answer 17

1. Aeroplane engines
2. Lightning

(Require high energy to overcome Ea)

Question 18

What is the equation for NO. forming?

Answer 18

N2 + O2 –> 2NO.

Question 19

What are the 2 propagation steps of NO. breaking down ozone?

Answer 19

1. NO. + O3 –> NO2. + O2

2. NO2. + O –> NO. + O2

Question 20

What is the overall equation for NO. breaking down ozone?

Answer 20

O3 + O –> 2O2