haloalkanes Flashcards
Name the type of mechanism used to turn haloalkanes into an alcohol (1)
nucleophillic substitution
State and explain how the rates of hydrolysis of the chloroalkane and the bromoalkane would differ (2)
- rate slower with chloroalkane
- C-Cl bond is stronger than C-Br bond
What measurment and observation would allow the student to compare the rates of hydrolysis (1)
time for precipitate to appear
1-iodopentane was found to react faster than 1-bromopentane Explain why. (2)
- C-I bond is weaker thane C-Br bond
- Carbon - halogen bond breaks
Alcohol are used in organic synthesis
pentan-2-ol can be prepared by the alkaline hydrolysis of 2 - iodopentane
the reaction mixture is boiled for 20 minutes
State the most appropriate technique that could be used to boil the reaction mixture for 20 minutes (1)
reflux
The rate of the hydolysis of a haloalkane depends on the halogen present State and explain how the halogen in the haloalkane affects the rate of hydrolysis (2)
- links rate of reaction to strength of bond /bond enthalpy eg the weaker the bond the fater the reaction stronger bond takes longer to break lower bond enthalpy reacts faster
- C-F bond is hydrolysed slowest
- C-I bond is hydrolysed faster than C-Br
the organic product in (i) can be formed faster uing a different haloalkane than 1 - bromobutane identify the haloalkane and explain your answer (1)
- 1-iodobutane
- C-I bonds are weaker
Give two sources of nitrogen oxides in the stratosphere (1)
- lightning
- aircraft
What does a curly arrow represent in mechanisms (1)
movement of an electron pair
What is meant by the term nucleophile (1)
electron pair donor
Radical substitution produces a mixture of organic products
Sugget two reason why (2)
- further substitution
- substitution at different positions along a chain
State two properties that make a good aerosol (1)
- low reactivity
- volaatile
- non toxic
Explain the following statements using equation where appropriate
* life on earth benefits from the precence of an ozone layer
* the concentration of ozone maintained in the ozone layer
* how CF2Cl2 produces radical which catalye the breakdown of the ozone (5)
- benefit of ozone layer to life - ozone absorbs UV radiation
- maintenane of O2 concentration - O3 reverible arrow O2 + O
- production of radicals from compound - CFCL2 -> Cl + CF2Cl
- breakdown of O3 - Cl +O3 ->CLO + O2
Give chemical explanations for the folowing statements
The rate of hydolysis of 1 - bromobutane is faster than that of 1 - chlorobutane (1)
The C-Br bond is weaker than the C-Cl bond
What is meant by the term structural isomers (1)
- having the same molecular formula but different structural formula
Suggest why an alkene is less soluble in water than either of alcohols (2)
- does not contain Oh groups
- does not form hydrogen bond with water
Suggest how CH3O- (methoxide ion) can act as a nucleophile (1)
- it is an electron pair donor
In this mechanism explain how CH3O- ions have acted a a nucleophile and suggest the type of bond fission that takes place (1)
- CH3O- donates an electron pair
- and heterolytic fission
Explain how CH3O- ions have acted a a base in the mechanism (1)
CH3O- accepted a proton
What do experimental reults tell you about the carbon - halogen bond enthalpies (1)
bond enthalpy decreases C-Cl>C-Br>C-I
Predict an approximate value for the bond angles in a molecule of CF3Cl (1)
- 108-111
Suggest a property than made CF3Cl uitable as a propellant in an aerosol (1)
- volatile / low boiling / gas / non toxic / non flammable / unreactive/ liquidies under pressure / inert
Explain what is meant by the tern homolytic fission (2)
- bond pair split equally
- bond breaking
Suggest which bond is most likely to be broken when CF3Cl is exposed to ultraviolet radiation Explain your answer (2)
- C-CL because it is the weaker bond
Identify the two free radicals most likely to be formed when CF3Cl is exposed to ultraviolet radiation (2)
- Cl
- CF3
Suggest two reasons why there is still concern about ozone depletion (2)
- CFCs take many years to reach the ozon layer or long residence time
- CFCs are still being used
- there are other ozone depleting substances
As part of an experiment he inhaled a lung full of dichlorodifluoromethane CCL2F2 and used it to blow out a candle
use the demenstration to suggest two properties of CCL2F2 explain with a reason two other uses of the chemicals such as CCl2F2 other than a refrigerant (4)
- non toxic
- non flammable
- aerosols - because it is volatile / unreactive/ non toxic
- degreasing agent - good solvent for organic material
- fire extinguishers - because it is non flammable
