4.2.2 Haloalkanes Flashcards
(17 cards)
What is the definition of a nucleophile?
A nucleophile is an electron pair donor.
What is the mechanism for hydrolysis of a primary haloalkane with aqueous alkali?
Nucleophilic substitution: the OH⁻ ion attacks the δ⁺ carbon
What reagent and conditions are used to hydrolyse a haloalkane using aqueous alkali?
Aqueous NaOH or KOH
What is formed when a haloalkane is hydrolysed with aqueous alkali?
An alcohol and a halide ion.
What reagents are used to hydrolyse haloalkanes using water?
Water with AgNO₃ and ethanol.
Why is ethanol used in the hydrolysis of haloalkanes with AgNO₃?
Ethanol acts as a mutual solvent
What is observed during hydrolysis of haloalkanes with AgNO₃ and ethanol?
A precipitate of silver halide forms.
How can you compare the rate of hydrolysis of different haloalkanes?
By measuring the time taken for a silver halide precipitate to form using AgNO₃ and ethanol.
What is the trend in rate of hydrolysis of primary haloalkanes?
C–I > C–Br > C–Cl due to decreasing C–X bond enthalpy.
Why does iodoalkane hydrolyse faster than chloroalkane?
The C–I bond has the lowest bond enthalpy and breaks more easily.
Write an equation showing the production of a chlorine radical from CF₂Cl₂ under UV light.
CF₂Cl₂ → CF₂Cl• + Cl•
Write the first propagation step in ozone breakdown by a chlorine radical.
Cl• + O₃ → ClO• + O₂
Write the second propagation step in ozone breakdown by a chlorine radical.
ClO• + O → Cl• + O₂
Why are chlorine radicals harmful in the atmosphere?
They catalyse the breakdown of ozone and are regenerated
What is one alternative radical that can catalyse ozone breakdown?
•NO (nitric oxide)
How has scientific understanding influenced policy on CFCs?
Scientific evidence of ozone depletion led to legislation banning or restricting CFC use.
What environmental concern is linked to organohalogen compounds?
They lead to ozone depletion due to formation of halogen radicals in the stratosphere.
