haloalkanes [O1] PAPER 2 Flashcards
[X=halogen]
reaction between a haloalkane and NaOH to form an alcohol and NaX
- conditions?
- mechanism?
- what is the role of NaOH?
- warm, aqueous
- nucleophilic substitution
- nucleophile
[X=halogen]
reaction between a haloalkane and KCN to form a cyanide and KX
- conditions?
- mechanism?
- what is the role of CN?
- warm, ethanolic, aqueous
- nucleophilic substitution
- nucleophile
[X=halogen]
reaction between a haloalkane and ammonia to form an amine
- conditions?
- mechanism?
- what is the role of NH3?
- excess concentrated ethanolic NH3
- nucleophilic substitution
- nucleophile
[X=halogen]
reaction between a haloalkane and KOH to form an alkene, water and KX
- conditions?
- mechanism?
- role of OH ions?
- hot, ethanolic
- elimination
- base
what is a nucleophile?
electron pair donor
what are the three steps of free-radical substitution?
- initiation
(molecule -> radical + radical) - propagation
(molecule + radical -> radical + molecule) - termination
(radical + radical -> molecule)
what conditions are required for free-radical substitution and why?
• UV light
• break (C-X, C-H) bonds
[X=halogen]
what is (1) the overall equation for the formation of chloromethane from methane and (2) the mechanism?
(1) CH4 + Cl2 -> CH3Cl + HCl
[for balancing - number of substitutions = number in front of HCl and Cl2]
(2) free-radical substitution
write an equation to represent the overall decomposition of ozone into oxygen
2O3 -> 3O2
what is the species responsible for the catalytic decomposition of ozone in the upper atmosphere?
Cl• (chlorine free-radical)
write two equations that show how chlorine atoms (Cl•) act as a catalyst in the decomposition of ozone and explain how these reactions show that Cl• is a catalyst
Cl• is unchanged at the end
during an experiment carried out within a lab, why are small amounts of the reactants used for the experiment, considering sulfur dioxide is one of the products
sulfur dioxide is toxic
why would a molecule with C–Br bonds react faster than a molecule with C–Cl bonds in the same conditions?
C–Br is weaker than C–Cl
(as Cl is more electronegative)
Explain why a single chlorine radical can cause the decomposition of many molecules of ozone.
Cl• is regenerated and causes a chain reaction in the decomposition of ozone
Give one reason why bonds in molecules such as carbon dioxide and 1,1,1-trifluoroethane absorb infrared radiation.
because the bonds vibrate
OR
because the bonds are polar
Explain why the halogenoalkane is attacked by the nucleophile in a nucleophilic substitution reaction.
[X = halogen]
• X is more electronegative than carbon
• Carbon is partially positive
• Lone electron pair on the nucleophile is donated to the partially positive carbon
State why the ozone layer is beneficial for living organisms.
absorbs harmful uv
State how chlorofluorocarbons (CFCs) form chlorine atoms in the upper atmosphere.
C–Cl bonds break
