AQA CHEMISTRY

• What is heterolytic fission?

  Where one ion gets both electrons from the covalent bond
• What are produced by heterolytic fission?

  Ions
• What is a free radical?

  An atom or group with an unpaired electron, which is highly reactive as it wishes to pair up this electron
• What are 3 examples of situations where a free radical can be formed?

  During thermal cracking, during the reaction of halogens and methane, by homolytic fission
• What is homolytic fission?

  A reaction where each atom gets one electron from the covalent bond
• What are formed by homolytic fission?

  Free radicals
• What are the reagents in the chlorination of methane?

  Chlorine and methane
• What are the conditions needed for the chlorination of methane?

  UV Light or possibly heat
• What sort of reaction is the chlorination of methane?

  Free radical substitution
• Why is the chlorination of methane a chain reaction?

  Because during the propagation step, one radical is produced for each one used
• Why do Cl2 molecules produce chlorine free radicals when exposed to UV light?

  Because of their low bond enthalpy
• What reaction occurs during the initiation step of the chlorination of methane?

  Cl2 ----> 2Cl•
• What are the 3 steps of the chlorination of methane?

  Initiation, propagation, termination
• What 2 reactions occur during the propagation step of the chlorination of methane?

  1. Cl• + CH4 ----> CH3• + HCl

  2. Cl2 + CH3• ----> CH3Cl + Cl•
• What 3 reactions occur during the termination step of the chlorination of methane?

  1. CH3• + CH3• ----> C2H6

  2. CH3• + Cl• ----> CH3Cl

  3. Cl• + Cl• ----> Cl2
• What happens to CFCs under UV light?

  They decompose and a Cl radical is formed
• What are the two reactions in the Cl radical-catalysed conversion of O3 into O2?

  1. Cl• + O3 ----> ClO• + O2

  2. ClO• + O3 ----> 2O2 + Cl•
• What is the overall reaction for the conversion of ozone into oxygen?

  2O3 ----> 3O2
• What is an electrophile?

  A positive ion or atom with areas of slightly positive charge, which attacks electron-rich areas such as C=C double bonds
• What is a nucleophile?

  An atom with a lone pair of electrons, which attack electron-deficient areas (those with a positive or slightly positive charge) on atoms
• Do nucleophiles have to have a negative charge?

  Not necessarily, just a lone pair of electrons
• What is the reagent of the nucleophilic substitution of a hydroxide into a haloalkane?

  Sodium or Potassium Hydroxide aqueous solution
• What are the conditions of the nucleophilic substitution of a hydroxide into a haloalkane?

  Reflux in an aqueous solution
• What is the product of the nucleophilic substitution of a hydroxide into a haloalkane?

  An alcohol
• What is the reagent of the nucleophilic substitution of a cyanide into a haloalkane?

  Aqueous, alcoholic potassium/sodium cyanide
• What are the conditions of the nucleophilic substitution of a cyanide into a haloalkane?

  Reflux in an aqueous, alcoholic solution
• What is the product of the nucleophilic substitution of a cyanide into a haloalkane?

  A nitrile
• What is the reagent of the nucleophilic substitution of an ammonia into a haloalkane?

  Aqueous, alcoholic ammonia (in excess)
• What are the conditions of the nucleophilic substitution of an ammonia into a haloalkane?

  Reflux in aqueous, alcoholic solution under pressure
• What is the product of the nucleophilic substitution of an ammonia into a haloalkane?

  A primary amine
• What can happen if nucleophilic substitution of ammonia occurs without excess ammonia?

  Further substitution, creating secondary or tertiary amines or a quaternary ammonium salt
• What is the difference between primary, secondary and tertiary amines?

  Primary has 1 carbon chain coming off, secondary 2, tertiary 3
• What is a base?

  A proton acceptor
• What is the reagant in the nucleophilic elimination of an OH ion with a haloalkane?

  Alcoholic sodium/potassium hydroxide
• What is the product of the nucleophilic elimination of an OH ion with a haloalkane?

  An alkene
• What are the conditions of the nucleophilic elimination of an OH ion with a haloalkane?

  Reflux in alcoholic solution
• What does rate of reaction depend upon in nucleophilic substitution?

  Strength of the carbon-halogen bond
• Why does the strength of the carbon-halogen bond decrease as you go down the group?

  Because the atomic radius of the halogen increases as you go down the group, so the area of the covalent bond also increases, making it easier for electrons to be removed
• Which two reagants can turn a haloalkane into an alcohol?

  Sodium/potassium hydroxide and water
• What is a cis isomer?

  A (z) isomer