AQA A Level Chemistry-Halogenoalkanes Revision Questions and Answers

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 free radicals What are the 3 steps of the chlorination of methane? Initiation, propagation, termination