Chapter 23

Question 1

Addition Reaction

Answer 1

• Polarisation - C=C double bond un ethene becomes polarised because of repulsion by the electrons
• Heterolytic fission - induced polarisation becomes so great that Br2 molecule splits and two different species are formed
• Carbonium Ion formation - Br+ attached C2H4 to be stable and forms a covalent bond with a canon atom
• Ionic addition - Other carbonium ion is attacked by Br ion

Question 2

Evidence for addition reaction

Answer 2

When ethene reacts with bromine water that contains NaCl

1,2-dibromoethane and 1-bromo-2-chlorothane and another compound is formed

Question 3

Substitution Reaction

Answer 3

• Initiation - A chlorine is broken down to 2 Cl free radicals in UV light (homolytic fission)
• Propagation - A Cl radical attacks a methane molecule to form hydrogen chloride and a methyl free radical
• Propagation - A methyl free radical attacks a chlorine atom to form chloromethane and a chlorine free radical
• Termination - Cl + Cl -> Cl2 , Cl + CH3 -> CH3Cl , CH3 + CH3 -> C2H6

Question 4

A free radical

Answer 4

An atom or groups of atoms with unpaired electrons