Advices For Studying Organic Chemistry

Chain Initiation
Step 1 Cl–Cl 2 Cl• ∆H° = + 243 kJ mol–1
(∆H° = 243)

Chain Propagation
Step 2 CH 3 –H + •Cl CH 3 • + H–Cl ∆H° = + 4 kJ mol–1
(∆H° = 435) (∆H° = 431)

Step 3 CH 3 • + Cl–Cl CH 3 –Cl + •Cl ∆H° = – 106 kJ mol–1
(∆H° = 243) (∆H° = 349)

Chain Termination
CH 3 • + •Cl CH 3 –Cl ∆H° = – 349 kJ mol–1
(∆H° = 349)

CH 3 • + CH 3 • CH 3 –CH 3 ∆H° = – 368 kJ mol–1
(∆H° = 368)

•Cl + •Cl Cl–Cl ∆H° = – 243 kJ mol–1
(∆H° = 243)

2. In the chain-initiating step only the bond between two chlorine atoms is broken,
   and no bonds are formed.

1. The heat of reaction is simply the bond dissociation energy for a chlorine
   molecule, and it is highly endothermic.

3. In the chain-terminating steps bonds are formed, but no bonds are borken.
   
   
   1. All of the chain-terminating steps are highly exothermic.
   
   
   
   


4. In the chain-propagating steps, requires the breaking of one bond and the
   formation of another.
   
   
   1. The value of ∆H° for each of these steps is the difference between the bond
      dissociation energy of the bond that is broken and the bond dissociation energy
      for the bond that is formed.
   
   
   
   


5. The addition of chain-propagating steps yields the overall equation for the
   chlorination of methane:
   CH 3 –H + •Cl CH 3 • + H–Cl ∆H° = + 4 kJ mol–1