1. O2 CHAIN INITIATION Name for this step: Cl2 + h  2Cl*
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane
Name for this step: Cl2 + h  2Cl*
CHAIN INITIATION
What common molecule can stop or slow the free radical substitution reaction ? O2

2. What is the second step of the methane chlorination mechanism ?
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
What is the second step of the methane chlorination mechanism ?
Step 2) Cl* + CH4  HCl + CH3* (radical)
What is the name of the step(s) that rationalize the high photoyield of the methane chlorination reaction ?
CHAIN PROPAGATION

3. CH3* + Cl2  CH3Cl + Cl* TERMINATES THE CHAIN REACTION
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
Radical-radical recombination reactions have what effect on the radical chlorination reaction of methane ?
TERMINATES THE CHAIN REACTION
What step follows:
Step 2)
Cl* + CH4  CH3* + HCl
STEP 3)
CH3* + Cl2  CH3Cl + Cl*

4. Which of the 5 facts is missing ??
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
Which of the 5 facts is missing ??
reaction will only go at >250oC in dark or with input of ultraviolet (uv) light.
in xs Cl2 , a single photon (h) event causes thousands of halogenations.
O2 causes halogenation reaction to slow or stop.
Reactivity rate follows: F2 > Cl2 > Br2 >I2
Wavelength of uv light that initiates reaction is the decomposition wavelength for the halogen

5. Which is not a step in the radical chlorination mechanism of methane?:
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
Which is not a step in the radical chlorination mechanism of methane?:
Cl* +CH4  CH3* + HCl
Cl* +Cl*  Cl2
CH3 + HCl  CH3Cl + H*
Cl2 + CH3* CH3Cl + Cl*
c) CH3 + HCl  CH3Cl + H*

6. Chain termination, chain initiation and chain _______________
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
Chain termination, chain initiation and chain _______________
propagation
What reaction explains the quenching effect of O2 on the radical substitution of Cl on methane ??
CH3* + O2 CH3OO *
methylperoxy radical (~ stable)

7. Activation barrier/energy
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
Activation barrier/energy
energy
Step 2:
CH4 + Cl*
What’s this barrier/energy
called ?
What reaction step and reaction here ?
Time or reaction progress

8. HX + CH3* What does the Xmas seal `activated complex’ sign stand for ?
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
What does the Xmas seal
sign stand for ?
`activated complex’
energy
HX + CH3*
What species lives here?
Time or reaction progress

9. Step 3: Cl2 +CH3 CH3Cl + Cl* What reaction step and reaction here ?
Drill and Practice with Free Radical Substitution Mechanism for Chlorination of Methane (continued)
What reaction step and reaction here ?
energy
Step 3:
Cl2 +CH3 CH3Cl + Cl*
Name of postulate connected to activated complex picture
Hammond Postulate
Time or reaction progress

10. ANY DAY DOING
ORGANIC CHEMISTRY
IS A ____________DAY
GOOD