Chemistry Reference
In-Depth Information
Section 3.2
a
0
-
azobisisobutyronitrile. Illustrate how free radicals can recombine inside or outside the solvent cage
and be lost to the initiation process.
2. Illustrate one or more inorganic and also one or more organic peroxides.
3. How does solvent “cage” affect the initiating free radicals? Explain and illustrate.
4. Explain homolytic and heterolytic cleavage of peroxides.
5. Explain and give chemical equations for
1. What sources of initiating free radicals do you know? Illustrate the decomposition reaction of
a
,
redox
initiations with Fe++, Co++, and Ce++++ ions in
the reaction mixture.
6. How are peroxides such as benzoyl peroxide decomposed by aromatic tertiary amines. Show the
two postulated mechanisms for the reaction of benzoyl peroxide with dimethyl aniline.
Section 3.3
1. Describe the reaction of the initiating free radical with the monomer. Show this reaction with
equations, using a phenyl initiating radical and styrene monomer as an example.
2. Do the same as question 1, but with a redox mechanism, showing a sulfate ion-radical adding to
vinyl acetate.
Section 3.4
1. Illustrate the transition state in the propagation reaction.
2. Explain the steric. polar and resonance effects in the propagation reaction.
3. Explain why there is a tendency for a
trans
-
trans
placement in the propagation reactions when
carried out at low temperatures.
4. How does the reaction medium affect the propagation reaction?
5. What is ceiling temperature and what is the kinetic expression for this phenomenon?
6. Explain what is meant by autoacceleration and how does it manifest itself.
7. What is cyclopolymerization? Explain and give several examples.
Section 3.5
1. What are the three termination processes in free-radical polymerization?
2. What is meant by degenerative chain transferring? Illustrate back-biting. The telomerization
reaction.
3. What is meant by chain transferring constants?
4. Write the equation for the degree of polymerization including all the chain transferring constants.
In a benzoyl peroxide initiated polymerization of 2 moles of styrene in benzene at 85
C(
K
d
10
5
L/mol-s at 85
C). How much benzoyl peroxide will be required in the polymeri-
zation solution to attain an average molecular weight of 250,000? Assume that termination occurs
only by recombination and no chain-transferring takes place.
¼
8.94
