Chem 4311/6311
assignment-10-sykes-carbanions.docx
2016January17
1. Show all fundamental steps of the mechanism for one of the reactions at left and the major
products of the remaining two.
2. Show all fundamental steps of the mechanisms for the monochlorination of methylcyclopentane.
How many moles of initiator is required to monochlorinate methylcyclopentane?
3. Show all fundamental steps of the mechanisms for the following reactions.
4. Explain the relative rates of recombination of methyl and isopropyl radicals.
5. Explain the following trends.
R1
R2
R3
CH3
CH3
CH3
H
CH3
CH3
H
H
CH3
H
H
H
Relative
rate
13,000
111
11
1
1
Chem 4311/6311
assignment-10-sykes-carbanions.docx
2016January17
6. Show all fundamental steps of the mechanism for the following reactions for all products.
7. Show all fundamental steps of the mechanism for the following reaction.
8. Show all fundamental steps of the mechanism for the following reaction.
9. Calculate the relative amount of mono-halogenated isomers for each reaction indicated.
Bomination: CH =.
2(1600)
2(1600)+8(80)+6(1)
2(80)
= 0.832, C2 or C5 CH2 2(1600)+8(80)+6(1) = 0.0416
4(80)
6(1)
C4 and C6 CH2 2(1600)+8(80)+6(1) = 0.0832, CH3 = 2(1600)+8(80)+6(1) = 0.00156,
chlorination rate CH =
2(6.7)
2(6.7)+8(4.4)+6(1)
4(4.4)
= 0.245 , C2 or C5 CH2 =
2(4.4)
2(6.7)+8(4.4)+6(1)
= 0.161,
6(1)
C4 and C6 CH2 = 2(6.7)+8(4.4)+6(1) = 0.322 CH3 = 2(6.7)+8(4.4)+6(1) = 0.110 or 0.368 : 1 : 0.16532
10. Explain why the following reactions cannot be the propagation steps for methane radical
chlorination.
2
Chem 4311/6311
assignment-10-sykes-carbanions.docx
2016January17
3
11. Show all fundamental steps of the mechanism for the following reaction. Include formation of
benzene. Compared to 1,5-cyclooctadiene how much initiator is used? No carboxylic acid is formed.
12. Show all fundamental steps of the mechanisms for the following reactions.
13. (t-BuO)2 is often used as a radical initiator. Show the non-radical products it eventually forms if
there is nothing reactive present. Hint: review the possible fates (reactions) of radicals. Show all
fundamental steps of the mechanism for the second reaction.
.
Initiation: electron transfer, fragmentation to phenyl radical, oxidation by Cu 2+, phenyl cation addition
to benzoic acid or phenyl radical adds to peroxide
14. Isooctane is often used as a solvent for radical reactions, especially when oxygen radicals are
formed. Explain. Hint: consider the suitability of heptane versus isooctane.
Kinetics is the determining factors. If the reactions with isooctane are slower than with reagents
then the isooctane is kinetically inert even though the isooctane radicals may be relatively stable. Primary radicals lack
stabilization, the others are sterically hindered.
15. Show all fundamental steps of the mechanisms for the following reactions.
16. . Show all fundamental steps of the mechanism for the following reaction.
Chem 4311/6311
assignment-10-sykes-carbanions.docx
2016January17
4