Deck 10: Free-Radical Reactions, Main-Group Organometallic Compounds, and Carbenes

Question 1

Complete the reaction by giving the missing product.

Answer 1

Question 2

Give the structure of the organic free-radical intermediate formed in the propagation steps in the reaction of the alkene with HBr in the presence of peroxides.

Answer 2

The bromine will add to the less substituted alkene carbon and generate the more stable radical, the tertiary radical. The structure of the free-radical intermediate is

Question 3

Give the product A that results when HBr undergoes peroxide-mediated addition to 1-methylcyclopentene. Also give the structure of the free-radical intermediate B (other than Br.) in the propagation steps of this reaction.

Answer 3

Question 4

Treatment of (+)-(R)-3-methyl-1-pentene with HBr and peroxides yields (-)-1-bromo-3-methyl pentane. Determine the stereochemical configuration of the product.

Question 5

Thiols (R-S-H) undergo addition to alkenes but only in the presence of peroxides. This equation is an example.
$$\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm { C } = \mathrm { CH } _ { 2 } + \mathrm { RSH } \stackrel { \text { peroxides } } { \longrightarrow } \left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm { CH } - \mathrm { CH } _ { 2 } \mathrm { SR }$$ Which one of these is a reactive intermediate in this reaction?
(a) $\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm { C } - \dot { \mathrm { C } } \mathrm { H } _ { 2 } - \mathrm { SR }$
(b)

(c) $\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \stackrel { + } { \mathrm { C } } - \mathrm { CH } _ { 2 } - \mathrm { SR }$

(d) $\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \dot { \mathrm { C } } - \mathrm { CH } _ { 2 } - \mathrm { SR }$

(e)


(f) $\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \dot { \mathrm { C } } - \mathrm { CH } _ { 2 } - \mathrm { SH }$

A) compound (a)
B) compound (b)
C) compound (c)
D) compound (d)
E) compound (e)f.
compound (f)

Question 6

Complete the reaction by giving the missing product.

Question 7

Draw the correct product for each of the reactions:

Question 8

Complete the reaction by giving the major organic product(s).

Question 9

Consider this addition polymer, called poly(methyl methacrylate). What is the structure of the monomer from which this polymer is formed by free-radical alkene polymerization?

Question 10

Complete the reactions by giving the structure of the missing organic products.

Question 11

Complete the reaction by giving the structures of all products.

Question 12

Provide the structures of the missing compounds.

Question 13

Which of these compounds is capable of spontaneously providing a free-radical RO• that can initiate free-radical chain reactions?

A) HO-OH
B) (CH₃)₃O-OC(CH₃)₃
C) (CH₃)₃-O-C(CH₃)₃
D) (CH₃)₃O-OH
E) All can serve as initiators.

Question 14

Free-radical polymerization of ethylene proceeds with the following propagation steps.
It turns out that polyethylene made by free-radical polymerization contains some branches, for example,
(a) Give a plausible mechanism, complete with "fishhooks," for propagation steps that can account for formation of these branches.
(b) It is possible (by a completely different method) to form polyethylene with unbranched chains. Which do you think would have higher density, branched-chain polyethylene or polyethylene with unbranched chains? Explain briefly.

Question 15

Devise a synthesis to achieve the transformation.

Question 16

1-Methyl-1-vinyl cyclopentane undergoes addition of HBr under two different conditions as shown in the two pathways. A mixture of products is obtained in Pathway A, whereas a single product is obtained in pathway

Question 17

A free-radical addition of a certain compound X-Y to an alkene (R = alkyl) results in the conversion:
The first propagation step in the mechanism is
Therefore, what is the second propagation step in the mechanism?

A)

B)

C)
$$\mathrm { X } - \mathrm { Y } \longrightarrow \mathrm { Y } \cdot + \cdot \mathrm { X }$$
D) Both (b) and (c) are propagation steps.
E) Both (a) and (b) are propagation steps.

Question 18

Outline a multi-step synthesis of 4-octanone from 1-pentyne and any other reagents. (Show the reagents required for each step, and the product of each step. Don't show the mechanism.)

Question 19

Complete the reactions by giving the structure of the missing organic products.

Question 20

Complete the reactions by giving the structure of the missing organic products.

Question 21

Identify the stereochemistry of the polymers.

Question 22

Predict the major organic product of the reaction:

Question 23

Outline a synthesis for the alkyne using acetylene and any reagents three carbons or less.

Question 24

Outline a synthesis of this product.

Question 25

Provide the major organic product for the reaction.