BackIn the presence of an acid catalyst, acetaldehyde forms a trimer known as paraldehyde. Because it induces sleep when it is administered to animals in large doses, paraldehyde is used as a sedative or hypnotic. Propose a mechanism for the formation of paraldehyde.
The chlorination of pentane gives a mixture of three monochlorinated products.
a. Draw their structures.
Show how you would prepare cyclopentene from each compound.
c. cyclopentane (not by dehydrogenation)
If cyclopentane reacts with more than one equivalent of Cl2 at a high temperature, how many dichlorocyclopentanes would you expect to obtain as products?
Suggest a mechanism for the following reactions.
(a)
How many alkyl chlorides are obtained from monochlorination of the following alkanes? Disregard stereoisomers.
g.
Each of the following proposed mechanisms for the free-radical chlorination of methane is wrong. Explain how the experimental evidence disproves each mechanism.
b.
Write the initiation, propagation, and termination steps for the monochlorination of cyclohexane.
What hydrocarbon with the same molecular formula as in part a forms three monochlorinated products? One is achiral and two are chiral.
What are the answers to Problem 29 when the same compounds are treated with Br2 at 125 °C?
c.
Because of the angle strain present in cyclopropanes, they tend to open up in the presence of nearby radicals. Show a mechanism for the following reaction that demonstrates this principle.
Predict the product(s) of the following halogenation reactions. Only one equivalent of the halogen is used in each case. If the reaction proceeds selectively, indicate this by only drawing the major product. If the reaction is not selective, draw all possible products.
(f)
Predict the major product of the following bromination reactions.
(c)
What are the product(s) of each of the following reactions? Disregard stereoisomers.
f.
We have studied the following reactions in previous chapters. For each, (i) indicate which reaction sheets they should appear on, (ii) show the best structure to use to represent them, and (iii) write the notes you could put in the margin so that the mechanism is implied.
(b) Radical halogenation of an alkane