a. How could each of the following compounds be prepared from a hydrocarbon in a single step?

b. What other organic compound would be obtained from each synthesis?

1.

a. How could each of the following compounds be prepared from a hydrocarbon in a single step?

b. What other organic compound would be obtained from each synthesis?

2.

Draw the products obtained from the reaction of one equivalent of HBr with one equivalent of 1,3,5-hexatriene.

a. Which product(s) will predominate if the reaction is under kinetic control?

b. Which product(s) will predominate if the reaction is under thermodynamic control?

How would the following substituents affect the rate of a Diels–Alder reaction?

a. an electron-donating substituent in the diene

How would the following substituents affect the rate of a Diels–Alder reaction?

b. an electron-donating substituent in the dienophile

How would the following substituents affect the rate of a Diels–Alder reaction?

c. an electron-withdrawing substituent in the diene

The acid dissociation constant (K_a) for loss of a proton from cyclohexanol is 1 × 10^–16.

a. Draw a reaction coordinate diagram for loss of a proton from cyclohexanol.

Draw the resonance contributors for phenol.

Draw the resonance contributors for the phenolate ion.

e. Which has a greater Ka: cyclohexanol or phenol?

f. Which is a stronger acid: cyclohexanol or phenol?

Protonated cyclohexylamine has a Ka = 1 * 10-11. Using the same sequence of steps as in Problem 94, determine which is a stronger base: cyclohexylamine

or aniline.

e. Which has a greater Ka: cyclohexylammmonium ion or anilinium ion?

f. Which is a stronger acid: cyclohexylamine or aniline?

Which dienophile in each pair is more reactive in a Diels–Alder reaction?

1.

Which dienophile in each pair is more reactive in a Diels–Alder reaction?

2.

Draw the major products obtained from the reaction of one equivalent of HBr with the following compounds. For each reaction, indicate the kinetic product and the thermodynamic product.

b.

Cyclopentadiene can react with itself in a Diels–Alder reaction. Draw the endo and exo products.

Which diene and which dienophile could be used to prepare each of the following?

e.

Propose a mechanism for the following reaction:

What is the product of the following reaction?

What are the products of the following reaction?

How many stereoisomers of each product could be obtained?

As many as 18 different Diels–Alder products can be obtained by heating a mixture of 1,3-butadiene and 2-methyl-1,3-butadiene. Identify the products.

On a single graph, draw the reaction coordinate diagram for the addition of one equivalent of HBr to 2-methyl-1,3-pentadiene and for the addition of one equivalent of HBr to 2-methyl-1,4-pentadiene. Which reaction is faster?

While attempting to recrystallize maleic anhydride, a student dissolved it in freshly distilled cyclopentadiene rather than in freshly distilled cyclopentane. Was her recrystallization successful?

In 1935, J. Bredt, a German chemist, proposed that a bicycloalkene could not have a double bond at a bridgehead carbon unless one of the rings contains at least eight carbons. This is known as Bredt's rule. Explain why there cannot be a double bond at this position.

The experiment shown next and discussed in Section 8.13 shows that the proximity of the chloride ion to C-2 in the transition state causes the 1,2-addition product to form more rapidly than the 1,4-addition product.

a. Why was it important for the investigators to know that the preceding reaction was being carried out under kinetic control?

Identify the product of the following reaction.

Draw the resonance contributors of the cyclooctatrienyl dianion.

a. Which of the resonance contributors is the least stable?

Draw the resonance contributors of the cyclooctatrienyl dianion.

b. Which of the resonance contributors makes the smallest contribution to the hybrid?