10. Addition Reactions

Predict the product of the following epoxide addition reactions.

(b)

Predict the product of the following epoxide addition reactions.

(a)

In Chapter 13, we learned that epoxide opening can give different products, depending on whether the reaction occurs under acidic or basic conditions. Explain why the epoxide shown opens identically under either set of conditions.

In Chapter 13, we discuss the ring-opening reactions of epoxides, such as the one shown here.

(a) Based on the bonds formed and the bonds broken, calculate ∆H°.

Chapter 8 discussed the synthesis of cholesterol, which proceeds by a cationic cyclization cascade. Without looking back, suggest a mechanism by which the following reaction occurs. [The carbons have been numbered for you.]

Despite it being equally favorable, opening of the epoxide does not happen in the absence of an acid catalyst. How does acid make the reaction faster? Demonstrate this concept by directly comparing the reaction coordinate diagram for both situations A and B.

The reactivity of cyclopropanes often mimics that of alkenes.

(b) Besides opening the three-membered ring, what is the driving force for this reaction?

Suggest mechanisms for the following reactions, which are similar to the mechanism we saw for lanosterol biosynthesis at the end of Chapter 8.

(a)

Suggest mechanisms for the following reactions, which are similar to the mechanism we saw for lanosterol biosynthesis at the end of Chapter 8.

(b)

Three arene oxides can be obtained from phenanthrene.

a. Draw the structures of the three phenanthrene oxides.

Ethylene oxide reacts readily with HO^- because of the strain in the three-membered ring. Explain why cyclopropane, a compound with approximately the same amount of strain, does not react with HO^-.

Propose a mechanism for each of the following reactions:

a.

Three arene oxides can be obtained from phenanthrene.

d. Which of the three phenanthrene oxides is most likely to be carcinogenic?

How do the major products obtained from rearrangement of the following arene oxides differ?

What products are obtained from the reaction of cyclohexene oxide with

a. methoxide ion?