10. Addition Reactions

Predict the major product when each reagent reacts with ethylene oxide.

(a) NaOCH₂CH₃ (sodium ethoxide)

(b) NaNH₂ (sodium amide)

(c) NaSPh (sodium thiophenoxide)

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.

Three arene oxides can be obtained from phenanthrene.

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

a. Propose a mechanism for the conversion of cis-hex-3-ene to the epoxide (3,4-­epoxyhexane) and the ring-opening reaction to give the glycol, hexane-3,4-diol. In your mechanism, pay particular attention to the stereochemistry of the intermediates and products.

b. Repeat part (a) for trans-hex-3-ene. Compare the products obtained from cis- and trans-hex-3-ene. Is this reaction sequence stereospecific?

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.]

Under the right conditions, the following acid-catalyzed double cyclization proceeds in remarkably good yields. Propose a mechanism. Does this reaction resemble a biological process you have seen? 

The reactivity of cyclopropanes often mimics that of alkenes.

(a) On the basis of this, suggest a mechanism for the following reaction.

The reactivity of cyclopropanes often mimics that of alkenes.

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

In light of your answer to Assessment 9.47, predict the product of the following reactions we have seen previously where an alcohol is substituted for water.

(a)

What is the major product obtained from the reaction of 2-ethyloxirane with each of the following reagents?

d. CH₃OH/CH₃O^-

Predict the products of the following reactions.

(j)

(k)

(l)

What stereoisomers are obtained from the reaction of the alkenes in [PROBLEM 10-32] with a peroxyacid ­followed by reaction with hydroxide ion?

a. trans-2-butene

b. cis-2-butene

Show the rest of the mechanism for formation of the cyclized intermediate in Figure 14-6.

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