10. Addition Reactions

Propose mechanisms consistent with the following reactions.

(f)

When 1,2-epoxycyclohexane (cyclohexene oxide) is treated with anhydrous HCl in methanol, the principal product is trans-2-methoxycyclohexanol. Propose a mechanism to account for the formation of this product.

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)

The existence of the NIH shift was established by determining the major product obtained from rearrangement of the following arene oxide, in which a hydrogen has been replaced by a deuterium.

a. What would be the major product if the NIH shift occurs? (Hint: A C—H bond is easier to break than a C—D bond.)

Draw the mechanism for formation of the two addition products.

Propose a mechanism for each of the following reactions:

b.

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

d. CH₃OH/CH₃O^-

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

c. 0.1MNaOH

Write the appropriate reagent over each arrow.

Two stereoisomers are obtained from the reaction of cyclopentene oxide and dimethylamine. The R,R-isomer is used in the manufacture of eclanamine, an antidepressant. What other isomer is obtained?

Predict the product of the following reactions.

(a)

Predict the major products of the following reactions, including stereochemistry where appropriate.

a. 2,2-dimethylxirane + H⁺/H₂¹⁸O (oxygen labeled water)

b. 2,2-dimethylxirane + H¹⁸O^–/H₂¹⁸O (oxygen labeled water)

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

(a) NaOCH₂CH₃ (sodium ethoxide)

(b) NaNH₂ (sodium amide)

(c) NaSPh (sodium thiophenoxide)

Predict the products of the following reactions.

(m)

(n)

Working backward, design a synthesis of the following alcohol using two different epoxide/Grignard reagent combinations.