10. Addition Reactions

What products are obtained from the reaction of cyclohexene oxide with

a. methoxide ion?

There are two mechanisms by which each of the two enantiomers can form in the reaction shown in Figure 9.37. Show them.

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Propose mechanisms consistent with the following reactions.

(g)

The following reaction resembles the acid-catalyzed cyclization of squalene oxide. Propose a mechanism for this reaction.

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?

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

c. 0.1MNaOH

Propylene oxide is a chiral molecule. Hydrolysis of propylene oxide gives propylene glycol, another chiral molecule.

(a) Draw the enantiomers of propylene oxide.

(b) Propose a mechanism for the acid-catalyzed hydrolysis of pure (R)-propylene oxide.

Propose a mechanism for each of the following reactions:

b.

Limonene is one of the compounds that give lemons their tangy odor. Show the structures of the products expected when limonene reacts with an excess of each of these reagents.

f. peroxyacetic acid in acidic water

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.

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)

What products are obtained from the reaction of cyclohexene oxide with

b. methylamine?

Write the appropriate reagent over each arrow.

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

(b)

Draw the mechanism for formation of the two addition products.