One of the principal components of lemongrass oil is limonene, C₁₀H₁₆. When limonene is treated with excess hydrogen and a platinum catalyst, the product is an alkane of ­formula C₁₀H₂₀. What can you conclude about the structure of limonene?

How many different alkenes can be hydrogenated to form

a. butane?

b. 3-methylpentane?

What alkene would you start with if you wanted to synthesize

a. pentane?

Draw the products of the following reactions. If the products can exist as stereoisomers, show which stereoisomers are formed.

i. (Z)-3,4-dimethyl-3-heptene + H₂, Pd/C

What stereoisomers would you expect to obtain from each of the following reactions?

c.

d.

A graduate student was studying enzymatic reductions of cyclohexanones when she encountered some interesting chemistry. When she used an enzyme and NADPH to reduce the following ketone, she was surprised to find that the product was optically active. She carefully repurified the product so that no enzyme, NADPH, or other contaminants were present. Still, the product was optically active.

c. If this reaction could be accomplished using H₂ and a nickel catalyst, would the product be optically active? Explain.

Retrosynthetic analysis is the process of working backward to develop the synthesis of a new compound. In Chapter 10, we begin developing multistep syntheses in this manner. For now, try to work backward a single step by suggesting an alkene and a reagent that would give products (a)–(i). [Your answers should not include alkenes that undergo rearrangement to give the desired products.]

(b)

Draw the products of the following reactions, including their configurations:

Show how you would accomplish the following transformations. You may use any additional reagents you need.

(d)