10. Addition Reactions

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H₂, Pd/C; and (x) D₂ , Pd/C.

(e)

Because deuterium behaves like hydrogen in chemical reactions yet is detected differently, chemists use the incorporation of deuterium to better understand the subtleties of reaction mechanisms. Deuterium is incorporated by replacing H₂ with D₂ in the hydrogenation reaction. Identify the product expected when the alkenes in Assessment 9.34 react with D₂ and Pd/C. [Don't worry about showing all diastereomers.]

How many different alkenes can be hydrogenated to form

a. butane?

b. 3-methylpentane?

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.

On a per alkene basis, which would have the more negative heat of hydrogenation?

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ix) H₂, Pd/C;

(d)

Give the expected major product for each reaction, including stereochemistry where applicable.

(c)

(d)

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

j. (E)-2,3-dichloro-2-butene + H₂, Pd/C

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)

What product results when the following molecules are treated with H₂ Pd/C? Be sure to indicate the relative stereochemical outcome. Draw both enantiomers of any racemic mixtures. [It is difficult to control the stoichiometry of gases so there is enough H₂ to reduce all alkenes.]

(b)

What are the products of the following reactions? Indicate whether each reaction is an oxidation or a reduction.

b.