What characteristics must the reactant of a stereospecific reaction have?

a. Is the reaction of 2-butene with HBr regioselective?

b. Is it stereoselective?

c. Is it stereospecific?

d. Is the reaction of 1-butene with HBr regioselective?

e. Is it stereoselective?

f. Is it stereospecific?

What stereoisomers are obtained from each of the following reactions?

b.

a. What stereoisomers are formed in the following reaction? Are they enantiomers or diastereomers?

b. Which stereoisomer is formed in greater yield?

a. What alkene is required to synthesize each of the following compounds?

b. What other epoxide is formed in each synthesis?

c. Assign an R or S configuration to each asymmetric center.

1.

a. What alkene is required to synthesize each of the following compounds?

b. What other epoxide is formed in each synthesis?

c. Assign an R or S configuration to each asymmetric center.

2.

What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.

a. cyclohexene

b. 1-ethylcyclohexene

What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.

c. cis-2-butene

What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.

d. (Z)-3,4-dimethyl-3-hexene

The reaction of 2-ethyl-1-pentene with Br₂, with H₂ + Pd/C, or with R₂BH/THF followed by aqueous HO^- + H₂O₂ leads to a racemic mixture. Explain why a racemic mixture is obtained in each case.

Using a sample of trans-2-pentene, how could you prove that the addition of Br₂ forms a cyclic bromonium ion intermediate rather than a carbocation intermediate?

What stereoisomers are obtained from the following reactions?

c. (E)-3-methyl-2-pentene + HBr

d. cis-3-hexene + HBr

When Br₂ adds to a cis alkene that has different substituents attached to each of the two sp² carbons, such as cis-2-heptene, identical amounts of the two threo enantiomers are obtained even though Br^- is more likely to add to the less sterically hindered carbon of the bromonium ion. Explain why identical amounts of the two enantiomers are obtained.

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

c.

d.

a. What is the major product obtained from the reaction of propene and Br₂ plus excess Cl^-?

b. Indicate the relative amounts of the stereoisomers that are obtained.

What is the product of the reaction of maleate and H₂O when H₂SO4 is used as a catalyst instead of fumarase?

Show how each of the following compounds can be synthesized from an alkene:

a.

Show how each of the following compounds can be synthesized from an alkene:

b.

Show how each of the following compounds can be synthesized from an alkene:

c.

Explain why 3-methylcyclohexene should not be used as the starting material in Problem 52b.

Which electrophilic addition reactions

a. form a carbocation intermediate? intermediate?

Which electrophilic addition reactions

c. form a three-membered ring

Which electrophilic addition reactions

d. form a five-membered ring intermediate?

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

a.

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

b.

Identify the electrophile and the nucleophile in each of the following reaction steps and then draw curved arrows to illustrate the bond-making and bondbreaking processes.

c.

What is the major product of the reaction of 2-methyl-2-butene with each of the following reagents?

a. HBr

What is the major product of the reaction of 2-methyl-2-butene with each of the following reagents?

b. HI

What is the major product of the reaction of 2-methyl-2-butene with each of the following reagents?

d. O₃, −78 °C, followed by (CH₃)₂S