10. Addition Reactions

What is the major product obtained from the reaction of HBr with each of the following?

a.

Predict the major products of the following reactions, and propose mechanisms to support your predictions.

a. pent-1-ene + HCl

What is the major product obtained from the reaction of HBr with each of the following?

b.

Which of the following alkenes would you expect to react fastest with HBr in each pair?

(b)

Imagine an electrophilic addition where the first step is exothermic. Which carbocation—2°, 3°, or neither—would you expect to form preferentially? Explain.

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

b. Is it stereoselective?

c. Is it stereospecific?

Would you expect but-2-ene or 2-methylbut-2-ene to react more quickly with HBr?

What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?

(e)

When 1-chlorocyclohexene reacts with HBr, the major product is 1-bromo-1-chlorocyclohexane. Propose a mechanism for this reaction, and explain why your proposed intermediate is more stable than the other possible intermediate

Draw the mechanism for the reaction of cyclohexene with HCl

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

b. HI

Which of the following compounds reacts with HBr more rapidly?

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

h. cis-2-butene + HBr

When HBr adds across the double bond of 1,2-dimethylcyclopentene, the product is a mixture of the cis and trans isomers. Show why this addition is not stereospecific.