10. Addition Reactions

How does the first step in the reaction of propene with Br₂ differ from the first step in the reaction of propene with HBr?

What stereoisomers are obtained when (S)-3-methyl-1-pentene reacts with Cl₂?

Predict the product(s) of each of the following reactions, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.

(b)

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂ (ii) Cl₂

(f)

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

c.

What is the product of the addition of I—Cl to 1-butene? (Hint: Chlorine is more electronegative than iodine [Table 1.3].)

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ii) Cl₂

(h)

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂

(k)

Using cyclooctyne as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.)

(a) cis-cyclooctene

(b) cyclooctane

(c) trans-1,2-dibromocyclooctane

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂

(h)

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

b.

Cyclohexene is dissolved in a solution of lithium chloride in chloroform. To this solution is added one equivalent of bromine. The material isolated from this reaction contains primarily a mixture of trans-1,2-dibromocyclohexane and trans-1-bromo-2-chlorocyclohexane. Propose a mechanism to show how these compounds are formed.

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂ (ii) Cl₂.

(e)

Draw the product or products that will be obtained from the reaction of cis-2-butene and trans-2-butene with each of the following reagents. If a product can exist as stereoisomers, show which stereoisomers are formed.

4. Br₂ in CH₂Cl₂

Using 1,2-dimethylcyclohexene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.) If a chiral product is shown, assume that it is part of a racemic mixture.

(c)