10. Addition Reactions

What is the major product of each of the following reactions?

2.

What is the major product of each of the following reactions?

1.

a. Identify two alkenes that react with HBr to form 1-bromo-1-methylcyclohexane without undergoing a carbocation rearrangement.

b. Would both alkenes form the same alkyl halide if DBr were used instead of HBr? (D is an isotope of H, so D⁺ reacts like H⁺.)

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.

1. HCl

A student was about to turn in the products he had obtained from the reaction of HI with 3,3,3-trifluoropropene when he realized that the labels had fallen off his flasks and he did not know which label belonged to which flask. His friend reminded him of the rule that says the electrophile adds to the sp² carbon bonded to the most hydrogens. In other words, he should label the flask containing the most product 1,1,1-trifluoro-2-iodopropane and label the flask containing the least amount of product 1,1,1-trifluoro-3-iodopropane. Should he follow his friend’s advice?

a. What product is obtained from the reaction of HCl with 1-butene? With 2-butene?

b. Which of the two reactions has the greater free energy of activation?

c. Which compound reacts more rapidly with HCl: (Z)-2-butene or (E)-2-butene?

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.

Predict the major products of the following reactions, and give the structures of any intermediates. Include stereochemistry where appropriate.

(a)

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

b. 2-methylpropene + HCl

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 of each of the following reactions, assuming that one equivalent of each reagent is used in each reaction?

c.

Predict the product(s) of each of the following reactions. If you expect a racemic mixture, draw both enantiomers.

(c)

Suggest an alkene that, upon reaction with the appropriate hydrohalic acid, will produce only the alkyl halide shown. [Ignore stereochemistry.]

(b)

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

(d)

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