10. Addition Reactions

What alkene should be used to synthesize each of the following alkyl bromides?

c.

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?

What alkene should be used to synthesize each of the following alkyl bromides?

b.

Of the possible products shown for the following reaction, are there any that will not be formed?

When 3-methyl-1-butene reacts with HBr, two alkyl halides are formed: 2-bromo-3-methylbutane and 2-bromo-2-methylbutane. Propose a mechanism that explains the formation of these two products.

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) Based on what you know about the relative stabilities of alkyl cations and benzylic cations, predict the product of addition of HBr to 1-phenylpropene.

(b) Propose a mechanism for this reaction.

At the beginning of Chapter 9, we stated that after finishing Chapters 8 and 9, we would have the ability to make a large variety of functional groups using related reactions. Show the reagent(s) necessary to convert 1-isobutylcyclohexene into the following molecules.

(a)

What is the major product obtained from the addition of HBr to each of the following compounds?

e.

f.

A wayward chemist proposed the following mechanism for the addition of HBr to an alkene.

(a) Why is this mechanism unlikely?

(b) Compare the reaction coordinate diagrams for the actual mechanism studied in Section 8.3.1 and this alternate mechanism on the same graph.

What will be the product of the preceding reaction if HBr is used in place of Br₂?

Predict the product and provide a mechanism for the reaction of 1-methylcyclohexene with HBr.

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

(k)

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

(b)