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For the addition of HCl to alkenes according to the general equation given in the preceding problem, assume the mechanism involves rate-determining formation of the more stable carbocation (arrow 5 ) and predict the alkyl chloride formed by reaction of HCl with (CH 3)2C=CH2

a. (CH3)2CHCH2Cl

b. (CH3)3CCl 

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The overall equation for the addition of HCl to alkenes is:  

 If the transition state for proton transfer from HCl to the alkene (arrow  5 ) resembles a carbocation and this step is rate-determining, what should be the effect of alkene structure on the rate of the overall reaction?

 Fastest rate                                    Slowest rate

A. H2C=CH2    CH3CH=CHCH3    (CH3)2C=C(CH3)2

B. CH3CH=CHCH3    (CH3)2C=C(CH3)2    H2C=CH2

C. CH3CH=CHCH3    H2C=CH2    (CH3)2C=C(CH3)2

D. (CH3)2C=C(CH3)2    CH3CH=CHCH3    H2C=CH2

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What term best describes the relationship between an alkene and a carbocation?  

a. Isomers

b. Resonance contributors 

c. Alkene is conjugate acid of carbocation

d. Alkene is conjugate base of carbocation

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Based on the E1 mechanism for the conversion of a tertiary alkyl chloride to an alkene as summarized in arrows 3 and 4, which arrow(s) correspond(s) to exothermic processes? 

a. Arrow 3

b. Arrow 4

c. Both 3 and 4

d. Neither 3 nor 4

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Based on the E1 mechanism for the conversion of a tertiary alkyl chloride to an alkene as summarized in arrows 3 and 4, which arrow(s) represent(s) more than one elementary step? 

a. Arrow 3

b. Arrow 4

c. Both 3 and 4

d. Neither 3 nor 4

 

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Based on the E1 mechanism for the acid-catalyzed dehydration of a tertiary alcohol as summarized in arrows 1 and 4, which arrow(s) represent(s) more than one elementary step?

a. Arrow 1

b. Arrow 4

c. Both 1 and 4

d. Neither 1 nor 4

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Based on the SN1 mechanism for the reaction of tertiary alcohols with HCl as summarized in arrows 1 and 2, which arrow(s) represent(s) more than one elementary step? 

a. Arrow 1

b. Arrow 2

c. Both 1 and 2

d. Neither 1 nor 2

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Acid-catalyzed dehydration of 2,2-dimethyl-1-hexanol gave a number of isomeric alkenes including 2-methyl-2-heptene as shown in the following equation.

(a) Write a stepwise mechanism for the formation of 2-methyl-2-heptene, using curved arrows to show the fl ow of electrons.

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In Problem 5.20 (Section 5.13) we saw that acid-catalyzed dehydration of 2,2- dimethylcyclohexanol afforded 1,2-dimethylcyclohexene. To explain this product we must write a mechanism for the reaction in which a methyl shift transforms a secondary carbocation to a tertiary one. Another product of the dehydration of 2,2-dimethylcyclohexanol is isopropylidenecyclopentane. Write a mechanism to rationalize its formation, using curved arrows to show the flow of electrons. 

 

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Write a sequence of steps depicting the mechanisms of each of the following reactions. Use curved arrows to show electron flow.

 

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Write a sequence of steps depicting the mechanisms of each of the following reactions. Use curved arrows to show electron flow.

 

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Write a sequence of steps depicting the mechanisms of each of the following reactions. Use curved arrows to show electron flow.  

 

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In the acid-catalyzed dehydration of 2-methyl-1-propanol, what carbocation would be formed if a hydride shift accompanied cleavage of the carbon–oxygen bond in the alkyloxonium ion? What ion would be formed as a result of a methyl shift? Which pathway do you think will predominate, a hydride shift or a methyl shift?

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You have available 2,2-dimethylcyclopentanol (A) and 2-bromo-1,1-dimethylcyclopentane (B) and wish to prepare 3,3-dimethylcyclopentene (C). Which would you choose as the more suitable reactant, A or B, and with what would you treat it? 

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Menthyl chloride and neomenthyl chloride have the structures shown. One of these stereoisomers undergoes elimination on treatment with sodium ethoxide in ethanol much more readily than the other. Which reacts faster, menthyl chloride or neomenthyl  chloride? Why?

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The rate of the reaction

(CH3)3 CCl + NaSCH2CH3 → (CH3)2C=CH2 + CH3CH2SH + NaCl

is first-order in (CH3)3CCl and first-order in NaSCH2CH3 . Give the symbol (E1 or E2) for the most reasonable mechanism, and use curved arrows to show the flow  of electrons.  

 

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter.

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter.

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter.

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter.

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter. 

 

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter. 

 

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Predict the major organic product of each of the following reactions. In spite of the structural complexity of some of the starting materials, the functional group transformations are all of the type described in this chapter.
 

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Give the structures of two different alkyl bromides both of which yield the indicated alkene as the exclusive product of E2 elimination.
 

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Give the structures of two different alkyl bromides both of which yield the indicated alkene as the exclusive product of E2 elimination.
 

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