8_all_ - 8.1 Give the structure and name of the product...

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8.1 Give the structure and name of the product that would be obtained from the ionic addition of IBr to propene. Answer: IB r I Br Br I 8.3 Provide mechanistic explanations for the following observations :( a The addition of hydrogen chloride to 3-methyl-1-butene produces two products 2-chloro-3-methylbutane and 2-chloro-2-methylbutane. (b) The addition of hydrogen chloride to 3,3-dimethyl-1-butene produces two products: 3-chloro-2,2-dimethylbutane and 2-chloro-2,3-dimethylbutane. (The first explanations for the course of both of these reactions were provide by F. Whitmore; see Section 7.7A.) Answer: (a) step 1: H + C + ; C + C + Because the C + much more stable then the C + step 2: C + + Cl - ; C + + Cl + Me Cl
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(b) step 1: H + C + rearrangement: C + C + Because the C + much more stable then the C + Step 2: C + + Cl - Cl ; C + + Cl - Me Cl 8.4 In one industrial synthesis of ethanol, ethene is first dissolved in 95% sulfuric acid. In a second step water is added and the mixture is heated. Outline the reactions involved. Answer: H OSO 3 H OH 8.6 Outline all steps in a mechanism showing how 2,3-dimethyl-2-butanol is formed in the acid-catalyzed hydration of 3,3-dimethyl-1-butene. Answer:
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H 3 C C CH 3 CH 3 C H CH 2 + H O H H slow H 3 C C CH 3 CH 3 H C CH 3 + OH H STEP 1 STEP2 H 3 C C CH 3 3 H C 3 H 3 C C 3 H C 3 3 FAST (Rearrangement) STEP3 H 3 C C H 3 C H C 3 3 O H H + H 3 C C H 3 C H C 3 3 O H H STEP4 H 3 C C H 3 C H C CH 3 CH 3 O H H O H H + FAST H 3 C C H 3 C H C 3 3 HO + H O H H 8.7 The following order of reactivity is observed when the following alkenes are subjected to acid-catalyzed hydration. (H 3 C) 2 CC H 2 > H 3 CHC CH 2 > H 2 H 2 Explain this order of reactivity. Answer: The mechanism of hydration is to form carbocation. For the stability of the carboation is: CH 3 (H 3 C) 2 C > H 3 CHC CH 3 > H 2 C CH 3 So the CH 3 (H 3 C) 2 C is the most stable, has the lowest energy, and the (H 3 C) 2 H 2 has the highest reactivity. And the H 2 H 2 has the lowest reactivity. 8.8 When 2-methylpropene (isobutylene) is dissolved in methanol containing a strong acid, a reaction takes place to produce tert- butyl methyl ether, CH 3 OC (CH 3 ) 3 . Write a mechanism that accounts for this.
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Answer: H 2 C C CH 3 CH 3 H + + C+ H 3 C CH 3 CH 3 C+ H 3 C CH 3 CH 3 + OC H 3 H C H 3 C CH 3 CH 3 O + H CH 3 C H 3 C CH 3 CH 3 O + H CH 3 + A - C H 3 C CH 3 CH 3 O CH 3 8.9 In section 8.7 you studied a mechanism for the formation of one enantiomer of trans -1, 2-dibromocyclopentane when bromine adds to cyclopentene. Now write a mechanism showing how the other enantionmer forms. Br 2 Br + Br - Br Br 8.10 Outline a mechanism that account for the formation of trans -2-bromocyclopentanol and its enantiomer when cyclopentene is treated with an aqueous solution of bromine. Br H 2 O + OH Br Br OH 8.11 When ethene gas is passed into an aqueous solution containing bromine and sodium chloride, the products of the reaction are BrCH 2 CH 2 Br, BrCH 2 CH 2 OH, and BrCH 2 CH 2 Cl. Write
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mechanisms showing each product is formed; Answer: Step1: H 2 CC H 2 Br Br + _ Br + Step2: Br + Br Br H H H H Br + Cl Cl H H Br H H Br + H 2 O OH 2 H H Br H H
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OH 2 H H Br H H H 2 O H H Br H H + + H 3 O 8.12 What products would you expect from each of the following reactions?
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8_all_ - 8.1 Give the structure and name of the product...

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