chapter 6

Organic Chemistry, 8e (Bruice) Chapter 6 The Reactions of Alkenes - The Stereochemistry of Addition Reactions Complete the following reaction and provide a detailed, step-by-step mechanism for the process. Answer: Section: 6-1 Draw the product. Answer: Section: 6-1 3) Provide the structure of the major organic product in the reaction below. Answer: Section: 6-1 Provide the structure of the major organic product in the reaction below. Answer: Section: 6-1 5) Which of the following is the most stable carbocation? I II III IV V Answer: D Section: 6-2 6) Which of the following alkenes reacts with HCl at the slowest rate? A) 96139021463000B) C) 96139022860000D) E) Answer: A Section: 6-4 7) What is hyperconjugation, and how does it affect carbocation stability? Answer: Delocalization of electrons by the overlap of a ? bond with an empty p orbital is hyperconjugation. This effect occurs only when the interacting orbitals are properly aligned. The more alkyl groups which are substituents of a cationic carbon, the more the cation can be stabilized by the delocalizing hyperconjugation effects. Section: 6-2 8) Identify the most stable carbocation. 462992815367000A) B) C) D) E) Answer: C Section: 6-2 9) Which alkene reacts the fastest with HBr? A) B) C) D) E) Answer: E Section: 6-4 According to the Hammond Postulate, which of the following is correct? The transition state of an endothermic reaction step will be more reactant-like than product- like. The intermediate of an endothermic reaction step will be more reactant-like than product-like. The transition state of an exothermic reaction step will be more reactant-like than product- like. All transition states are more product-like than reactant-like. All transition states are more reactant-like than product-like. Answer: C Section: 6-3 11) Which of the following compounds will react most rapidly with HCl? 5-methyl-1-hexene 4-methyl-1-hexene (E)-5-methyl-2-hexene (E)-2-methyl-3-hexene 2-methyl-2-hexene Answer: E Section: 6-4 For an endergonic reaction step, the Hammond postulate allows one to say that the transition state of the step resembles the reactants of the step. the transition state of the step resembles the products of the step. the step is rate-determining since it has the smallest Ea. the reaction containing this step is overall first order. the transition state is precisely symmetric with bond-breaking and bond-forming occurring to the same extent. Answer: B Section: 6-3 Based on the relative stabilities of the intermediates involved, explain the basis for Markovnikov's rule in the addition of hydrogen halides to alkenes. Answer: The rate-determining step in this reaction is the production of a carbocation intermediate. Since this step is endothermic, Hammond's postulate allows one to gauge the relative stabilities of the transition states by comparing the relative stabilities of the carbocation intermediates. The reaction pathway which produces the more substituted carbocation will thus occur more rapidly. Section: 6-4 Which statement(s) are true according to the Hammond postulate? In an exergonic reaction, the transition state is more similar in energy to the reactant than the product. In an exergonic reaction, the transition state is more similar in energy to the product than the reactant. In an endergonic reaction, the transition state is more similar in energy to the reactant than the product. In an endergonic reaction, the transition state is more similar in energy to the product than the reactant. A and D B and C Answer: E Section: 6-3 15) Draw the major organic product generated in the reaction below. Answer: Section: 6-4 Draw the major organic product generated in the reaction below. Answer: Section: 6-4 Draw the major organic product generated in the reaction below. 96139021971000Answer: Section: 6-4 18) Draw the major organic product generated in the reaction below. Answer: Section: 6-4 Draw the major organic product generated in the reaction below. Answer: Section: 6-4 Draw the major organic product generated in the reaction below. 93535525082500Answer: Section: 6-4 Draw the structures of the two alkenes that react with HBr to yield 1-bromo-1- methylcyclopentane as the major organic product. Answer: Section: 6-4 Which is more highly regioselective the addition of HCl to methylenecyclohexane or to 1- methylcyclohexene? Explain. Answer: Addition to methylenecyclohexane is more highly regioselective. There is a greater difference in the activation energies leading to a primary and tertiary carbocation than in the activation energies leading to a secondary and tertiary carbocation. Section: 6-4 Provide the major organic product(s) in the reaction below. Answer: 395032732849600 Section: 6-4 24) What is the major product of the following reaction? I II III IV V Answer: C Section: 6-5 MCAT: 8.1 What is the major product from the acid-catalyzed hydration of 2-methyl-2-pentene? 2-methylpentane 2-methyl-1-pentanol 2-methyl-2-pentanol 2-methyl-3-pentanol 1-methoxypentane Answer: C Section: 6-5 26) Draw the major organic product generated in the reaction below. Answer: Section: 6-5 Draw the major organic product generated in the reaction below. 942975220765Answer: Section: 6-5 931162220036Draw the major organic product generated in the reaction below. Answer: Section: 6-5 Complete the following reaction and provide a detailed, step-by-step mechanism for the process. Answer: Section: 6-5 Provide the structure of the major organic product of the following reaction. 959094255291Answer: Section: 6-5 Identify the true statements in the mechanism in the addition of water to an alkene. The addition of the electrophile is a slow step. The addition of the nucleophile is a fast step. A carbocation is formed as an intermediate. Water abstracts the extra proton from the protonated alcohol. all of the above Answer: E Section: 6-5 32) Provide the structure of the major organic product in the reaction below Answer: Section: 6-5 Draw the product. Answer: Section: 6-5 Provide the structure of the major organic product of the following reaction. Answer: Section: 6-6 Give the product for the reaction of 1-butene with methanol in the presence of acid. 1-ethoxybutane 2-ethoxybutane 1-methoxybutane 2-methoxybutane 1-butanol Answer: D Section: 6-6 Draw the product. Answer: Section: 6-6 Provide the structure of the major organic product in the reaction below. Answer: Section: 6-6 38) Propose a mechanism for the following reaction: Answer: Section: 6-7 39) Provide the major organic product(s) in the reaction below. Answer: Section: 6-7 Which of the following alkenes yield(s) 3-bromo-3-methylpentane as the major product upon addition of HBr? I and II only III only I, II, and III only all of them none of them Answer: D Section: 6-7 Which of the following carbocations is likely to rearrange? I II III IV II and IV Answer: E Section: 6-7 42) What is the name of the major organic product of the following reaction? 3,3-dimethyl-1-butanol 3,3-dimethyl-2-butanol 2,3-dimethyl-2-butanol 2,3-dimethyl-1-butanol 4-methyl-2-pentanol Answer: C Section: 6-7 43) Provide the major organic product(s) in the reaction below. Answer: Section: 6-10 44) Give the major organic product of the reaction shown. A) B) C) D) E) Answer: C Section: 6-7 45) Provide the major organic product(s) in the reaction below. Answer: Section: 6-6 Which statement is true in the hydroboration-oxidation of an alkene? Markovnikov orientation and syn addition occur. Markovnikov orientation and anti addition occur. Anti-Markovnikov orientation and syn addition occur. Anti-Markovnikov orientation and anti addition occur. Markovnikov orientation and both syn and anti addition occur. Answer: C Section: 6-8 47) Provide the major organic product in the reaction below. A) B) C) D) E) Answer: A Section: 6-8 48) What reagents are needed to accomplish the following transformation? H2O/H+ H2O/Peroxide OH- BH3 E) 1. BH3/ 2. HO-, H2O2, H2O Answer: E Section: 6-8 Draw the major organic product generated in the reaction below. Answer: Section: 6-8 Draw the major organic product generated in the reaction below. Answer: Section: 6-8 51) Provide the major organic product(s) in the reaction below. Answer: Section: 6-8 Provide the structure of the major organic product in the reaction below. Answer: Section: 6-8 53) What is the major product of the following reaction? I II III IV V Answer: B Section: 6-9 54) Which reaction intermediate is formed when Br2/CCl4 reacts with cyclohexene? 31523898795000 I II III IV V Answer: D Section: 6-9 9613902203450055) Draw the major organic product generated in the reaction below. Answer: Section: 6-9 56) Draw the major organic product generated in the reaction below. Answer: Section: 6-9 Complete the following reaction and provide a detailed, step-by-step mechanism for the process. 9194808763000 Answer: (plus enantiomer) Section: 6-9 Provide a detailed, step-by-step mechanism for the reaction shown below. Answer: Section: 6-9 59) Draw the structure of the major product of the reaction below. Answer: Section: 6-9 Provide the major organic product(s) in the reaction below. Answer: Section: 6-9 94043522288500Provide the major organic product(s) in the reaction below. Answer: Section: 6-19 Give the product for the reaction that occurs when 1-pentene is treated with Cl2. 1-chloropentane 2-chloropentane 1,1-dichloropentane 2,2-dichloropentane 1,2-dichloropentane Answer: E Section: 6-9 Give the intermediate for the halohydrin reaction. a halonium ion the most stable carbocation with OH on the adjacent carbon the most stable carbocation with X on the adjacent carbon a cyclic oxonium ion the most stable carbanion Answer: A Section: 6-9 Provide the major organic product in the reaction below. A) B) C) D) E) Answer: A Section: 6-9 92964025781000Provide the structure of the major organic product in the reaction below. Answer: Section: 6-9 Draw the product. Answer: Section: 6-9 Provide the structure of the major organic product in the reaction below. Answer: Section: 6-9 Draw the products. Answer: Section: 6-10 Provide the structure of the major organic product in the reaction below. Answer: Section: 6-10 Which of the following reagents gives the reaction shown below? CH3CH= CH2 + ? ? CH3CH2CH3 H2/HCl H2/H2SO4 H2/Ni H2O/Ni H2O/H2SO4 Answer: C Section: 5-9 Provide the major organic product(s) in the reaction below. Answer: Section: 5-9 What is the product of the hydrogenation of an alkene? dihaloalkane alkane haloalkane alcohol ether Answer: B Section: 5-9 Provide the structure of the major organic product in the reaction below. Answer: Section: 5-9 96139043434000Which of the following is the most stable alkene? A) B) 96139022796500C) D) 96139024003000E) Answer: E Section: 5-9 Upon hydrogenation, which of the following alkenes releases the least heat per mole? 3,4-dimethyl-1-hexene (Z)-3,4-dimethyl-2-hexene (E)-3,4-dimethyl-2-hexene (Z)-3,4-dimethyl-3-hexene (E)-3,4-dimethyl-3-hexene Answer: E Section: 5-9 Which of the following alkenes would have the smaller heat of hydrogenation? Explain. CH2CH2 or CH2 Answer: CH2 would have the smaller heat of hydrogenation because the double bond is more stable than that of CH2. The greater stability is due to the fact that the double bond in propene is more alkyl substituted than that of ethene. Section: 5-9 What configurations are found in the product(s) of the reaction below? 1R,2R only 1S,2S only 1R,2S only an equal mixture of 1R,2R and 1S,2S an equal mixture of 1R,2R and 1R,2S Answer: D Section: 6-13 Provide the structure of the major organic product of each of the following reactions. Answer: Section: 6-16 Identify the products of cis-3-methyl-3-hexene with hydrogen bromide. (2R, 3S)-3-bromo-3-methylhexane (2R, 3R)-3-bromo-3-methylhexane (2S, 3R)-3-bromo-3-methylhexane (2S, 3S)-3-bromo-3-methylhexane all of the above answers Answer: E Section: 6-13 Give the types of products formed from the bromination and catalytic hydrogenation (using D2) of cyclohexene. Answer: Threo or trans isomers from bromination; Erythro or cis isomers from hydrogenation. Section: 6-13 Complete the following tree of reactions by giving the major products: 94551525781000Answer: Section: 6-13 The product of this reaction is called a(n) peroxide. peroxy. epoxy. epoxide. oxide. Answer: D Section: 6-10 Predict the product of the following reaction. 96139086995 Answer: Section: 6-11 1005839219749Predict the product of the following reaction. Answer: Section: 6-11 914400394995In the following ozonolysis reaction, if we start with optically pure S-enantiomer, the product obtained will be racemic mixture. unequal mixture of R and S enantiomers. diastereomers. meso compounds. optically pure S-enantiomer. Answer: E Section: 6-11 How many distinct products will be obtained in the ozonolysis of the following compound? 4864908126016001 2 3 4 5 Answer: A Section: 6-11 A reaction in which a mixture of two constitutional isomers is obtained but one is formed in higher amounts than the other is called a regioselective reaction. regiospecific reaction. stereospecific reaction. stereoselective reaction. successful reaction. Answer: A Section: 6-4 96139022225000Hydrogenation of the following compound generates constitutional isomers. identical compounds. enantiomers. diastereomers. meso compounds. Answer: D Section: 6-13 Hydrogenation of which of the following would generate an optically active product? I II III IV V Answer: A Section: 6-13 Show all the stereoisomeric products of the following reaction. 960119259103Answer: Section: 6-13