Set 3 with Exams

Set 3 with Exams - Chem 210 Training Set III Organic...

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Chem 210 Training Set III Page 1 of 16 Organic Chemistry: Chem 210 Training Set III The questions are arranged approximately in the order of the coverage of material in the lecture. This set covers the material of the third exam. Notes: I. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. II. The stereochemistry conventions are illustrated below: Br OH Br OH Br Br OH OH No stereochemistry shown Absolute stereochemistry shown Relative stereochemistry shown Absolute stereochemistry on one center, unspecified stereochemistry on the other III. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H 3 CCOO), MCPBA = m- chloroperbenzoic acid. 1 . In the polar reaction of vinyl chloride with HBr the only product formed is 1,1- bromochloroethane ( not 1-bromo-2-chloroethane): ClCH=CH 2 + HBr ClBrCHCH 3 (not: ClCH 2 CH 2 Br) What is the best explanation for this preference? a) The electrophile prefers to add to the chlorine-substituted carbon. b) Chlorine is causing steric hindrance for the addition of the bromine. c) The bromine electrophile is attracted to the lone electron pairs on chlorine. d) The two possible carbocations formed have the same stabilities, but 1,1- bromochloroethane is much more stable than 1-bromo-2-chloroethane. e) The carbocation formed by protonation on the unsubstituted carbon is stabilized by resonance. f) A bromonium ion prevents attack on the carbon bearing the chlorine.
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Chem 210 Training Set III Page 2 of 16 2 . The molecule of I-N 3 adds to alkenes by an electrophilic mechanism similar to that of Br 2 . Taking into account the relative electronegativity of I (2.5) and N (3.0), and the fact that N 3 is a stable anion, what is the most likely product of the following reaction? 3 . Which of the compounds listed is the product of the following reaction? 4 . Which of the following is not a redox reaction? CH 3 I-N 3 I N 3 H CH 3 N 3 I H CH 3 H N 3 I CH 3 H I N 3 CH 3 a) ? b) c) d) e) f) N 3 H I CH 3 I H N 3 CH 3
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Chem 210 Training Set III Page 3 of 16 5 . When 4-penten-1-ol is treated with aqueous bromine, a cyclic bromo-substituted ether is formed rather than the expected bromohydrin. Select the explanation that best accounts for this result. a) The ether is the result of a hydride shift in the initially formed carbocation. b) The ether is formed in the intramolecular nucleophilic attack on the initially formed bromonium ion. c) The reaction is initiated by the protonation of the π system by the –OH group. d) The ether is formed by a nucleophilic attack of the π bond on the –OH group. e) The initially formed bromonium ion undergoes an alkyl shift to form new C-O bond.
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This note was uploaded on 04/04/2008 for the course CHEM 210 taught by Professor Several during the Spring '08 term at Rutgers.

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Set 3 with Exams - Chem 210 Training Set III Organic...

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