Chemistry 261 Homework 3: Chapters 5, 6 Out: 11/20/17 Due: 11/30/17 Point Value: 9 points (7 EC points possible when combined with part I)

Transcription

1 Chemistry 261 omework 3: Chapters 5, 6 ut: 11/20/17 Due: 11/30/17 Point Value: 9 points (7 EC points possible when combined with part I) The following homework assignment contains 28 questions valued at 1/3 point/question Name: 1. Concerning the relative stabilities of alkenes, which is a false statement? Unless hydrogenation of the alkenes gives the same alkane, heats of hydrogenation cannot be used to measure their relative stabilities In general, the greater number of alkyl groups attached to the carbon atoms of the double bond, the greater the stability of the alkene The greater the quantity of heat liberated on combustion or hydrogenation of a series of isomeric alkenes, the greater the energy content of a given double bond d. trans-cycloalkenes are always more stable than cis-cycloalkenes e. N/A; all are true statements 2. Neopentyl alcohol cannot be dehydrated to an alkene without undergoing rearrangement. What is the principal product formed in the dehydration of neopentyl alcohol? I II III I II III d. IV e. V IV V

2 3. What is the major product for the following reaction? Et, heat Et d. e. 4. The interaction of the alkene bond with an electrophile results in the formation of a species termed a complex. Which of the following cannot form a complex with an alkene? + N 3 Ag + d. g +2 e. BF 3

3 5. (R)-3-chloro-1-butene reacts with by Markovnikov addition, followed by separation of the products by gas chromatography 1. ow many fractions would be obtained and how many would be optically active? 1 fraction, optically active 2 fractions, 1 optically active 2 fractions, both optically active d. 3 fractions, 1 optically active e. 3 fractions, 2 optically active 6. What is/are the likely product(s) of the following reaction? d. (a) & (c) e. None of the above 1 Gas chromatography is a chromatographic technique that typically uses a temperature stable organic compound linked to the inside of a glass tube as a stationary phase, and an inert gas as the carrier phase. The glass tube, often 50 m in length and coiled, is placed in an oven. As the oven is heated, successive components are volatilized and carried through the column to a detector, partitioning as they travel

4 7. What is/are the principal product(s) of the following reaction? 2, C 4? C 3 C 3 C 3 C 3 C 3 7 C 3 7 C 3 7 C 3 7 I II III IV Equal amounts of I & II Equal amounts of II & III Equal amounts of III & IV d. I & II as major products, III & IV as minor products e. All of the above in equal amounts 8. What is the major product of the following reaction sequence? 2 1. I 2. t-buk, t-bu d. e. More than one of the above 2 Recall tbuk acts as a hindered base, giving the anti-zaitsev product

5 9. What is the major product of the following reaction? g(ac) 2, 2 NaB 4, Na d. e. 10. What is the major product of the following reaction? B 3 :TF 2 2, Na d. e. More than one of the above

6 11. What is the major product of the following reaction series? , Pd/CaC 3, quinoline 2 B 3 :TF 2 2 2, Na d. e. 12. Which of the following is a possible structure for an alkene of formula C 9 14 that adds 1 mole of hydrogen on catalytic hydrogenation and which gives the diacid shown upon treatment with hot, basic KMn 4? I II III I II III d. IV e. V IV V 3 2 on Pd/CaC3 in the presence of quinolone is known as Lindlar s catalyst, and converts alkynes to alkenes (specifically cis alkenes)

7 13. What is the major product of the following reaction sequence? 1. Et, 70 o C 2 3, C 2 2, -78 o C 2 Me 2 S d. C C e. None of the above 14. ow many stereogenic centers are there in the cholesterol lowering drug lovastatin (Mevacor ) d. 7 e. 8 (Lovastatin)

8 15. What is the molecular formula of the alkane 4 of smallest molecular weight which possesses a stereogenic center? C 4 10 C 5 12 C 6 14 d. C 7 16 e. C Which of the following are chiral? 3 C C 3 C 2 5 I C 3 C 3 C 2 5 II 3 C C 2 5 III C 2 5 C 2 I & II 3 C IV C 2 5 V III & IV I, II, III, & IV d. IV e. All of the above 17. What is the total number of compounds, stereoisomers included, which fall under the name dichlorocyclopentane? d. 7 e. 8 4 Cycloalkanes excluded, as may be deduced from the formulas given

9 18. ow many stereogenic centers are found in the molecule adamantane? d. 3 e The pair of compounds shown below would have C 3 F C 2 C 3 C 2 C 3 C 3 F I II the same melting point different boiling points equal but opposite optical rotations d. more than one of the above e. all of the above 20. Compounds I & II are D 3 CS D SC 3 I II Constitutional isomers Enantiomers Identical d. Diastereomers e. Not isomeric

10 21. The 2 compounds shown are and Identical Enantiomers Diastereomers d. Conformational isomers e. Meso forms 22. The 2 compounds shown are C 3 C 3 F F 2 N C 3 3 C F F N 2 Constitutional isomers Enantiomers Diastereomers d. Identical e. None of the above applies 23. Compounds I and II are I II Constitutional isomers Enantiomers Diastereomers d. Identical e. None of the above applies

11 24. The Cahn-Ingold-Prelog stereochemical designations for the isomer of 1,1,2,4- tetrachlorocyclopentane shown are 2R,4S 2S,4R 2R,4R d. 2S,4S e. The R,S designation does not apply here 25. (2R,4S)-2,4-dichloropentane and (2S,4R)-2,4-dichloropentane are enantiomers diastereomers identical d. conformational isomers e. constitutional isomers 26. Please draw the bond-line structure corresponding to (2S,3S)-2,3-dihydroxybutanedioic acid 27. ow many stereoisomers correspond to 2,3-dihydroxy-2,3-butanedioic acid? d. 4 e. 5

12 28. Pure L-phenylalanine has a specific rotation of o. What is the enantiomeric excess of a 10.0 g/ml solution of phenylalanine which when placed in a standard 1.00 dm cell and analyzed in a polarimeter rotates plane polarized light o? Enantiomeric excess: