Exam_1_Green_Key-1 - 695 CEM251/Fall 2010/First Exam(page...

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Unformatted text preview: 695% CEM251/Fall 2010/First Exam.....(page 1) (12 total points) 1. Draw the structure of each of the following molecules: 2 pts. 8) 2,3,3—trimethylpentane 2 pts. b) trans—1-bromo-4-isopropy|cyclohexane (use wedge-dotted lines to show stereochemistry) 2. Give the lUPAC name for each of the following molecules: a ) ii 3" . =. {I _t . :3 Mi L 2.. " hi?! 1 tori"... 1. C: E‘ 'L , ,.-_ '- " '. 'i_ ' .Xflh‘lJ‘ 8- CH3 b) ' | » CH30H(I3HCH20H3 CI 2pts. 4 . A-‘o’H tin/‘2‘“ CH/ \-O- CEM251/Fall 2010/First Exam.....(page 2) (12 total points) 4) Molecule X has 22 carbons, three Tl? bonds and 2 pts. one ring. How many hydrogens does X have? {3) <8 5) o fir Y For the above molecule Y: 2 pts. a) The number of Sp3 carbons in Y is? 2 t . b) The number of Sp2 carbons in Y is? p S C) The number of Sp carbons in Y is? 2 pts. d) The number of It bonds in Y is? 2 pts. 6) How many of the six methyl groups in molecule A will occupy an equatorial position in A’s more stable chair conformation? CH3 CH3 \ a," 6“ 2 pts. CH3 Answer CEM251/Fall 2010/First Exam.....(page 3) (6Vtotal points) 7. Draw a Newman projection of a staggered conformation of 2-chioro-2-methyibutane, viewed down the C2-C3 bond. 2 pts. CH3 H 2 pts. Br CH3 Answer 9. Draw a wedge-dotted line structure for molecule Y. 2 pts. H CH3 Br H H CH3 Br Answer CEM251/Fall 2010/First Exam.....(page 4) (8 total points) 10. Based on chair-form stability, draw a wedge-dotted line structure of the most stable configuration of 1,3,5-trimethylcyclohexane: 2 pts. Answer 11. Indicate the isomeric relationship (constitutional, configurational or conformational) of the following molecules: OH OH a) . ! ‘ 1 ‘l 2 and o C D l"; “L LL ‘1". Ct 15-146- . CH3 Answer H b) CH3 :5 H 2pts. Hn|"“‘ H CH3 Answer Br 0) H and Br CEM251/Fall 2010/First Exam.....(page 5) (8,total points) 12. a) How many asymmetric carbons are present in the structure of A, below? 2 pts. Answer CH 3 CH3 CH3 CH3 0 A b) How many configurations are possible for 2 pts. 3’4 molecules with the constitution of A, above? I (0 cm Answer c) How many configurations are possible for molecules with the constitution of B, below? 0 fl ll HO—C—CH—CH—C—OH v 2 pts' | l ‘4 Br Br Answer B 13. Which one of the following molecules (X, Y or 2) has a plane of symmetry (a 0 plane)? Br Br Br CH3 l .w 2 pts. CH3 Answer CH3 Y Z CEM251/Fall 2010/First Exam.....(page 6) (14 total points) 14. 15. 16. Label (in the boxes) the acids and the bases in the following acid-base reaction: o 0 II II CI—S—OH CHE—OH c'S + o 2 2 DIS. (2 pts.) Given that nitro groups (-NOQ) are electron-withdrawing substituents, encircle the side favored at equilibrium in the following acid-base reaction: EFF—fl — COZH _.— '-—. /' 0020) K© + \ No2 002H f ll| _/ J: g“ I COQH # (01+ No2 Eo progress of reaction a) For the above energy diagram, which product (A, B or. C) is formed fastest? 2 pts. 2 pts. E b) Which product (A, B or C) is most stable? CEM251/Fall 2010/First Exam.....(page 7) (1 8 total points) 18. For the above four structures (A, B, C and D): 2 pts. 8) Which one is (1 R, 2S)—1—chloro-2-methylcyclopentane? b) Which two may be present in a bottle labeled E) 2 pt: 2 pts- trans-1—chloro-2—methylcyclopentane? . “\CH c) Which one is identical to X? 3 2 MS- X Cl 1=‘--_ 3 _ I . ' I 2 pts. d) Which one would be mixed with C to form a racemic A mixture? 2 pts. 9) Which one has the same melting point as A? 2 lots 2 pts. f) Which two are diastereomers of D? A + 9) if B has a specific rotation of (+)10°, which 2 pts' one must have a specific rotation of (-)10°? CEM251/Fall 2010/First Exam.....(page 8) (22 total points) 19. For the four structures above (A, B, C and D): CH3 CH3 CH3 CH3 Br /H H /Br Br\ /H H /Br H I Br H Br Br I H Br I H CH3 ' H3 CH3 CH3 A B c D 2 i: .5 2 5n» :7; til :-.i K i" . . . 2 pts. a) Which one is (28, 3S)-2,3-dibromobutane? b) Which two are identical and represent the 2 t: 2‘ 2 pts- meso form of 2,3-dibromobutane? A _l.. . . . _ CH .Br _ C) Which one is Identical to Z? 3 H l 2 ptS' Br""'>‘ .11. < LI H ‘ t 9H3 3 L" . '0 J ~ 2 2 pts. d) Which one is the enantiomer of B? M... 9) Which two have no plane of (“I 2 pt: 1 2 PtS- symmetry in any conformation? F— H" . . 2 ts. _ 1‘) Which two are optically active 6 p + 1 2 pts compounds? " K, . V __ 2 ptS- I 2 pts. 9) Which two are chiral molecules? it + 1"“ ...
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This note was uploaded on 12/09/2010 for the course CEM 251 taught by Professor Rathke during the Fall '07 term at Michigan State University.

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Exam_1_Green_Key-1 - 695 CEM251/Fall 2010/First Exam(page...

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