Exam_1_White_Key - was 44.7(12 total points CEM251/Fall...

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Unformatted text preview: was 44.7 (12 total points) CEM251/Fall 2010/First Exam ..... (page 1) 1. Draw the structure of each of the following molecules: 2 pts. 8) 2,2,3-trimethylpentane 2 pts. b) cis-l-t— butyl-4-chloro'cyclohexane (use wedge-dotted lines to show stereochemistry) 2. Give the lUPAC name for each of the following molecules: b) Br CH3 ' l I CH30H2 CH‘_CHCH3 3. Give the formal charge on the indicated atoms in the following structure: zptS'Ew :'ol': ff- 2pts. C\ CH3/ \N: CH3 CEM251/Fall 2010/First Exam ..... (page 2) (12 total points) 4) Molecule X has 20 carbons, three 31: bonds and 2 pts. one ring. How many hydrogens does X have? 3 Ar NCHZCH3 l? CHZCEC—C—OH Y For the above molecule Y: a) The number of Sp3 carbons in Y is? 2 pts' b) The number of Sp2 carbons in Y is? -2 pts' C) The number of Sp carbons in Y is? -2 pts. d) The number of :1: 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? s.— 2 pts. Answer CEM251/Fall 2010/First Exam ..... (page 3) (6 total points) 7. Draw a Newman projection of a staggered conformation of 2-bromo-2-methylpentane, viewed down the 02—03 bond. Answer 8. Draw a wedge-dotted line structure for molecule X. Br H 2 pts. H I CH3 H/ \Br CH3 Br X Answer 9. Draw a wedge-dotted line structure for molecule Y. 2 pts. Br CH3 H H Br H H CH3 Y Answer CEM251/Fall 2010/First Exam ..... (page 4) (8total 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. 11. Indicate the isomeric relationship (constitutional, configurational or conformational) of the following molecules: a) CH3 ~H H CH3 CH3 ' GL 2 pts. Hm->—< and HWHWH {1m ? o rm o in ass—M H CHs H H Answer ’ Cl Cl b) H and QDNfismmi-imfl. ”‘3- H H . Cl Answer OH OH CH3 and ""'CH3 2 pts. Answer CEM251/Fall 2010/First Exam ..... (page 5) (8 total points) 12. a) How many asymmetric carbons are present in the structure of A, below? CH3 CH3 0 2 ms- CH3 Answer A b) How many configurations are possible for 2 pts. molecules with the constitution of A, above? Answer 0) How many configurations are possible for molecules with the constitution of B, below? 9. it 2 pts. CH3C—CH—CH—CCH3 l l 5 OH OH Answer B 13. Which one of the following molecules (X, Y or 2) has a plane of symmetry (a 0 plane)? OH OH OH ““‘CH3 2 pts- Answer ""'CH3 x H3 CEM251/Fall 2010/First Exam ..... (page 6) (14 total points) 14. Label (in the boxes) the acids and the bases in the following acid-base reaction: 0 O 0 II (+) o’H (-) ll HOSOH n + O—fi—OH CH3C— OH —-‘ CHSC\QH O u m - fl 2 pts. 2 ms 2 pls 2 pts. 15. (2 pts.) Given that nitro groups (-N02) are electron-withdrawing substituents, encircle the side favored at equilibrium in the following acid-base reaction: c02H co2() 16. E0 A _ ——b progress Of reaction a) For the above energy diagram, which product A 2 9‘3- (A, B or C) is formed fastest? C _ _ 2 pts. b) Which product (A, B or C) is most stable? CEM251/Fall 2010/First Exam ..... (page 7) (18 total points) Cl CI Ci Cl QC H3 G‘N‘CHa QCHS Q“‘“CH3 A B C 1'- D [F235 [mall \‘54'3-9 18. For the above four structures (A, B, C and D)- , 2 pts. a) Which one is (1 R, 28H—chloro-2-methylcyclopentane? trans-1 chloro 2-methylcyclopentane? “.CH 0) Which one is identical to X? Q; 3 2 pts. X Cl lSJZE. d) - 2 pts. Which one would be mixed with C to form a racemic mixture? 13) Which two may be present in a bottle labeled E2 pts- 2 pts. e) Which one has the same melting point as A? E 2 pts- 2 pts. f) Which two are diastereomers of D? E) + g) If B has a specific rotation of ( )10° which 2 pts. one must have a specific rotation of(- )100? CEM251/Fall 2010/First Exam ..... (page 8) (22 total points) CH5 CH3 CH3 CH3 Br H H I Br Br H H Br | I I CH3 CH3 CH3 CH3 A B C D afllgg 2&3'2‘5 aR,3S 23,35 19. For the four structures above (A, B, C and D): . . . 2 pts. a) Which one Is (28, 3S)-2,3—d|bromobutane? b) Which two are identical and represent the (5 2 pt: C. 2 pts' meso form of 2,3-dibromobutane? CH .Br C) Which one is identical to Z? 3 H A 2 pts' Br"‘H H 1‘ {CH3 R Z 2 pts. d) Which one is the enantiomer of A? e) Which two have no plane of symmetry in any conformation? 2 pts' . . . 2 MS 2 pts. 1‘) Which two are optically active PT + 3 compounds? 2 pts- 9) Which two are chiral molecules? ...
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