F06 midterm2 key

F06 midterm2 key - Aw w Midterm -2- Fall 2006 Chem-30 A...

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Unformatted text preview: Aw w Midterm -2- Fall 2006 Chem-30 A Last First Name Name Studmt ID Number : Name of yom‘ TA: Breeyawn / Paul / Ryan Manashi Chattajee Ph.D. Chem 30 A Fall 2006 Midterm # 2 (50 mins) Monday November 20, 2006 fiflflflflflfl 1.2 1.5 1.8 2.1 2.5 3.0 flfiflflflflfl 1.0 1.6 1.8 2.0 2.4 2.8 gamma-a 1.7 2.1 2.5 Blectronegafivity values for some atoms (Pauling scale) DO NOT OPEN THIS EXAM UNTIL INSTRUCTED TO DO SO Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-30 A 1. For each pair of structures given below, circle the most stable structure. If you believe the two structures are identical in energy, circle both. In the box, provide a brief (6 words or fewer) explanation for your choice. No credit for incorrect or incomplete explanation. (12 points) \p* 2. Rank the following compounds in the order of increasing acidity. (3 POINTS) Cl Cl CIWSH SH OH A B C Manashi Chatterjee Ph.D. Midterm -2- Fa112006 Chem-30 A 3. Give the major product/products formed in each of the following reaction (including stereochemistry where appropriate) in the large box. If more than one isomer is formed write both and indicate ratio. For two step reactions just give only the final product. DO NOT DRAW INTERMEDIATES. (4 POINTS each) Hg(0Ac)2, H20 —> NaBH4 H20 H2 S 04 i) OsO4 —————-> ii) NaHSOg, H20 Molecule has chiréfl Cenk’i’s ap‘cs ‘6? Oak, me, hqditxfim. Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-30 A 4. Prostaglandins, such as PGEl are potent hormones that control a wide variety of physiological functions in humans. Answer the following questions after carefully analyzing the structure of PGE1 (21 POINTS) Prostaglandin E1 (PGEI) Cdnd 99MB) q 3 P30 a) The index of hydrogen deficiency of PGE1 is 3gb b) Name and Circle all the functional groups present in PGEl (in the structure above). \ a. \ c) PGE1 contains a 5 membered ring which is normally called We, ‘17. Cork) 1 n n o e a *3 4*; d) PGEI contains ch1ra1 carbons. (Indicate each ch1ra1 center With a * on the 5 structure . e) The total number of possible stereoisomers that can exist are i f) The double bond in PGEl is m (Cis / Trans) \ g) PGE1 has & number of 3° carbons in its structure. a h) At physiological pH PGE; will exist in which form (Neutral, Cationic or Anionic)? Answer isrfimcm C a i) The form present at physiological pH is more soluble in water. (True or false) Answer is: T! n6 j) Transform the molecule below to synthesize a new derivative of PGE1 that is more a, acidic than the parent PGEI. (USE a suitable atom fiom periodic table that will be appropriate; Use only one or two new atoms to transform the molecule below) a\p’t‘j Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-30 A 5. For each of the structures given below, identify the relationship between the structures as drawn as either identical, stereoisomers, conformational isomers or constitutional isomers. Then, for each pair of structures, circle the most stable structure. If you believe that the two structures are identical, then circle both the structures. /c/,_M --—~~—\.\ (10 POINTS) H3 K a) ‘ ' \‘derxiu‘cxfl that mi Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-3O A 6. a) Circle the location of the isoprene units in the terpene shown below. How many isoprene units make up Cedrene? . (6 POINTS) Answer is: b) How many asymmetric carbons . - - esent in Cedrene? Indicate by * the chirality centers in the above terpene. Answer is: i a 7. What is the best choice of reagent to perform the following transformation? ‘ S . (2 POINTS) 0 “m3 ‘ Q‘s ? . Br —-——-—-> \ _ 1. Brz, H20 2. Brz, CH2C12 3. N-bromosuccinimide 4. HBr, CH2C12 Answer is: l 8. What type of reactive intermediate is formed in the reaction of an alkene with HBr to give a bromoalkane? (l POINT) a) cyclic bromonium ion b) carbanion c) radical d) carbocation Answer is: d \ 9. Which of the following explains the observation that the tert-butyl carbocation is more stable than the 1-butyl carbocation? ‘(1 POINT) a) hyperconjugation b) conjugation c) hybridization d) electronegativity Answer is: A Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-30 A 10. What is the correct order of stability of the following carbocations (more stable >; less stable)? (2 POINTS) (9 G) - (B 1 2 3 a)1>;2>;3 b)3>;l>;2 c)l>;3>;2 d)2>;3>;l Answer is: g l 11. What type of reactive intermediate is formed in the reaction of an alkene with Br; and H20 to give a bromohydrin? (2 POINTS) a) radical b) cyclic bromonium ion c) carbanion d) carbocation Answer is: \D 1&3 12. What is the major organic product obtained from the following reaction? (2 POINTS) 13. Which of the following carbocation rearrangements is feasible (exothermic)? (2 POINTS) Manashi Chatterjee Ph.D. Midterm -2- Fall 2006 Chem-30 A 14. What is the step Wise mechanism of the reaction shown below? Show all intermediates with all appropriate lone pairs, formal charges and curly arrows to show the formation of the product. Keep your work neat and clean and in steps. (10 POINTS) Use this box if you need more space Manashi Chatteijee Ph.D. Midterm -2- Fall 2006 Chem-30 A 15. a) Rank the following compounds in the order of decreasing acidity. (5 POINTS) 0 O O O H /U\ /“\/u\ ©/ CHBCOOH A B C D Answeris:D_> > E) > A b) Circle the most acidic proton in each of the molecules shown below. \(oJr 16. Draw curved arrow and complete the following reaction. Identify the acid and bases in the reactions. (5 POINTS) ...
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F06 midterm2 key - Aw w Midterm -2- Fall 2006 Chem-30 A...

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