FALL05 Final

FALL05 Final - Chemistry 140A Whitesell Fall Quarter, 2005...

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Unformatted text preview: Chemistry 140A Whitesell Fall Quarter, 2005 Final Exam, Friday December 9 first name middle initial last name Student ID Number Regrade Quest 1 2 3 4 5 6 7 8 9 10 Points 15 12 10 5 5 10 12 15 15 10 score Regrade Quest 11 12 13 14 15 16 Points 12 10 13 28 15 13 Points score 200 Your answers to this exam are to be only your own work. You may use no written information during this test period other than the eight pages of this exam. You may not use the back of any pages for answers. Up to one week after your exam is returned you may submit it for regrading if and only if you have made NO marks on the exam except for a star (*) next to the number(s) above of the question(s) you would like regraded. your signature (read the above before signing) To request regrading, sign below and check the appropriate boxes. your signature I would like the questions marked with a star (*) regraded (check box at right) If you feel that we have made an addition error in your score, check the box at the right 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1. Write out the propagation steps of the mechanism for the free radical chlorination of ethane (CH3CH3). Use the appropriate curved arrows to show the movement of electrons. 2. Draw both chair conformations for each of the following dimethylcyclohexanes. Use the provided chair representations. 3, Provide Newman Projections for guache and anti butane. Anti Gauche Your signature (in ink)______________________________________________ 2 4. The C—C—C bond angle in cyclopropane is approximately: (a) 60˚ (b) 109.5˚ (c) 180˚ (d) 90˚ (e) 360˚ 5. The energy difference between axial and equatorial methylcyclohexane is (in kcal/mole): (a) 1.35 (b) 0.9 (c) 1.7 (d) 2.7 (e) 25 6. Assign the absolute stereochemistry (R or S) to all stereocenters in the following molecules (not all molecules have stereocenters). Indicate which are meso isomers. Do not guess as 1 point will be subtracted for each wrong answer. H OH H H OH H H OH 7. Provide oxidation levels (states) for the atoms to which the arrows are pointing (put your answers inside the appropriate circles), O OH OH Your signature (in ink)______________________________________________ 3 8. Write out a detailed mechanism for the reaction shown below. Use curved arrows to account for all bond breaking and bond making steps. O Br HBr 9. Write out the mechanism for the reaction shown below. Use curved arrows to account for all bond breaking and bond making steps. Br H2O OH Your signature (in ink)______________________________________________ 4 10. Reaction of the bromide at the right, below, with water in a solvolysis reaction gives two alcohols. Give structures for the two products and explain clearly how they are formed (pictures here are worth LOTS of words). Br CH3 CH3 11. Write two different ether syntheses for 1-ethoxybutane (CH3CH2OCH2 CH2CH2CH3). Your signature (in ink)______________________________________________ 5 12. Formulate the product(s) of each of the follow steps. Is a mixture of stereoisomers possible in either step? If so, show both possible isomers. OH Na2Cr2O 7 NaBH4 H2S O4, H2O EtOH C H3 13. Write a synthetic scheme for the conversion of 2-propanol (CH3)2CHOH, into 2-methyl-1-chloropropane, (CH3)2CHCH2Br. You may use anything else that you need so long as the three carbons of 2-propanol are incorporated into 2-methyl-1chloropropane. Show all reagents (but solvents are NOT required). OH Cl several steps Your signature (in ink)______________________________________________ 6 14. Provide the expected major organic product from each of the following reactions: O NaBH4 A. EtOH O C H3Li B. H2O OH Na2Cr2O 7 C. H2S O4, H2O OH D. Na2Cr2O 7 H2S O4, H2O Br E. O Br H2O F. G. Br NaOH Your signature (in ink)______________________________________________ 7 15. For each of the reactions shown below, check the appropriate box indicating the correct mechanistic pathway followed in converting starting material to product. Br E1 E2 Br E1 OH H2O E2 SN1 SN2 NaOH SN1 OH SN2 Br KOC(CH3)3 E1 E2 SN1 SN2 16. Draw a representation of the transition state for the following reaction. C H3Br + OH C H3OH + Your signature (in ink)______________________________________________ Br 8 ...
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