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Unformatted text preview: Chemistry 140A
Fall Quarter, 2005
Final Exam, Friday December 9 first name middle
initial last name Student ID Number
10 score Regrade Quest
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
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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:
(b) 109.5˚ (c) 180˚
(e) 360˚ 5. The energy difference between axial and equatorial methylcyclohexane is (in
(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
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
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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