230-001 2003 Organic Exam 4-A page - 1 -Cumulative Part (100 pts) 1. (10 pts) Draw a line structure diagram for acetate: CH3CO2(-). Your structure must include all lone pairs and formal charges. C and H atoms may be shown either implicitly or explicitly for full credit. 2. (10 pts) Draw the structure of (Z)-1-chloro-2-pentene. 3. (10 pts) Draw the best structure of the E2 product of (1R, 2S)-1-bromo-2-methylcyclohexane and tBuOK. 4. (10 pts) Circle the chiral molecules; draw an X over the achiral molecules. trans-1,2-dimethylcyclopentanetrans-cycloocteneC2,3-pentadieneOOOOOO2,3,11,12-tetramethy-18-crown-6HHtrans-decalinstructures for 4. 5. (10 pts) How many possible stereoisomers (enantiomers + diastereomers) does 4-methyl-3,5-heptanediol have? _________ How many possible stereoisomers (enantiomers + diastereomers) does 2-methyl-3,4-pentanediol have? _________ Answer for 1: Answer for 2: Answer for 3:230-001 2003 Organic Exam 4-A page - 2 -6. (10 pts) OHHH Upon treatment with H3O(+) the bicyclic carbon framework at left rearranges to make a bicyclic alcohol. Please draw the structure. 7. (10 pts) CNDraw the high-energy conformation of this molecule. 8. (10 pts) Draw the SN1 products of this optically pure starting material. BrCH3CH2OHproblem 8 9. (10 pts) Draw a Newman projection of the most stable conformation of (S)-2-chlorobutane. Put the carbon attached to the chlorine in front and sight down the bond between C2 and C3. Hint: the lowest energy conformation of 1-chloro-1-methyl-cyclohexane puts Cl in an axial position. 10. (10 pts) How many 13C signals are there in the following molecules? 2 pts. ____ 2 pts. ____ 3 pts. ____ 3 pts. ____ Answer for 6: Answer for 7: Answer for 9:230-001 2003 Organic Exam 4-A page - 3 - 11. (10 pts) Predict the product. hvsolventNOOBr+11. 12. (10 pts) Predict the Diels-Alder product. Stereochemistry is very important! +NOOHheatsolvent12 13. (9 pts) Draw three lowest-energy molecular orbitals of cyclopentadienyl anion. Label these X1-X3 with one being the lowest-energy orbital. Hint, two of them have the same energy, in lecture we counted bonding, antibonding and non-bonding components in molecular orbitals. You may look at the pi-system from above and draw the atomic p orbitals as circles. (5 pts) Are all of three of these MO’s occupied? ________ (6pts) How many more pi-molecular orbitals are there? ________ Orbitals for 13.230-001 2003 Organic Exam 4-A page - 4 -14. (10 pts) Draw a circle around the aromatic (unusually stable) molecules. Put an X through the unstable molecules. NBBNBNBNNB 15. (10 pts) Think about the transition states of these two reactions. One readily happens the other does not. Explain why one occurs and the other does not in terms of aromaticity? For the brevity refer to the reactions as 15a and 15b. CNO+CONCNO+OCN15a15b _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ 16. (5 pts) a. Complete the reaction energy diagram by using it to describe a reaction that has one intermediate. (6 pts) b. Use the ‡ sign to label the transition state(s). c. (4 pts) Would you expect that the reaction vessel gets warmer, colder or maintains the same temperature as the reaction occurs? ____________________________ Reaction CoordinateFree Energy16reactantproduct230-001 2003 Organic Exam 4-A page - 5 -17. (10 pts) Use combinations of the orbitals of ethylene to construct the four molecular orbitals of butadiene. Label the orbitals X1-X4 with X4 being the highest energy MO. Again just look down on the pi-system from above and draw the orbitals as circles. Energydraw orbitals belowput in energylevel and electronsbelow17use the space above work #17. 18. (10 pts) Explain the following. In the hydrogenation of cyclooctatetraene dienes and trienes are isolated if the reaction is stop before completion. However only benzene and cyclohexane are observed in the incomplete hydrogenation of benzene. Why? ________________________________________________________________________________ ________________________________________________________________________________ Pd(0)/CEtOHH2Pd(0)/CEtOHH2+ 18. (5 pts) How many pi-electrons are there in the following molecule? _______ OO230-001 2003 Organic Exam 4-A page - 6 -Work Space! This page must stay with your exam! You may refer the grader to this page for partial credit.230-001 2003 Organic Exam 4-A page - 7 -Work Space! This page must stay with your exam! You may refer the grader to this page for partial
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