Chemistry 221 Exam 4 2010

AUMQIC Exam 4 Chem 22 April 22, 2010 ^ ( Name page c\ r\ 0 3 - 1 (20) 2 (35) total (200) 3 (40) chk 4 (40) 5 (35) 6 (35) Please resist the temptation to deface this space. . 1 (20 points) (a) Draw the most stable enol tautomer (if any) of each carbonyl compound below. ocH ! •4, 1* . (b) Rank the carbonyl compounds above according to the amount of enol present at equilibrium, with 1 indicating the most enol and 4 indicating the least. The third carbonyl compound, 2-methylcyclohexanone, is chiral. Starting with either enantiomer of this ketone, write a mechanism to show how this compound racemizes in the presence of aqueous acid . (c) Fu*)T 2. (20 points) Write the mechanisms of the two reactions below and draw the products. Show + every step explicitly, including all proton transfers; do not use "+H+" and "-H " abbreviations. \o \0 (a ) base-catalyzed hemiacetal hydrolysis cv ( b) base-induced lactone hydrolysis 3. (15 points) Write a mechanism that accounts for the following transformation. Show each step clearly with curved arrows. Hint: no other product is formed in significant yield. 4. (25 points) As promised, here's a problem from the last HW set. Write the complete mechanism, showing every step clearly. > & MS *^0)", A./ O / rs ^ to explain the following reaction. 15 points Write a mechanism . ) 5. ( seen before; methane is produced as a byproduct.) — (This is one that you haven't *, 6. (25 points) Draw the products of the following reactions, including stereochemistry, where relevant. Label products to indicate stereoisomeric relationships as appropriate. 6 O 1 . Ph3P: .A 2. nBu-Li 1 (b) y- >- -78°C »> CH3CH2-I • .N. e Li+ LQ 0 ! NaBD4 EtOH 1 m * . 7 ( 15 points) How would you convert benzyl bromide to the unsaturated ketone below, using only compounds from the Chemical Store (2nd to last page of this exam)? PhCH2Br - C vO. * h 3 o 9 n 8. ( 35 points) Show how you would make the following compounds from malonic ester and any of the other compounds in the Chemical Store . (a ) o < ‘OEt ,C Tt OtCf f & ^ '= -Aww-taf "a>s • 9. (20 points) Suggest a synthesis of the aldehyde below by using only compounds available in the Chemical Store. (a ) y&& & . 10 (15 points) How would you carry out the following transformation? Use any reagents you feel are appropriate. \ u94-l(om ^