Chem 238 Final Exam

CHEM 238 Winter, 2001 FINAL EXAM Name Prof. Sasaki Please circle your TA: Dirk Schweitzer , Tyan Carter, Carla McDowell 175 points TOTAL Good Luck! Note: Only answers in the box will be graded. _______________________________________________________________________ _ 1. (30) (a) Draw a stepwise mechanism for the following reaction. Use curved arrows to indicate the movement of electrons. O O H3 C H+ HO OH CH3 O H3 C O CH3 O . (b) Briefly explain the fact that, although hemiacetal formation between methanol and cyclohexanone is thermodynamically disfavored, addition of methanol to cyclopropane goes essentially to completion.O CH3OH HO OCH3 O , cyclopropanone cyclohexanone CHEM 238 page 2 Name . 2. (35) A ? , ? -unsaturated carbonyl compound rearranges to a more stable conjugated ? ,? -unsaturated compound in the presence of either acid or base. O H+ or OHO A ! ,†-unsaturated carbonyl compound A #,! -unsaturated carbonyl compound (a) Propose a mechanism for the base-catalyzed rea rrangement. (b) Propose a mechanism for the acid-catalyzed rearrangement. CHEM 238 page 3 Name . 3. (35) Predict the structures of the products or starting materials in the following equations.Show stereochemistry when it is known. (a) O P + CH3 (b) H3 CO 1) BH3 :THF 2) H2 O2 , OH- (c) H3 C 1) Mg, THF H3 CO Br 2) D2 O (d) O H3 C O H N CH3 HNO3 H2 SO4 (e) O O O 1) NH2 -NH2 2) NaOH, heat CHEM 238 page 4 Name . 4. (35) (a) Provide a reasonable synthesis for the following compounds from the indicated materials. You may use any reagents that you wish to use. (a) CH2 OH from CH2 OH CH3 CH2 O O OCH2 CH3 and compounds with 4 carbons or less O (b) O from benzene and any compounds with 2 carbons or less.CHEM 238 page 5 Name . 5. (35) A number of plants produce chemical substances that prevent insects from feeding on them. Some steps in the synthesis of such a compound, called an antifeedant, are shown bellow. Supply reagents for the transformations. (The wavy lines indicate either that stereo chemistry is not known or that a mixture of stereoisomers may exist. ) H3 C O H3 C O O A H3 C H3 C B H3 C H3 CO O OH H C H3 CO O D H3 C H CH2 H3 C H3 CO O EtO- Na+ EtOH H3 C H3 CO O O H O H E H3 C O H3 C H CH2 A: B: C: D: E: