Solved Exam for Organic Chemistry II: Reactivity, Synthesis, and Spectroscopy | CHEM 30B, Exams of Organic Chemistry

Download Solved Exam for Organic Chemistry II: Reactivity, Synthesis, and Spectroscopy | CHEM 30B and more Exams Organic Chemistry in PDF only on Docsity! Chem 30B Winter 2004 Final Exam – Part B Solutions Page 1 Statistics: High score = 99 Average = 69.1 Low score = 09 Standard Deviation = irrelevant as it does not control grade distribution in this class. A note about exam keys: The answers presented here are usually significantly longer than expected from a student taking the exam. An exam key serves not only to reveal what was expected, but to instruct you as well. To see the final course grade cutoffs, consult the grading scale on the Chem 30B course web page. 1. CH2OH CO2H CO2CH3 HO CrO3 aq. H2SO4 CH3OH H2SO4 1. H2C=CHMgBr (excess) 2. H3O+ 2. H2N NH2 O 3. The molecular force that has the greatest influence on your choice in question 2 is hydrogen bonding. This force is typically about 5 kcal mol-1. Another, very weak molecular force that also influences boiling point of this compound is van der Waals forces. 4. Highly soluble. 5. (a) 1. CH3MgCl 2. aq. H2SO4H O OH (b) CH3O O PhNH2 H3O+ PhN O H Chem 30B Winter 2004 Final Exam – Part B Solutions Page 2 6. Retrosynthesis: Ph O O Ph Ph OH O + Ph OH Fischer esterification LiAlH4 Ph OH O Grignard/CO2 PhBr Forward direction: PhBr 1. Mg, ether 2. CO2 3. H3O+ PhCO2H 1. LiAlH4 2. H3O+ PhCH2OH PhCO2H + PhCH2OH H2SO4 PhCO2CH2Ph 7. OO O CH3O OCH3 CH3O O CH3O O O CH3O O H3C I 8. (a) Epoxides are more reactive than other ethers due to ring strain. (b) Alkoxides are good nucleophiles because they have negative charge on oxygen. 9. Fate #1: Accept nucleophile at carbon. A ketone is more electrophilic than an ester. O OO OH O O O OH Fate #2: Accept electrophile (usually “H+”) at oxygen. Protonation of the ester affords a conjugate acid with significant resonance stabilization. The protonated ketone does not have significant resonance stabilization. O OO H OH2 O OHO Fate #3: Deprotonate α-carbon to form enolate. O OO H OH O OO