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Exam #2 Chemistry 232 Blackstock July 26, 2007 Name:____________________________(print) Honor Pledge: ______________________________ (sign) You have 90 minutes to complete this exam. Exams are due at 9:30 AM. Partial credit will be given for partially correct answers in most cases, so be sure to show your work. I. General Knowledge & Exam 1 review ( pts)
- (34 pts) Give the structures of the molecules written below and provide the names of any structures shown. allyl alcohol Grignard reagent derived from benzyl bromide ethanol acetal of cyclopentanone Gilman reagent derived from bromobenzene THF Wittig reagent used to prepare styrene product of mCPBA oxidation of trans- 2 - pentene Claisen rearrangement product of allyl vinyl ether disulfide derived from ethane thiol DMSO a monosubstituted benzene which will undergo meta EAS hydrate of benzaldehyde hydrazone of cyclobutanone O O H 2 N NH 2 O O Ph P Ph Ph
I. general knowledge (p1) ______ (34 pts) (p2) ______ (18 pts) II. reactions ______ (29 pts) III. mechanisms ______ (12 pts) IV. synthesis ______ (12 pts) TOTAL ______ (105 pts) (5 pts extra credit)
- (14 pts) (a) (6 pts) One of the most common reactions of aldehydes and ketones is nucleophilic addition to the carbonyl group. An example is acetal formation. Under acidic conditions, write the missing intermediates below for the formation of a hemi-acetal intermediate. Show e-pushing arrows for any step involving nucleophilic attach at the carbonyl. HO OH O H
- (^) (cat) O OH HO hemiacetal (b) (8 pts) Write the intermediates for the next 4 steps to convert the hemiacetal to the product acetal. Show e- pushing arrows for each step except H+^ transfer steps. O OH HO hemiacetal acetal O O
- (4 pts) Give two possible ways of using Grignard chemistry to construct the following alcohol. Show complete reactant structures in each case. OH
IV. Mechanism (12 pts) Provide detailed mechanisms for the transformations given below, showing every step in the process clearly and using electron pushing arrows for all steps except protonations/deprotonations. (a) (6 pts) NH 2 OH, H+^ catalysis N OH
- H 2 O O (b) (6 pts) O O
- 2 H 3 C MgBr
- rxn in ether
- H 3 O+^ H^3 C OH H 3 C OH
V. Synthesis (10 pts) Provide a reaction sequence to accomplish the following conversions (left to right) using any reagents needed to convert the carbons of the starting material into the product structure. Show reactants, products, and necessary reagents for each step in the sequence, but do not show mechanisms here. (1) (6 pts) convert O to O (2) (6 pts) O convert to OH OH
