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Exam #2 Chemistry 232 Blackstock July 23, 2009 Name:____________________________(print) Honor Pledge: ______________________________ (sign) You have 90 minutes to complete this exam. Exams are due at 7:30 PM. 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 (57 pts)
- (34 pts) Give the complete structures of the molecules named below and the names of any structures shown. an organic acid with pKa = 9.9 malonic acid tosylate formed from R- 2 - pentanol methanol hemiacetal of benzaldehyde reagent to reduce esters to aldehydes (show structure) a Wittig reagent used to prepare styrene chromate ester of isopropanol TMS ether of phenol cyanohydrin of 3-pentanone acetonitrile Claisen rearrangement product of allylphenylether tosylate of benzyl alcohol oxime of cyclohexanone O H 3 C O H O
I. general knowledge (p1) ______ (34 pts) III. mechanisms ______ (14 pts) (p2) ______ (23 pts) IV. synthesis ______ (13 pts) II. reactions ______ (21 pts) TOTAL ______ (105 pts) (5 pts extra credit)
- (9 pts) For imine formation below fill in the product and missing intermediates. Show e-pushing arrows for all steps except proton transfers. NH 2 carbinolamine pH ~ 5 imine weak HA cat O
- (4 pts) Give two possible ways of using Wittig chemistry to construct the following alkene using any phosphonium ylide, aldehyde or ketone needed. Show complete reactant structures in each case.
- (7) It is possible to isomerize an alkene by expoxidation followed by treatment with Ph 3 P. Show the product of the first step and give an e-pushing mechanism for the second step below. mCPBA Ph 3 P + Ph 3 P=O
- (3 pts) True/False and multiple choice (circle one) i. Toward nucleophiles, aldehydes are more reactive than ketones which are more reactive than esters. T F ii. Conversion of an aldehyde to a carboxylic acid is an oxidation. T F iii. An appropriate solvent for PhMgBr reaction with CO 2 would be: ethanol THF AcOH water
IV. Mechanism (14 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)
- Ph MgBr
- H 3 O+ O O 2 in ether OH Ph (^) Ph HO (b) (8 pts) O H OH CH 3 OH, H+ O OCH (^3) + H 2 O
V. Synthesis (13 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) (5 pts) OH convert to (2) (8 pts) convert (^) to CHO O
