Name:___________________________ Student ID# ___________________________ CH 231 Test 4 Chapters 10, 11 (Nov. 28, 2006) ? You have 105 minutes to complete the exam. 1.(10 pts) How would you conduct the following transformations using an organocopper coupling reaction? More than one step is required in each case. (It is not necessary to show how any necessary Gilman reagents are prepared, just assume that they are commercially available.) steps? steps? Score:_______/100 Combined Avg. through Test IV:_________% 2. (6 pts) State whether each of the following reactions is an oxidation or a reduction of the organic substrate. OH PCC O H O H 2 N O N H Br 1. Mg, Et 2 O 2. H 2 O 3. (8 pts) Draw the chemical structure of each molecule named below: Tosylate Thionyl Chloride THF (Tetrahydrofuran) DMF (N,N-Dimethylformamide) Chloroform Acetonitrile Pyridine Methylene Chloride 4. (12 pts) Provide complete electron-pushing mechanisms for the reaction steps shown: 1. NBS, h? 2. ???, DMSO 5. (18 pts) Supply the missing reactant, reagent(s), or products in the schemes below. Indicate stereochemistry when appropriate. If more than one major product is expected, show each one anticipated. If no reaction is expected, write NR. NaI, O Cl A. B. TsO H KOH, DMSO, H 2 O C. I D. Br NaNH 2 , THF Cl SOCl 2 , Py E. OH F. G. H. I. cat. HCl, EtOH Br OMe OH AcOH (acetic acid) OTs [Cl - ] too low to form an alkyl chloride as a major product 6.(9 pts) Which substance in each of the following pairs is a better nucleophile? Explain your choices in 20 words or less. A. (CH 3 ) 2 N - or (CH 3 ) 2 NH B. (CH 3 ) 3 N or (CH 3 ) 3 B C. H 2 S or H 2 O 7.(8 pts) Briefly explain why iodocyclohexane gives different amounts of substitution and elimination products when the nucleophile/base is changed from acetate ( - OAc or CH 3 COO - ) to ethoxide ( - OEt or CH 3 CH 2 O - ). Be sure to include any pertinent solvent effects in your brief explanation. I NaOAc, DMSO OAc only NaOEt, EtOH OEt < 10 % > 90% 8. (15 pts) The tosylate of (2R,3S)-3-phenyl-2-butanol undergoes an E2 reaction on treatment with base to yield 2-phenyl-2-butene. What is the stereochemistry of the product alkene? Draw the major product, including the correct alkene geometry, and rationalize the stereoselectivity using a Newman projection of the reactive conformer. OTs Base E2 Product alkene stereochemistry is not necessarily as shown. Predict the alkene geometry using a Newman projection. 9. (14 pts) Consider the following statements with respect to S N 1, S N 2, E1, and E2 reactions. To which mechanism(s), if any, does each statement apply? (Note: no partial credit here, each statement is worth 1 pt and requires all of the applicable mechanisms.) a. Rearrangements are possible b. Accelerated by protic solvents c. Accelerated by polar aprotic solvents d. Accelerated by nonpolar solvents e. Substitution at a chirality center results in racemization f. First order in substrate (be careful?.) g. Involves a carbocationic intermediate h. Is a concerted reaction process (no intermediate) i. Substitution at a chirality center results in inversion of stereochemistry (assuming substrate priorities remain the same) j. Substitution at a chirality center results in retention of configuration w/ little or no erosion of optical purity (assuming substrate priorities remain the same) k. First order in base or nucleophile l. Order of reactivity of haloalkanes is 3 o > 2 o > 1 o m. All such mechanisms require one of two particular conformations Dr. Timothy Snowden CH 231 Test 1
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