Midterm 4 Key

Midterm 4 Key - Name: page 1 Chemistry C3443 Fall 2004...

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Unformatted text preview: Name: page 1 Chemistry C3443 Fall 2004 Midterm #4 75 minutes December 6, 2004 Instructions: (1) For some questions, you have a choice of which problem(s) to answer. For these, cross out (X) answers you do not want counted. (2) Notice that for each question, we have suggested how much time you spend on that question and indicated how many points it is worth. We suggest that you first go through the entire exam and answer the questions that are easier for you and then go back to the questions that are harder f0r you. (3) Put your name at the top of each page. (4) Unless indicated otherwise, all structures should be skeletal (line) drawings. The exam contains ll pages (including this face page). The total number of points is 100. P’N!‘ TOTAL: / 100 Name: page 2 I. Ethylene has a strong absorption in the ultraviolet region, while ethane does not. Using molecular orbital diagrams, explain this observation. (10 minutes, 20 points total) —~ W l 1w M l l —‘ H a l l i l : L .3. '3— _— Err—4756195 CTHANC A — -r T -' 4 CORTLCSPol—‘OS To THC 774477“ TIL/Qr-JSZTICDN. ETNARC HAS NO 77“ MOLECULAF— QABIT/Jgf) ANO 7H:— 5-__.. 0—): rLAHSIrION :5 oT MuCH HIGHS/L ENC/L67 So Woupb AGJOILB 3 6w:le IN A DI'HEKEW REG-TO" 0" THO” Euccrkoflflorxcmrc SPECTAu/v Name: page 3 II. For each of the reactions shown below, fill in the box with the appropriate reagent, major product or starting material. For reagents, number (1), (2), etc. if more than one transformation is required. Also, make sure to include solvent and bases if appropriate. If NO REACTION occurs, write “NR”. Choose 2 of the 3 problems. (10 minutes, 20 points total) (1) ~ H H3C—E-CH3 /=/C 3 NH 3 H3C (2) C12 —— HCl ————>- (3) hv, NBS Br / —————> CCl4 /l\/\ Name: page 4 III. You react benzyl bromide A with an ethyl Grignard Reagent to give propylbenzene B. You characterize both the starting material and product by 1H NMR. (1) Assign the lH NMR spectra on this and the next page to either the starting material A or product B. Provide a brief explanation for each of your assignments (refer to 2 key peaks in your explanation for each spectrum). (2) Based on the 1H NMR spectra and referring to at least 3 key peaks, explain how you can tell the reaction was successful. Your explanation should account for any changes in the spectra for the benzylic protons. Also, your explanation should explain how you know that only 1 eq. of the ethyl group added to the benzyl bromide. I (15 minutes, 30 points total) ,2 CL Br WITHDRAwfi e- DEJSIT‘f so DOWNSHIELD ) HSP-OZ-210 .‘r 1 1 10 9 8 7 6 S 4 3 2 1 0 HSP-flfl—BSZ ppm Name: page 6 IV. Propose a sequence of reactions that will allow you to accomplish the transformation shown below. You may use any compounds containing zero, one, or two carbon atoms. Your answer should be given in standard "synthetic" notation, i.e., starting material, arrow with reagent, first synthetic intermediate, arrow with second reagent, second synthetic intermediate, arrow with third reagent, etc. HINT: Even if you are not sure of the entire answer, work in the forward and reverse directions for partial credit. Choose 1 of the 2 problems. (15 nu'nutes, 30 points total) (1) ——-——> /\/\/C02H HOZC 6m in) ) O/L 6r Name: IVL confinued (2) I) [5H3 -er 1) HOCNJJ %H OH fli/ page 7 ...
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This test prep was uploaded on 04/07/2008 for the course CHEM C3443 taught by Professor Cornish during the Fall '08 term at Columbia.

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Midterm 4 Key - Name: page 1 Chemistry C3443 Fall 2004...

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