old exam 1 key

old exam 1 key - E1 CH 12, 13 Since CH 14 was not included...

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E1 CH 12, 13 Since CH 14 was not included on this exam I included an additional quiz over CH 14. I will make a transparency of this exam for review session Feb 3 rd 2008 - 3PM. 1. (12pts) Circle the correct answer or indicate your answer choice for A-D as appropriate. A. The relative population of aligned/non-aligned protons with the magnet cavity of a typical NMR spectrometer is approximately 99/1 75/25 50/50 25/75 1/99 1/999 B. Which methyl group has the largest chemical shift (largest δ value)? CH 3 MgBr CH 3 SSCH 3 (CH 3 ) 3 O + BF 4 - CH 3 Cl C. If one were to examine the 1 H NMR spectrum of 13 C-labeled CH 3 I (i.e. methyl iodide whose carbon is the isotope of carbon, carbon-13), you would expect to see no peaks a singlet a doublet a triplet a quartet D. _______The most intense peak in a mass spectrum is a. the molecular ion b.the most stable ion c. the base peak d.the parent peak e. the ion with the lowest M+1 or M+2 isotopic abundance 2. (6pts) How many nonequivalent carbons would you expect to see in the 13 C NMR spectrum of the compounds shown below? Write your answers on the lines provided. 1 6 7 __________ __________ __________ Br Cl O
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3. (8pts). How many nonequivalent protons would you expect to see in the 1 H NMR spectrum of the compounds shown below? ______ 5 ____ ___ 12 _____ ____ 3 ___ ___ 5 __ 5 if you see diastereo. H’s O O Br Br Br OCH 3 CH 3 O OCH 3 OCH 3 CH 3 O 4. (6pts) What major peaks would you expect to see in the molecular ion region for CH 2 Br 2 ? M:M+2:M+4 at m/z = 172, 174, 176 5. (4pts) On a spectrometer operating at 200 MHz, the 1H NMR signal of CH 3 Cl is separated from TMS by 610 Hz. What is the shift of CH 3 Cl in δ ? ________________ 3.05 _ 6. (6pts) For the structure of ethyl cyanoacetate shown below, state the 1 H-NMR splitting pattern (singlet, doublet, triplet, quartet, quintet, sextet or septet) of the signals for the hydrogens indicated by arrows.
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This note was uploaded on 03/26/2008 for the course CHEM 228 taught by Professor Tichy during the Spring '08 term at Texas A&M.

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old exam 1 key - E1 CH 12, 13 Since CH 14 was not included...

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