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Answer key to Exam 1

Answer key to Exam 1 - Multiple Choice 3 points each 1 The...

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Unformatted text preview: Multiple Choice: 3 points each 1. The IR peak that distinguishes 3. 1° amine and a 1° amide is at cm'l. @450 and 3350 (two peaks) b. 2200 c. 1650 d. 1350 2. Which of the following techniques can readily distinguish between CH3COOCH2CH3 and CH300CCH2CH3? IR lH NMR 13C NMR Mass Spectrometry A B C D a.CandD @B,CandD c.allbutB d.AandC 1) \ 3. Which of the following compounds shows two singlets at 1.3 and 2.1 ppm with a corresponding relative integration ratio of 3:1 in 1H NMR. a. ongooccxcm)3 b. (CH3O)2C=C(OCH3)2 @CH3COOC(CH3)3 d. CH3COCH2CH2COCH3 4. Addition of H20/I-I+ to styrene (PhCH=CH2) will form a compound that will show a peak at cm" on an IR spectrum. a. 1740 ® 3300 c. 1695 d. 1050 5. The molecular ion cluster of a compound shows the following M+/(M+2)/M+4) with a relative ratio of intensities 1:2: 1. The molecular formula of the compound contains atoms. a. one nitrogen b. one bromine 0. two chlorine @ two bromine 6. Which of the following methyl groups will show the most downfield 1H NMR chemical shift? a. CH3I @CHgOH c. CH3COCH3 d. CH3CH3 7. Using a 60 MHz spectrometer, the protons in dichloromethane appear at 5.30 ppm. When the same sample is placed in a 100 MHz instrument, where does the signal appear? a. 8.33 ppm .530 ppm c. 3.18 ppm d. cannot be determined from the information given 8. What is the approximate shift of an alkenyl carbon in 13C NMR? a. 10 ppm b. 30 ppm 0. 70 ppm ((1)120 ppm e. 200 ppm 9. Which of the following fragment peaks would not be present in the mass spectrum of n-hexane? a. 37 (1971 c. 57 d. 43 3. 29 10. What effect does conjugation typically have on the frequency at which absorption by C=O occurs? Q Conjugation decreases the frequency at which absorption occurs. b. Conjugation increases the frequency at which absorption occurs. c. Conjugation does not affect the frequency at which absorption occurs. Short Answer and Spectral Problems: 70 points 11. Explain how the peaks at m/z 115, 101 and 73 arise in the mass spectrum of 3- methyl-3-heptanol. Use arrow formalism to show how these fragments an'se. W\ m-‘S W A- CH3' (. . 9}“ '02“ "filer“5 m-‘L‘i W I (“~57 20.1.“ \2) N A \4/\ ._o"' mIL 47) “VI ’7 \ w w ‘5 ’ a- 0 / * ‘h 63’ -\>‘ Mitt "°’ 12. Explain how mass spectrometry could be used to distinguish between these compounds. Show the major fragments that would be formed. 2‘14 iv 13. Suggest a structure for the compound with following data: M+ at m/z 60 11 10 9 B 7 6 5 4 3 Z 1 0 rakes—2:4 ppm m, 1H s, 1H d, 6H 14. Suggest a structure for the compound with following data: IHNMR 4.3, q, 2H 3.8, s, 2H 1.3, t, 3H 100 flS-IU 3417 80 01 0 Relative Intensity A O 20 20 4O 60 80 100 120 140 160 180 200 220 15. This compound has the molecular formula C9H11N02. Using the following IR, 1H NMR and 13C NMR propose a structure for this molecule. M'I’LW : I 1/ nun! nun \- E O ‘/\ ‘: L ,. \/ C"OC|J~L_CH 9 8 7 6 5 4 3 2 1 0 m—m ppm splitting d std q s t integration 1 1 l l 2 2 3 200 180 160 140 120 1.00 80 60 40 20 0 ans-cm: m'n 16. Determine the structure of a compound with the molecular formula C10H1202. In addition to the infrared spectrum, 'H NMR, and 13C NMR and DEPT NMR spectral data. - MZlW, Sf ”Z.— _ 9 8 7 6 5 4 3 2 1 0 “9-42-74: Ppm 09‘) 59‘1- L90 splitting t d d t s s 5 integration 1 1 1 1 3 2 3 200 180 160 140 120 100 80 60 40 20 O ens-m m 17. What spectrum would you expect for diethylamine, CH3CH2NHCH2CH3? etch it below. Give chemical shifts, splitting, and integrals for the signals. (a “l \ W\ J 1 \ O a ‘E> 7 3" 5 ‘5 BONUS: Suggest a structure for the compound with the following spectral data: 100 mwmus 0) on O 0 Relative Intensity A 0 /® 6—? O 25 50 75 100 125 / ofi HEP-0347! ppm integration 2 2 3 [ACILFAVLK’] P \ II 3 "-‘C NMR(gpm1 [717/ 153 . 35 113 .54 62. 90 24 . 80 13 . 9'7 alumnus- I ...
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