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MT1_Wi00 - Exact Masses and Isotopic Abundances of Several...

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Unformatted text preview: Exact Masses and Isotopic Abundances of Several Isotopes Important in Mass Spectrometry ....................................................................... ................... OMTI ”MOO Element Isotope Exact mass Abundance, 96 ab'.’..5+:.-.;.:ih§%£f§u. ting/.17.; » . 1 «21916;: a: ufiuix‘ige ran-r dv‘i -:‘;&L\.m3~£ a. .. ,« hydrogen ‘1-1 1.007825 99.985 deuterium 2H 2.0140 0.015 . carbon ”C 12.0000 98.90 13C 13.00335 1.10 nitrogen MN 14.00307 99.63 l5N 15.00011 0.37 oxygen 1"’0 15.99491 99.759 170 16.99913 0.037 100 17.99916 0.204 fluorine ”F 18.99840 100. silicon 2"Si 27.97693 92.21 If you prefer to use a fmulcl 29Si 28.97649 4.67 elemem of u r 3°51 29.97377 3.10 “50'” °2C"°'+' 2 _ H phosphorus 3'P 30.97376 100. . 2 C = number of carbons sulfur 3IS 31.97207 95.0 H = number of hydrogens 33s 32.97146 0.75 “S 3396787 4’22 a double bond = one element of unsaturation Chlorine 35C] 34-96385 75-77 a ring = one element of unsaturation 37 - ' Cl 3696590 24.23 a tnple bond = two elements of unsaturation bromine 7"lBr 78.91834 50.69 “3' 30-91629 49-31 Halogens. Halogens simply substitute for hydrogen atoms in the molecular for- iodine 1271 12630447 100. ................................................................ mula. The formula C2116 is saturated, so the formula C2H4F2 is also saturated. C4113 has one element of unsaturation, and C4H5Br3 also has one element of unsaturation. In calculating the number of elements of unsaturation, simply count halogens as hydrogen atoms. $112—$Br2 CHJ—Cl'in CH3—CH=CH—CBI3 CHz—CHBI' saturated one element of unsaturation one element of unsaturation Oxygen. An oxygen atom can be added to the chain without changing the number of hydrogen atoms or carbon atoms. In calculating the number of elements of unsaturation. ignore the oxygen atoms. 0 o H / \ Cl‘l3—Cl-l3 Clrl3—O—CH3 CH3—C—H or Cl'lz—CH2 C2116. saturated C2H60, saturated CZH.O, one element of unsaturation Nitrogen. A nitrogen atom can take the place of a carbon atom in the chain, but nitrogen is trivalent, having only one additional hydrogen atom, compared with two. hydrogens for each additional carbon atom. In computing the elements of unsatura-, tion, count nitrogen as half a carbon atom. IlIllll Willi?” HHHHH / carbon + 2 H nitrogen + l H NU, Winter 2000 2 1. (20 pts) The infrared and proton magnetic resonance spectra for a compound K, C9H120, are given below. Propose a structure for K that will fit all the spectroscopic data. Explain your reasoning in less than 50 words by pointing out relevant spectroscopic assignments in the spectra . (To save time, you may choose to draw/functional groups on top of the spectra as part ofyoar logic). MP C9H12° MW 136 ‘/. IRMSHIY VME Copyright © 1994 5H 8. 7. 7. PHI 4. 3. 3. 2. 2. 1. PPM 1.0 NU, Winter 2000 3 2. (20 pts) The infrared, proton magnetic resonance, and mass spectra for compound M, C5H100, are shown below. Propose a structure for M that will fit all the spectroscopic data. Explain your reasoning in less than 50 words by pointing out all relevant spectroscopic assignments in the spectra . (To save time, you may choose to drawfunctional groups on top of the spectra as part ofyour logic).As a part of your explanation, draw the structures of the cationic species that occurs at 43, 71, and 86 in the mass Specuum' MS data: CSHWO 43 Intensitg 86 '71 30405050708090100110120131140150100173130190200 mfe 13C NMR data: q—22.0; q-16.7; d-45t2; 5—2102 1H NMR data: IR data: 1 Wave Number. cni 4030 3WD 2500 2WD 1500 130012001100 "no 900 H30 703 s 4 s 6 ? 3 9 10 Walength microns H 12 13 14 ‘5 NU, Winter 2000 4 3. The mass spectra for two compounds L, and O are shown below. Propose reasonable structures for L and 0. As a part of your explanation, draw the structures of the cationic species that give the “starred” peaks. CngoO 3 'G C 3 5 so 40 so 60 m an 90 monoimuomoisomm 130190200 mfe CsHaoz 43* 3 E :2 X E 57 "k 584: “’0 304050607080m100110120130m31901801nlm1932m m/e NU, Winter 2000 5 4. (20 pts) The infrared, proton magnetic resonance, and mass spectra for compound N, CngoOz, are shown below. Propose a structure for N that will fit all the spectroscopic data. Explain your reasoning in less than 50 words by pointing out all relevant spectroscopic assignments in the spectra . (To save time, you may choose to drawfunctional groups on top of the spectra as part ofyour logic).As a part of your explanation, draw the structures of the cationic species that occurs at 121, 137, and 138 in the mass spectrum. MS data: Cusoa Intensity so 40 so an 70 ac 90100110120131143190180111180193200 mi’e 13C NMR data: q-56.0; t-71.0; d-114.3; d-128.3; 5-1609; 5-1332 1H NMR data: IR data: Wave Nun'ber. erri1 41130 3000 2530 2WD 1WD 130012001100 1WD 91) am 700 3 4 5 B 7 8 9 10 11 12 18 14 15 Wavelength microns NU, Winter 2000 5. a (l6 pts) From cyclohexanone synthesize the following molecule. Pay attention to the relative regiochemistry as indicated. You may use any deuterium—containing reagent (deuterium is an isotope of H), any organic reagent containing two carbon or less and any inorganic reagents. 0 Br multistep synthesis ———————————> b) (4 pts) How would you modify your synthesis in a) so that with the same number of steps you will D get the other regioisomer, Br ? ...
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