Organic Chemistry Semester 1 LABORATORY MANUAL - Moravian ...

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Mass Spectrometry Appendix D2 Part V. Techniques and Theory Analysis of Mass Spectra. Since all of the peaks in the mass spectra on the previous page occur at masses ≥ the molecular mass of the compound, it seems reasonable to explore the possibility that the lower mass peaks may indicate the after being struck by a high energy electron, these two molecules break up and the peaks give us information on pieces of the original molecule. This “fragmentation process” can be represented by the equation below. After the molecule has been struck by the high energy electron and lost an electron it has a single + charge. So if the molecule fragments, one of the resulting pieces will have the + charge (A + ) and the other piece will have no charge (B.). M + . > A + + B. Mass spectrometers are designed to detect only positively charged particles. So, the mass of A + can be determined from a peak in the mass spectrum of M, but the mass of B.is not detected by the mass spectrometer. However, the masses of A + + B. = the mass of M + , so the mass of B. can be determined by subtracting the mass of the detected peak for A + from the mass of the molecular ion (M + ). Thus, the peak at m/z = 31 in the spectrum above arises from the splitting of the molecular ion into an + ion of mass 31 and a neutral radical of mass 57 (M-31). Often the radical is smaller than the ion and can be identified in the molecular structure more easily. Table 2-77 on p. 103 in Padías gives masses of many common neutral radicals and cations formed from molecular ion fragmentations. Exploration of Mass Spectral Fragmentation Patterns. 1. Look carefully at each of the two spectra on D1 and the 7 additional spectra below and on pp. D3 → D4. Considering the structure of the compound, the brief introduction to mass spectrometry on pp. D1 & D2 and in Padías & CGWW, try to identify the ions whose masses are indicated with a number in each mass spectrum and the bond that broke to form each ion. Assume that the most ions are produced by breakage of only one bond in the original structure. For large mass ion peaks, you may need to use the [M + - (ion peak mass)] value to identify the radical first. You will note that there are other peaks "clustered" around the designated peaks. These peaks often arise from loss of hydrogen atoms or other small particles from the major ion. a. Intensity b. m/z Intensity O m/z
c Part V. Techniques and Theory Appendix D3 Mass Spectrometry c. 58 N Intensity 44 72 M + 87 H m/z d. 41 56 Intensity 55 69 M + 84 m/z e. Intensity 29 43 44 57 M + 72 O H m/z f. O Intensity O CH 3 m/z
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MORAVIAN COLLEGE CHEMISTRY DEPARTME
Page 4 and 5:
Table of Contents (continued) 2 PAR
Page 6 and 7: I. Introduction 4 Fall 2010 Assignm
Page 8 and 9: I. Introduction 6 Fall 2010 Assignm
Page 10 and 11: Part I. Introduction 8 Fall 2010 La
Page 12 and 13: Part I. Introduction 10 Fall 2010 D
Page 14 and 15: Part II. Lab Rules and Regulations
Page 16 and 17: Part II. Lab Rules and Regulations
Page 18 and 19: III Laboratory Records & Report For
Page 24 and 25: Part V. Experiments 22 Fall 2010 Pa
Page 26 and 27: Part V. Experiments 24 Fall 2010 Ex
Page 28 and 29: Part V. Experiments 26 Fall 2010 H
Page 30 and 31: Part V. Experiments 28 Fall 2010 E.
Page 32 and 33: Part V. Experiments 30 Fall 2010 E.
Page 40 and 41: Part V. Experiments 38 Fall 2010
Page 42 and 43: Part V. Experiments 40 Fall 2010 1
Page 45 and 46: Part V. Techniques and Theory Appen
Page 55: Part V. Techniques and Theory Appen
Page 61: Part V. Techniques and Theory Appen
Page 64 and 65: Nuclear Magnetic Resonance Appendix
Page 84: Nuclear Magnetic Resonance Appendix
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Organic Chemistry Semester 1 LABORATORY MANUAL - Moravian ...

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