Organic Chemistry Semester 1 LABORATORY MANUAL - Moravian ...

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Part V. Experiments 36 Fall 2010 Experiment 7 Part A Intensity How Can We Determine the Structure of an <strong>Organic</strong> Compound B. Pre-lab Preparation Assignment: 1. Read: This handout 2. Read: Lab Manual Part V. Appendix D1. Padías pp. 98-102 3. Read the Mass Spectrometry Background Introduction to Mass Spectrometry links on the Experiment 7A page of the course website. 4. Work Through: The Introduction to Mass Spectrometry and Structural Analysis activity below and be ready to respond to the questions at the bottom of the last page. 5. Complete the electronic Prelab Questions (course website) by 8:00 PM, Monday, November 1 on the Course Blackboard Site as explained on the Course Information page. 6. Consider possible claims and warrants for the QOW (See below) 7. In your lab notebook: (See Lab Manual pp. 15-17 for format.) a. Enter the title of the experiment, name of group members and QOW on the appropriate first left-hand page. b. Up-date the Table of Contents. 7. Bring your notebook and your initial claims and warrants concerning the QOW to the AM lab discussion period on Tuesday, November 2. B. Objectives: 1. To gain experience with collecting mass spectra of solid compounds. 2. To gain expertise with analyzing IR and mass spectral data to determine the structure of organic compounds. C. Question of the Day: How Do <strong>Organic</strong> Compounds Interact with High Energy Electrons and What Structural Information Can We Obtain from the Results D. Key Terms/concepts/techniques: • Mass spectrometry • Base Peak • Molecular ion E. Introduction to Mass Spectrometry and Structural Analysis 1. The Mass Selective Detector (MSD). When a neutral substance enters that mass spectrometer, it is bombarded with an electron, which causes the substance to ionize as illustrated in Equation 1. e - + M [M] + . + 2 e - Equation 1: Electron Impact Ionization
Fall 2010 37 Part IV. Experiments The species M is both a cation (has a positive charge) and a free radical (has an unpaired electron) and is referred to as a radical cation. The mass of this first formed radical cation is equal to that of the original molecule entering the mass spectrometer and is referred to as the molecular ion. The molecular ion, because it retains considerable energy from the initial collision, will tend to break down (fragment) into smaller fragments. These fragmentations usually result from breakage of one bond dividing the original structure into two pieces one having a positive charge (a cation) and the other containing the unpaired electron (a free radical). The mass spectrometer detects only the positive ions and not the free radicals. 2. Characteristics of Mass Spectra. For our purposes in this activity it is important to know the following: a. The mass spectrometer detects only positive ions and separates them on the according to their mass to charge ratio, m/z. b. Most ions produced on ionization in the electron beam are uni-positive so numerically, m/z = mass. c. The mass of the molecular ion can usually be taken as the molecular weight of the substance. d. The mass spectrometer can separate ions that have different isotopes of their atoms. e. The most intense peak in the spectrum is called the base peak and represents the ion of highest abundance and therefore the highest intensity. f. Knowledge of the isotope composition of the more common elements is essential to the interpretation of mass spectral data. See Figure 1 Figure 1: Table of Isotope Composition of Some Common Elements 3. Initial Analysis of Molecular Ions. a. Detection of Halogens in Compounds from Molecular Ions: • The presence of bromine in a compound leads to two molecular ions (with 35 Br 79 or with 35 Br 81 ) differing by 2 mass units. For a molecule with one bromine atom, what should be the relative intensities of these two molecular ions
Page 1: 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 57 and 58: c Part V. Techniques and Theory App
Page 61: Part V. Techniques and Theory Appen
Page 64 and 65: Nuclear Magnetic Resonance Appendix
Page 84: Nuclear Magnetic Resonance Appendix

Organic Chemistry Semester 1 LABORATORY MANUAL - Moravian ...

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