Mass Spectrometry

James M. Thompson

• Publisher: Jenny Stanford Publishing
• Year: 2017
• ISBN:
  9781351207133
• Edition: 1
• Topic: Ciencias físicas
• Subtopic: Química analítica

It is estimated that there are about 10 million organic chemicals known, and about 100, 000 new organic compounds are produced each year. Some of these new chemicals are made in the laboratory and some are isolated from natural products. The structural determination of these compounds is the job of the chemist. There are several instrumental techniques used to determine the structures of organic compounds. These include NMR, UV/visible, infrared spectroscopy, mass spectrometry, and X-ray crystallography. Of all the instrumental techniques listed, infrared spectroscopy and mass spectrometry are the two most popular techniques, mainly because they tend to be less expensive and give us the most structural information.

This book is an introductory text designed to acquaint undergraduate and graduate students with the basic theory and interpretative techniques of mass spectrometry. Much of the material in this text has been used over a period of several years for teaching courses in materials characterization and chemical analysis. It presents the mass spectra of the major classes of organic compounds and correlates the fragmentation pattern of each spectrum with the structural features of the compound it represents. This has been done for hydrocarbons, organic acids, ketones, aldehydes, esters, anhydrides, phenols, amines, and amides. The text discusses the origin of the fragments, techniques, innovations, and applications in mass spectrometry. It is interspersed with many illustrations, examples, an adequate but not overwhelming bibliography, and problems for students. It will serve as a lecture text for a one-semester course in mass spectrometry or can be used to teach the mass spectra portion of a broader course in material characterization and chemical analysis.

Contents

Preface

Acknowledgments

1 Some Fundamentals of Mass Spectrometry

1.1 Introduction

1.2 The Mass Spectrometer

1.2.1 The Magnetic Sector Mass Spectrometer

1.2.2 The Quadrupole Mass Spectrometer

1.2.3 The Time-of-Flight Mass Spectrometer

1.3 The Mass Spectrum

1.3.1 Ion Fragments

1.3.2 The Base Peak

1.3.3 The Molecular or Parent Ion ( M + )

1.3.4 The (M + 1) + Ion

1.3.5 Isotopic Fragments

1.3.6 High-Resolution Mass Spectrometry

1.4 Depicting Mass Spectral Data

1.5 The Molecular or Parent Ion

1.6 Predicting the Formation of M +

1.7 The Nitrogen Rule

1.8 Metastable Ions

1.9 Doubly Charged Ions

1.10 The General Fragmentation Process

1.11 The Fragmentation of a Hypothetical Molecule

1.12 Identifying the Molecular Ion

1.13 Chemical Ionization

1.14 High-Molecular-Weight Impurities

1.15 The Fragmentation of M +

1.16 Determining the Molecular Ion from the Fragments

1.17 Determining the Molecular Ion by Derivatization

1.18 Determining M + From Rates of Effusion

1.19 General Rearrangement

1.20 Skeletal Rearrangement

1.21 The McLafferty Rearrangement

1.22 The Loss of Neutral Fragments

1.23 Atomic Weight Determinations

1.24 The Isotopes of Carbon

1.25 Calculating Relative Intensities

1.26 The Experimental Determination of the Carbon Number

1.27 Compounds Containing Bromine and/or Chlorine

1.28 Compounds Containing Sulfur

1.29 Beynon’s Table

1.30 Some Techniques, Innovations, and Applications in Mass Spectrometry

1.30.1 Thermogravimetric Analysis–Mass Spectrometry (TG/MS) and Thermogravimetric Analysis–Fourier Transform Infrared (TG/FTIR)

1.30.2 TG/MS Systems

1.30.3 The TG/MS Interface

1.30.4 TG/MS Data Collecting and Processing Software

1.30.5 GC/MS, GC/FTIR and GC/MS/FTIR

1.30.6 The GC/MS and GC/FTIR and GC/MS/FTIR Interfaces

2 The Analysis of Mass Spectra

2.1 The Fragmentation Patterns of Straight-Chain Alkanes

2.2 Branched Alkanes

2.3 Cycloalkanes

2.4 Unsaturated Hydrocarbons

2.5 Alkyl Halides

2.6 Phenyl Halides

2.7 Benzyl Halides

2.8 Aliphatic Ethers

2.9 Alcohols

2.10 Phenols

2.11 Aliphatic Ketones

2.12 Aromatic Ketones

2.13 Aliphatic Aldehydes

2.14 Aromatic Aldehydes

2.15 Anhydrides

2.16 Acetals and Ketals

2.17 Aliphatic Acids

2.18 Aromatic Acids

2.19 Aliphatic Amines

2.20 Aromatic Amines

2.21 Amides

2.22 Aliphatic Nitro Compounds

2.23 Aromatic Nitro Compounds

3 Problems in Mass Spectrometry

3.1 Introduction

3.2 Some General Suggestions for Interpreting Mass Spectra

3.3 Criteria for Finding the Molecular Ion

3.4 Interpretation of a Mass Spectrum Using the National Institute of Standards and Technology (NIST) Mass Spectral Search Program

3.5 Problems

3.6 On the Stability of Molecules

3.6.1 Complex Molecules Revisited

3.7 On Detecting Iodine in the Molecule

3.8 More on Non-Branched Hydrocarbons

3.9 On the Loss of Fragments from the Molecular Ion

3.9.1 Loss of H

3.10 Loss of a methyl group

3.11 Loss of HF from the Molecular Ion

3.12 On the Loss of Water from Alcohols

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