Mass Spectrometry and Infrared Spectroscopy

Q Identify the reliable characteristic absorptions in an infrared spectrum, and propose which functional groups are likely to be present in the molecule. 

Q Explain which functional groups cannot be present in a molecule because their characteristic peaks are absent from the IR spectrum. 

Q Given a structure, predict the major ions that will be observed in the mass spectrum from fragmentation of the molecular ion. Use these predictions to determine whether a proposed structure is consistent with the spectrum. 

One of the most important tasks of organic chemistry is the determination of organic structures. When an interesting compound is isolated from a natural source, its structure must be completely determined before a synthesis can begin. Whenever we run a reaction, we must determine whether the product has the desired structure. The structure of an unwanted product must be known so the reaction conditions can be altered to favor the desired product. 

These procedures are insufficient, however, for complex compounds that have never been synthesized and characterized. They are also impractical with compounds that are difficult to obtain, because a relatively large sample is required to complete the elemental analysis and all the functional group tests. We need analytical techniques that work with tiny samples and that do not destroy the sample. 

Fill in the blanks below. To verify that yonr answers are correct, look in your textbook at the end of Chapter 15. Each of the sentences below appears verbatim in the section entitled Review of Concepts and Vocabulary. 

The difference in energy (AE) between vibrational energy levels is determined by the nature of the bond. If a photon of light possesses exactly this amount of energy, the bond can absorb the photon to promote a excitation. 

The location of each signal in an IR spectrum is reported in terms of a frequency-related unit called.  

The waventtmber of each signal is determined primarily by bond and the 

Primary amines exhibit two signals resulting from 

The advent of modern spectroscopic techniques has completely transformed the field of chemistry, and structures can now be determined in several minutes. In this chapter, we will begin to appreciate how spectroscopy - - 

If necessary, review the suggested sections to prepare for this chapter  

In order to understand how spectroscopy is used for structure determination, we must first review some of the basic features of light and matter. 

The perpendicular, oscillating, electric and magnetic fields associated with electromagnetic radiation. 

When viewed as a particle, electromagnetic radiation consists of packets of energy, called photons. The energy of each photon is directly proportional to its frequency. 

In this book, we cover four spectroscopic or related techniques that serve as powerful tools for structure determination in organic chemistry  

Infrared (IR) spectroscopy, covered in this chapter, observes the vibrations of bonds and provides evidence of the functional groups present. 

Ultraviolet (UV) spectroscopy, covered in Chapter 15, observes electronic transitions and provides information on the electronic bonding in the sample. 

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Reaction mechanisms, infrared spectroscopy, and mass spectrometry ... 

There are a variety of analytical methods commonly used for the characterization of neat soap and bar soaps. Many of these methods have been pubUshed as official methods by the American Oil Chemists Society (29). Additionally, many analysts choose United States Pharmacopoeia (USP), British Pharmacopoeia (BP), or Pood Chemical Codex (FCC) methods. These methods tend to be colorimetric, potentiometric, or titrametric procedures. However, a variety of instmmental techniques are also frequendy utilized, eg, gas chromatography, high performance Hquid chromatography, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. 

His researches and those of his pupils led to his formulation in the twenties of the concept of active catalytic centers and the heterogeneity of catalytic and adsorptive surfaces. His catalytic studies were supplemented by researches carried out simultaneously on kinetics of homogeneous gas reactions and photochemistry. The thirties saw Hugh Taylor utilizing more and more of the techniques developed by physicists. Thermal conductivity for ortho-para hydrogen analysis resulted in his use of these species for surface characterization. The discovery of deuterium prompted him to set up production of this isotope by electrolysis on a large scale of several cubic centimeters. This gave him and others a supply of this valuable tracer for catalytic studies. For analysis he invoked not only thermal conductivity, but infrared spectroscopy and mass spectrometry. To ex-... 

In military operations, where CW attack is anticipated as a result of intelligence, detection systems are used which alarm when the presence of one or more identified hazards is detected. A number of physical characteristics of the agents may be used for this, such as ion drift, infrared spectroscopy and mass spectrometry (Box 1). 

Chapter 11 ALKENES INFRARED SPECTROSCOPY AND MASS SPECTROMETRY... 

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