Structure Determination Mass Spectrometry and Infrared Spectroscopy

Structure Determination Mass Spectrometry and Infrared Spectroscopy 

ThomsonNOW Throughout this chapter, sign in at www.thomsonedu.com for online self-study and interactive tutorials based on your level of understanding. 

Online homework for this chapter may be assigned in Organic OWL. 

Practically everything vveVe said in previous chapters has been stated without any proof. We said in Section 6.8, for instance, that Markovnikov s rule is followed in alkene electrophilic addition reactions and that treatment of 1-butene with HCI yields 2-chlorobutane rather than 1-chlorobutane. Similarly, we said in Section 11.7 that Zaitsev s rule is followed in elimination reactions and that treatment of 2-chlorobutane with NaOH yields 2-butene rather than 1-butene. But how do w e know that these statements are correct The answer to these and many thousands of similar questions is that the structures of the reaction products have been determined experimentally. 

Determining the structure of an organic compound was a difficult and time-consuming process in the 19th and early 20tli centuries, but powerful techniques are now available that greatly simplify the problem. In this and the next chapter, we ll look at four such techniques—mass spectrometry (MS), infrared (IR) spectroscopy, ultraviolet spectroscopy (UVO and nuclear magnetic resonance spectroscopy (NMR)—and we ll see the kind of information that can be obtained from each. 

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Infrared spectroscopy What functional groups are present Ultraviolet spectroscopy Is a conjugated it electron system present  

Nuclear magnetic What is the carbon-hydrogen framework  

At its simplest, mass spectrometry (MS) is a technique for measuring the mass, and therefore the molecular weight (MW), of a molecule. In addition. 

Fragmentation patterns of common functional groups (Section 12.3). a. Alcohols. 

Mass spectrometry in biological systems TOF instruments (Section 12.4). 

Time-of-flight instruments are used to produce charged molecules with little fragmentation. 

The samples are focused into a small packet and given a burst of energy. 

Each molecule moves at a velocity that depends on the square root of its mass. 

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CHAPTER 12 Structure Determination Mass Spectrometry and Infrared Spectroscopy... 

Chapter 12, Structure Determination Mass Spectrometry and Infrared Spectroscopy—A new Section 12.4 discusses mass spectrometry of biological molecules, focusing on time-of-flight instruments and soft ionization methods such as MAI.DI. 

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