Key Concepts—Mass Spectrometry and Infrared Spectroscopy

Mass spectrometry and IR spectroscopy give valuable but limited information on the identity of an unknown. Although the mass spectral and IR data reveal that X has a molecular formula of C4Hg02 and contains a carbonyl group, more data are needed to determine its complete structure. In Chapter 14, we will learn how other spectroscopic data can be used for that purpose. 

Which of the following possible structures for X can be excluded on the basis of its IR spectrum (a) CH3COOCH2CH3 (b) HOCH2CH2CH2CHO (c) CH3CH2COOCH3 (d) CH3CH2CH2COOH  

The higher the percent s-character, the stronger the bond, and the higher the of an IR absorption. 

18 Which compound gives a molecular ion at m/z = 122 C6H5CH2CH2CH3, C6H5COCH2CH3, or C6H5OCH2CH3  

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