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Chad breaks down how Infrared Spectroscopy can be used to determine a molecule's functional groups. Chad includes a chart of common IR absorptions.
When analyzing an IR spectrum, it is helpful to overlay the diagram below onto the spectrum with our mind to help recognize functional groups. Figure 1. Group frequency and fingerprint regions of the mid-infrared spectrum
Identifying Functional Groups from an IR Spectrum. The IR spectrum of an unknown compound is shown in Figure 12.28. What functional groups does the compound contain?
The inside cover of the Wade textbook has a table of functional groups, and they are discussed in detail in ch. 2, pages 68 – 74 of the 6th edition. A table relating IR frequencies to specific covalent bonds can be found on p. 851 of your laboratory textbook.
Table of Characteristic IR Absorptions m=medium, w=weak, s=strong, n=narrow, b=broad, sh=sharp ... –1 bond functional group 3640–3610 (s, sh) O–H stretch, free hydroxyl alcohols, phenols 3500–3200 (s,b) O–H stretch, H–bonded alcohols, phenols 3400–3250 (m) N–H stretch 1˚, 2˚ amines, amides 3300–2500 (m) O–H stretch ...
Be able to analyze an IR spectrum for important functional group bands. With the basic understanding of the IR theory, we will take a look at the actual output from IR spectroscopy experiments, and learn how to get structural information from IR spectrum.
Infrared spectroscopy is the study of the interaction of infrared light with matter. The fundamental measurement obtained in infrared spectroscopy is an infrared spectrum, which is a plot of measured infrared intensity versus wavelength (or frequency) of light.
