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What functional groups give the following signals in an IR spectrum? A) 1700 cm-1. B) 1550 cm-1. C) 1700 cm-1 and 2510-3000 cm-1. 2. How can you distinguish the following pairs of compounds through IR analysis? A) CH 3 OH (Methanol) and CH 3 CH 2 OCH 2 CH 3 (Diethylether) B) Cyclopentane and 1-pentene. C) 3. The following spectra is for the ...
21 Οκτ 2024 · Objective. After completing this section, you should be able to use an infrared spectrum to determine the presence of functional groups, such as alcohols, amines and carbonyl groups, in an unknown compound, given a list of infrared absorption frequencies.
By learning where characteristic functional-group absorptions occur, it’s possible to get structural information from IR spectra. Table 12.1 lists the characteristic IR bands of some common functional groups.
IR SPECTRUM OF ALDEHYDES AND KETONES. Carbonyl compounds are those that contain the C=O functional group. In aldehydes, this group is at the end of a carbon chain, whereas in ketones it’s in the middle of the chain.
The broad shape of the absorption band results from the hydrogen bonding of the OH groups between molecules. The OH bond of an alcohol group usually has absorption in the range of 3200–3600 cm-1, while the OH bond of the carboxylic acid group occurs at about 2500–3300 cm-1 (Figure 6.4a and Figure 6.4c).
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?
A few examples reflecting some of the more important functional groups are provided below. Compare them to try to appreciate the subtle differences, comparing frequency, intensity and shape. 1. An alcohol. The characteristic absorption of an alcohol, such as 2-propanol, is the broad band due to the hydrogen bonded -OH group around 3200-3400 cm -1.
