Detailed information about the infrared absorptions observed for various bonded atoms and groups is usually presented in tabular form. The following table provides a collection of such data for the most common functional groups.

Table of Common IR Absorptions. Note: strong, medium, weak refers to the length of the peak (in the y axis direction). Note: spectra taken by ATR method (used at CSB/SJU) have weaker peaks between 4000-2500 cm -1 compared to reference spectra taken by transmittance methods (typical on SDBS and other sites).

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.

Infrared (IR) Spectroscopy allows the identification of particular bonds present within molecules. In this class we have simplified IR analysis by only focusing on 5 regions of the spectrum.

Hydrocarbons show IR absorption peaks between 2800 and 3300 cm-1 due to C-H stretching vibrations. The hybridization of the carbon affects the exact position of the absorption — stiffer bonds vibrate at higher frequencies. sp3 C-H: 2800-3000, sp2 C-H: 3000-3100, sp C …

Arenes 3028-3087 cm-1 CH) aromatic 2100-1700 cm-1 overtones 1600, 1496, 1461 cm-1 C=C) aromatic 729 i 696 cm-1 CH) arom. bending out of plane Carbonyl compounds ketones

The carbonyl stretching absorption is one of the strongest IR absorptions, and is very useful in structure determination as one can determine both the number of carbonyl groups (assuming …

An IR spectrum is a plot of the percentage of light transmitted (%T) versus the frequency in wavenumbers (ṽ, cm-1). Figure 2 shows the IR spectrum of ethanol (CH3CH2OH).

The use of infrared spectroscopy for determining the substituent pattern of substituted benzene rings is illustrated by the following data, and the spectra examples underneath. Stretching absorptions are marked in blue, bending absprptions in green. The 3000 cm -1 separation between sp 2 and sp 3 C-H stretching modes is clearly evident.

The alkynes can generally be identified with the characteristic weak but sharp IR absorbance bands in the range of 2100-2250 cm -1 due to stretching of the C≡C triple bond, and terminal alkynes can be identified by their absorbance at about 3300 cm -1, due to stretching of sp C-H.