A subscription to JoVE is required to view this content.
IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The absorptions below 1500 cm−1 lie in the fingerprint region resulting from vibrations of the C–C, C–O, and C–N bonds. This region is also called a complex spectra region and is more difficult to analyze. Sometimes spectra of structurally close molecules overlap and are not distinguishable in the diagnostic region. However, they can be distinguished in the fingerprint region since they exhibit a unique pattern of peaks. For instance, O–H and C–H groups of the butanol and propanol show similar stretching absorptions in the diagnostic region but they exhibit a different pattern of peaks in the fingerprint region, which helps distinguish them.
From Chapter 13:
Now Playing
Molecular Vibrational Spectroscopy
644 Views
Molecular Vibrational Spectroscopy
1.3K Views
Molecular Vibrational Spectroscopy
1.7K Views
Molecular Vibrational Spectroscopy
1.1K Views
Molecular Vibrational Spectroscopy
994 Views
Molecular Vibrational Spectroscopy
832 Views
Molecular Vibrational Spectroscopy
591 Views
Molecular Vibrational Spectroscopy
673 Views
Molecular Vibrational Spectroscopy
874 Views
Molecular Vibrational Spectroscopy
724 Views
Molecular Vibrational Spectroscopy
639 Views
Molecular Vibrational Spectroscopy
566 Views
Molecular Vibrational Spectroscopy
595 Views
Molecular Vibrational Spectroscopy
747 Views
Molecular Vibrational Spectroscopy
837 Views
See More
Copyright © 2025 MyJoVE Corporation. All rights reserved
We use cookies to enhance your experience on our website.
By continuing to use our website or clicking “Continue”, you are agreeing to accept our cookies.