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
607 Views
Molecular Vibrational Spectroscopy
1.2K Views
Molecular Vibrational Spectroscopy
1.6K Views
Molecular Vibrational Spectroscopy
972 Views
Molecular Vibrational Spectroscopy
925 Views
Molecular Vibrational Spectroscopy
771 Views
Molecular Vibrational Spectroscopy
555 Views
Molecular Vibrational Spectroscopy
624 Views
Molecular Vibrational Spectroscopy
846 Views
Molecular Vibrational Spectroscopy
699 Views
Molecular Vibrational Spectroscopy
605 Views
Molecular Vibrational Spectroscopy
547 Views
Molecular Vibrational Spectroscopy
566 Views
Molecular Vibrational Spectroscopy
710 Views
Molecular Vibrational Spectroscopy
791 Views
See More
Copyright © 2025 MyJoVE Corporation. All rights reserved