Study Set Content:
This region typically ranges from around 4000 cm^-1 to
1500 cm^-1. It contains absorption bands that are characteristic of functional groups
present in the molecule.
Functional Group Regi
This region, below 1000 cm^-1, is more complex and harder to
assign. It contains unique spectral features that can be used for identifying specific
compounds.
Fingerprint Region:
KEY NOTES:
• Most analytical applications of IR spectroscopy are focused on the ____
because absorption of organic molecules is high in this region. This region is commonly
used for structural confirmation and identification of organic compounds.
middle IR region
Near-Infrared Spectrophotometry: While the middle-infrared region is commonly used for structural confirmation, ____ is also utilized, particularly for quality control purposes in industries such as food processing.
near-infrared spectrophotometry
PRINCIPLE OF IR
•
The portion of the infrared region most useful for analysis of organic compounds have a wavelength range from ____, with a corresponding frequency range from 1.9*1013 to 1.2*1014 Hz.
2,500 to 16,000 nm
When the frequency of the IR radiation is equal to the natural frequency of the vibration, the molecule absorbs
IR radiation.
Absorption of IR radiation causes an excitation of molecules from a lower to the higher
vibrational level.
Each vibrational level is associated with a number closely placed
rotational level.
IR radiation causes the excitation of the vibrations of covalent bonds within that molecule. These vibrations include the stretching and bending modes.
MOLECULAR VIBRATIONS
distance bet two atoms increases or decreases
Stretching
Stretching
Symmetrical and Asymmetrical
