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Infrared Absorbance Spectroscopy

About Infrared Spectroscopy

Infrared spectroscopy provides information about molecular vibrations. Molecules are made from atoms connected by chemical bonds. These atoms can vibrate within this bonding stucture, and those vibrations have specific energies associated with them.

acetone and an alcohol

These energies occur in the infrared region of the electromagnetic spectrum. When infrared light interacts with certain

molecules, specific energies can be absorbed by the molecular vibrations. By measuring the intensity of IR light at various energies after interacting with a sample, we can plot an infrared spectrum.

The spectra on the right show the successful conversion of acetone (a ketone with a C=O group) to an alcohol (with an O-H group) after reaction with a Grignard reagent.

Aspirin IR spectraStudents in Organic Chemistry synthesize aspirin early in the semester, and can use infrared spectroscopy to determine if the synthesis was successful.

KU's Infrared Spectrophotometers

Bruker Tensor 37 FTIR Spectrophotometer with a Pike MIRacle Attenuated Total Reflectance (ATR) sampling attachment

Bruker Tensor

Both of Kutztown University's infrared spectrophotometers are Fourier transform instruments. We have sample holders that allow you to pass IR light directly through a sample. However, sample preparation for this type of spectroscopy can be time consuming. The Attenuated Total Reflectance (ATR) a sampling stage greatly simplifies sample preparation.

Bruker Alpha FTIR with a Diamond ATRBruker Alpha