infrared spectrophotometry
Quick Summary
Infrared (IR) spectroscopy is a technique used in chemistry to determine the molecular structure of compounds by analyzing how they absorb infrared radiation. Molecules absorb infrared light at specific wavelengths, corresponding to the energy needed to excite their vibrational and rotational states.123
An infrared spectrophotometer passes infrared light through a sample and records the amount of light transmitted at different wavelengths. This creates an infrared spectrum, which is a unique "fingerprint" for each molecule. The absorption peaks in the spectrum, which point downward, indicate the wavelengths of light absorbed by the molecule.13
Different types of bonds and functional groups within a molecule vibrate at characteristic frequencies, leading to absorption bands at specific wavelengths in the IR spectrum. For example, carbon-hydrogen bonds absorb around 3.4 micrometers, and carbon-oxygen double bonds absorb around 5.8 micrometers. By analyzing these absorption patterns, chemists can identify the types of functional groups present and deduce the overall structure of organic compounds.12
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