• Question: What is infared spectroscopy?

    Asked by Hilary to Baljit, Jesus, Michael on 19 Nov 2015.
    • Photo: Jesus Calvo-Castro

      Jesus Calvo-Castro answered on 19 Nov 2015:

      Hi @Hilary. IR spectroscopy is a technique which is normally use to determine which functional groups are present in your molecule. The way the instrument operates is by monitoring changes in the dipole moments. When a bond is formed by two elements of different electronegativities, there is a dipole where the negative pole located on the most electronegative atom (since the electron would prefer to be allocated close to this one). The energy used in IR spectroscopy is enough to induce vibrations (changes in position) of the different atoms and therefore make changes to the dipole moments. Because the energy required to make a certain bond vibrate is known, we can identify (often using tables) which functional groups are present.

    • Photo: Baljit Ghatora

      Baljit Ghatora answered on 19 Nov 2015:

      @hilary- infrared spectroscopy in the simplest terms looks at vibrations (stretching and bending) in a substance. When a substance is exposed to Infrared radiation the bond between two atoms would absorb energy. What makes IR unique for different bonds is that depending on which two atoms are in a bond the energy absorbed would be different. For example C-H bond compared to C-O bond. Hydrogen is lighter than Oxygen in its atomic mass therefore vibrates more.

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