What's in a medicine- IR Spectroscopy


What are the main steps of IR spectroscopy?

1. exposing the bonds between molecules to the infra-red radiation. Bonds will absorb specific frequencies of IR radiation depending on the strength and length of the bond

2. An IR spectrometer will then detect any absorptions, and so will produce an infra-red spectrum in accordance to the molecule

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What is bond-stretching and where does it occur?

- bond stretching usually occurs within simple diatomic molecules, which can only vibrate one way (this is by the atoms in the bond pulling and pushing). This results in there usually only being one vibrational infrared absorption as a result- which correpsonds to the molecules changing energy levels 

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Other vibration modes:

- rocking and twisting- this occurs as molecules will have bonds with different bond enthalpies, meaning different frequencies of radiation will cause them to do different things

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How are troughs caused?

when energy is being absorbed from that particular frequency of infra-red to excite the bonds, and cause them to move into a higher state of vibration/ energy level 

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What is the fingerprint region?

the region that is characteristic of a particular molecule

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Why should you ignore the absorption range of 1500

because it can become very complex, and as a result difficult to assign absorptions to a particular bond

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How can you find the wavenumber?

divide 1 by the wavelength of the IR radiation, which can be found by dividing the wavespeed (3x10^8) by the frequency that has been absorbed by that bond 

however, as the speed of light is constant, it becomes easier to do 1/wavelength 

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