Infrared Spectroscopy

• • Covalent bonds within molecules absorb energy within the infrared region of the electromagnetic spectrum that has the same vibration frequency ---> causes bonds to vibrate more ---> which causes a stretching or bending motion.
• Factors that affect the amount of vibration in abroad:

  • Bond strength
  • Bond Length
  • Mass of each atom in the bond
• • 1 / wave length = wavenumber (cm-1)
  • Higher wavenumber ---> smaller wavelength----> higher energy wavelengths absorbed.
  • Therefore the wavenumber is proportional to energy
• • The fingerprint region is a section of the IR spectrum from 500 - 1000 cm-1. This region produces a pattern unique to each different molecules.
• Uses of infrared spectroscopy:

  Breathalyser tests - The intensity of ethanol's C-H peak indicates how much present in a person's breath. <--- indicates if they are overt the legal alcohol limit.

  Atmospheric monitoring - Peak intensity for gases like CO and NO show pollutant levels in the atmosphere from car emission and industrial processes.