IR Spec

• What happens when covalent bonds absorb infrared radiation?

  they begin to vibrate
• What are the two actions that occur when the Bond vibrates?


  It either begins to stretch in a rhythmic movement along the line, or it begins to bend which results in a change in bond angle
• What does the amount a bond stretches or bends depend on?


  the mass of the atoms in the bond, heavier atoms vibrate more than lighter atoms

  the strength of the bond, stronger bonds vibrate faster than weaker bonds
• What is the range of wavelengths in the IR?

  200cm-1 -> 4000cm-1
• What are the steps of Ir spec?

  The sample is put through an IR spectrometer

  A beam of IR radiation with the range of 200-4000cm-1 is passed through the sample

  The molecule absorbs some wavelengths and the emerging analysis is presented on a graph

  The peaks can then be used to identify specific functional groups
• What is the fingerprint region in IR spec?

  1500-400 cm^-1
• What is the fingerprint region used for?


  Identifying specific molecules, it is used specifically by the computer as it compares the fingerprint region of many samples meaning it can be used as a benchmark for comparing compounds
• What are some applications of IR spectroscopy?

  Identifying pollutants from cars, it measures hydrocarbon carbon monoxide and dioxide levels too.
• What is the applications of IR spectroscopy for police?

  It is used in breathalysers, the normal characteristics are of ethanol are then investigated, the more IR absorbed the higher the reading, the more ethanol in your breathe
• What is the typical sequence for identification of a compound?


  Elemental analysis- using percentage analysis of compounds to identify empirical formula

  Mass Spectrometry- use of the molecular ion peaks from mass spectrum to determine the Mr, use of fragment ions to identify sections of a molecule

  Infrared Spectrometry- Use of absorption peaks from an IR spec to identify functional groups that are present in molecules