4.2.4 analytical techniques
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what is infrared spectroscopy and how is it used
• measures certain bonds in a molecule absorbing infrared radiation at characteristic frequencies that cause covalent bonds to vibrate • a computer then compares IR spectra to a database to identify the compound
what is the greenhouse effect
• CO2, methane and water vapour are greenhouse gases and they trap the Earth’s radiated IR energy in the atmosphere • the IR radiation is absorbed by C=O, O-H and C-H bonds which then contribute to global warming
what contribution does CO2 have to global warming
• concentrations of CO2 in the atmosphere have risen significantly due to increased burning of fossil fuels • the greenhouse effect id dependent on the amount of CO2 in the atmosphere, its ability to absorb IR and how long it stays in the atmosphere
how can infrared spectroscopy be used practically
• to monitor gases causing air pollution - modern breathalysers to measure levels of ethanol in the breath
what is the process of mass spectrometry
• when a molecule is put through a mass spectrometer it will break up to give a series of peaks caused by fragments • the peak with the largest m/z is equal to the Mr and is called the molecular ion peak
what is fragmentation
• the molecular ion fragments due to covalent bonds breaking - more stables ions like carbocations will cause a greater peak intensity