Spectroscopy
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What is mass spectra used for?
Identifying the molecular mass of a compound Gaining further information about a compounds structure
What happens when an organic compound is placed in a mass spectrometer?
Loses an electron and forms a positive ion
What is the molecular ion?
The positive ion when a molecule loses an electron
Where is the molecular ion peak located?
A clear peak at the highest m/z value on the far right hand side of mass spectrum
Why do some molecules have a small peak after the molecular ion?
They have a small proportion of carbon-13 present in the molecule
What are fragment ions?
Peaks in mass spectrum formed from the break down of the molecular ion
What two species does simple fragmentation break a molecule into?
A positive ion and a radical
What does absorbing IR do to covalent bonds?
Makes them stretch and bend more
Why do molecules stretch?
To increase the distance between the atomic centres
What 2 factors affect how much a bond stretches or bends?
Mass of the atoms in the bond Strength of the bond between atoms
What is the only radiation a bond can absorb?
Radiation that has the same frequency as the natural frequency of the bond
Explain how the ‘Greenhouse Effect’ works?
Sun’s visible light and IR radiation passes into the Earth’s atmosphere Earth absorbs radiation Some radiation re-emitted in the form of IR Greenhouse gases(GG) absorb this radiation as same frequency as there natural bonds Vibrating bonds in GG’s re-emit radiation that heats up atmosphere
What are the 3 most common greenhouse gases?
Water Vapour, Carbon Dioxide, Methane
Explain the 4 steps of how IR spectroscopy works
1) Sample placed in IR spectrum 2) A beam of IR radiation in range 200-4000 is passed through sample 3) Some radiation absorbed and emerging beam of radiation identified what has been absorbed 4) Graph of transmittance against wave number produced
Where does the finger print region occur?
Below 1500cm^3
What is the finger print region and how is it used?
An area in which the exact molecule can be determined due to unique peaks Uses computer software or comparing booklets to published spectra
What are two key applications of mass spectrometry?
Breathalysers Break down of pollutants present in the atmosphere
What are 3 processes used in molecule identification?
Elemental Analysis Mass Spectrometry IR spectroscopy