Instrumental analysis Flashcards
How can you use a mass spectrometer to identify an organic compound?
The peak with the largest mass/charge ratio is the molecular ion and gives the Mr of the compound.
How do you know if chlorine or bromine is present in an organic compound using a mass spectrometer?
Two peaks for the Mr will be seen as these halogens can exist as two isotopes.
What is the molecular ion?
The positive ion formed in a mass spectrometer from the whole molecule.
What is fragmentation?
The splitting of molecules in a mass spectrometer into smaller parts.
How can you use infrared spectroscopy to identify an organic compound?
The wave number at which absorption occurs is characteristic of the bond and therefore useful in identifying the functional groups present (troughs).
What is the wave number?
A measure of energy absorbed, used in the IR spectra.
What is the characteristic absorption?
The wave number range at which a particular bond absorbs radiation.
How can you use NMR to identify an organic compound?
The energy absorbed depends on the environment in which the atom is. Each absorption will appear at a different place on the spectrum and the chemical shift for the peak tells you the energy involved.
What are the two types of NMR spectra?
13C and 1H.
What is the chemical shift?
A measure of difference in parts/millions from the standard of the energy of a particular absorption type.
What is the environment?
The nature of the surrounding atoms/groups in a molecule.
How does a 13C spectroscopy work?
The presence of very small amounts of 13C in organic compounds means that they will absorb energy and produce a spectrum.
How can you use 13C spectroscopy to identify an organic compound?
The number of peaks gives the number of different carbon environments.
The chemical shifts of the peaks gives the type of carbon environment.
How can you use 1H spectroscopy to identify an organic compound?
The number of peaks gives the number of different proton environments.
The chemical shifts gives the type of proton environment.
The heights of the peaks give the ratio of the number of protons in each environments.
What is the other name for 1H spectroscopy?
Proton spectroscopy.
