C17 - Spectroscopy Flashcards
What is fragmentation?
The process in mass spectrometry that causes a positive ion to split into smaller pieces, one of which is a positive fragment ion.
What are fragment ions?
Ions formed from the breakdown of the molecular ion in a mass spectrometer.
What is Carbocation?
An ion that contain a positively charged carbon atom.
Example of a tertiary carbocation?
H3C
|
H3C — C+
|
H3C
What is the isotope split for Flourine, Bromine and Chlorine that you will see in the mass spectrum?
Fluorine only one line.
Bromine has 50/50 isotope ration (two line same length)
Chlorine has a 1 to 3 isotope ration (two lines)
How does a mass spectrometer work?
A
How do you find the relative molecular mass of a compound using a mass spectra?
The second last peak is the molecular mass as there is a smaller peak to the right, the M+1 peak assuming that the ion has a +1 charge, which it normally will have.
How can you find out the structure of a molecule by the mass spectra?
Work out what ion has made each peak at the M/Z value.
What are some common fragments?
CH3+ = 15 m/z
C2H5+ = 29 m/z
OH+ = 17 m/z
How do you combine techniques to identify a compound?
- Mass or percentage composition to work out the molecular formula of the compound.
- Work out what functional groups are in the compound from its Infrared spectrum.
- Use the mass spectrum to work out the structure of the molecule.
How does Infrared radiation work?
A beam of IR radiation is passed through a sample of a chemical. The IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy. Bonds between different atoms absorb different frequencies of IR radiation.
What are the two ways Infrared Radiation is used in the real world?
- Modern breathalysers to measure the amount of ethanol vapour in the breath.
- Monitor gases causing air pollution by the concentrations of polluting gases in the atmosphere, carbon monoxide (CO) and nitrogen oxide (NO) from car emissions.
