PL - Combined techniques Flashcards
How can different spectra’s/techniques be used to deduce a molecules structure?
The mass spectrum will tell you the relative mass of the molecule and shows which (functional) groups it is likely to contain - e.g. CH3.
The IR spectrum suggests what bonds are present and therefore gives an idea of what type of molecule it is - e.g. an aldehyde, ketone, ester, carboxylic acid etc. It also cancels out some of the molecule types.
The high resolution proton NMR spectrum shows how many hydrogen nuclei are in how many environments. Also, using the information from the spectra above, it can further suggest what groups each chemical shift is due to/caused by. The area under the peaks can also be used to confirm this by telling you how many hydrogen atoms are in the groups. The splitting pattern might show that the protons are on adjacent carbon atoms, further suggesting a group present.
The carbon-13 NMR spectrum shows the number of carbon nuclei in the number of different carbon environments. It also shows what groups the chemical shift values are due to.
All of this can be put together to give the structure of the molecule.
Apart from spectra, what can also be used to help work out a structure?
Elemental analysis.
How can elemental analysis also help to work out a structure?
1) In elemental analysis, experiments determine the masses or percentage compositions of different elements in a compound.
2) This data can help you work out the empirical and molecular formulae of a compound.
3) Knowing the molecular formula is useful in working out the structure of the compound from different spectra.
In elemental analysis, what do experiments determine?
The masses or percentage compositions of different elements in a compound.
What can the data obtained from elemental analysis whereby experiments determine the masses or percentage compositions of different elements in a compound help us to work out?
The empirical and molecular formulae of a compound.
What is knowing the molecular formula of a compound useful in working out?
The structure of the compound from different spectra.
What can you work out from different spectra if you know the molecular formula of a compound?
The structure of the compound.
Which type of spectrum gives you the mass of a molecule?
Mass spectrum.
Which spectrum can tell you how many carbon environments are in a molecule?
Carbon-13 NMR spectrum.
Which spectrum can tell you how many different hydrogen environments there are in a molecule?
The high resolution proton NMR spectrum (the 1H NMR spectrum).
What information can you find from elemental analysis?
The masses or percentage compositions of different elements in a compound.
This data can then be used to help you work out the empirical and molecular formulae of a compound which can then be used alongside other information to work out the structure of the compound from different spectra.
