Experimental Determination of Structure Flashcards
How to do empirical formula questions
Write table with element, mass, gfm, moles, ratio and empirical formula.
Work through.
How mass spectrometry works
Molecule is bombarded with electrons, this will split the molecule into positively charged ion fragments. These are then accelerated into a magnetic field, the smaller the mass to charge ratio the greater the deflection. Each ion path is record hence the mass of each can be determined.
How to read mass spectrometry spectrum.
Farthest away from origin will be GFM we can combine this with empirical formula to find out more about molecule. Other fragments can tell us more about the groups within.
How infrared spectroscopy works
When infrared radiation is absorbed by bonds within a molecule they will vibrate but bond won’t break. Wavelength absorbed by bond depend on surrounding atoms. The spectrum of wavelengths absorbed can be recorded and expressed on a graph.
Where are peaks on infrared spectroscopy.
Peaks are the troughs on a typical graph.
What is the absorbed wavelength expressed in
Wave number
Wave number =
1/wavelength
How does proton NMR work
Proton can spin in two directions, when in magnetic field one will align with it the other aligns against it. The one aligned with it will have less energy than that aligned against it. Due to this energy gap, when hit with radiation the lower proton energy will be promoted to higher energy. It will then drop down releasing the radiation is absorbed. This radiation can be measured. Specific Hydrogen environments have specific energy gaps so specific radiation released
2 types of proton NMR
High resolution and low resolution
What is area under graph of a low resolution proton NMR proportional to?
Number of protons of that environment.
What is different about low resolution proton NMR and high resolution proton NMR
High resolution has multiplets.
What is a multiplet
Multiple peaks close to one another
What does number of multiplets tell us
N peaks= N-1 neighbouring hydrogen environments
