Experimental Determining Structure Flashcards
what experimental techniques are used to verifiy the chemical structure of a substance in organic chemistry?
elemental microanalysis
mass spectroscopy
infrared spectroscopy
proton NMR spectroscopy
what is elemental microanalysis used for?
it determines the masses of C, H, O, S and N in a sample to calculate the empirical formula
what happens to the compound in order to carry out elemental microanalysis?
the compound is destroyed during the process
what is mass spectroscopy used for?
determines the GFM of a compound
provides information about the structure of the molecule
how does mass spectroscopy work?
a sample is bombarded with high-energy electrons
this produces positively charged molecular ions (parent ions)
the ion fragments are detected based on their mass to charge ratio (m/z)
what information does the mass/charge (m/z) ratio provide?
it gives the GFM and helps determine the molecular formula
what happens to the compound in order to carry out mass spectroscopy?
the compound is destroyed during the process
what is infrared (IR) spectrscopy used for?
it identifies functional groups and bonds in organic compounds
how does infrared (IR) spectroscopy work?
IR radiation causes bonds to vibrate (stretch and bend)
the wavelengths absorbed depend on the type and strength of the bonds
what is absorbance measured in?
wavenumbers (cm-1)
what is proton NMR (1H NMR) used for?
it gives information about the chemical environments of hydrogen atoms (protons) in an organic molecule
how does proton NMR work?
hydrogen nuceli drop to align with the strong magnetic field and a dfifferent wavelength is emitted for different hydrogen environments present
what does the chemical shift (δ) in an NMR spectrum indicate?
the position of the peak reflects the environment of the hydrogen atom and is measured in ppm
what does the area under the NMR peak respresent?
the number of H atoms in that environment (shown as a ratio)
what is the standard reference substance used in proton NMR?
tetramethylsilane (TMS)
it is assigned a chemical shift of 0 ppm
what does high-resolution NMR provide?
a more detailed spectrum showing multiplets due to splitting of peaks
what causes splitting in high-resolution NMR?
interaction with hydrogen atoms on neighbouring carbons
what is the n + 1 rule in NMR spectroscopy?
if n hydrogen atoms are on a neighbouring carbon, the peak will split into n + 1 peaks
