organic analysis Flashcards
what does NMR give information about
position of the 13C or 1H atoms in a molecule that resonates the different frequencies
what does the number of peak in 13C NMR represent
the number of carbon environments in a molecule
what does the numbers of peaks in 1H nmr spectra represent
each peak in a 1h nor spectra has an integration trace which chooses the relative number of 1h in each environment
what does high resolution 1h have the ability to show
spin-spin coupling, this is useful because spin spin coupling causes splitting pattens which give information about neighbouring hydrogen atoms, the splitting pattern is determined by N+1 rule
what is n+1 rule
if there are no hydrogen atom attached to the carbon atoms adjacent to a 1H environment, the the peak reprinting that environment will be spilt into n+1 peaks
what is chemical shift
it depends on the molecular environment, it relates to the difference in frequency between a chemical environment and TMS
what is integrated spectra
indicates the relative number of the 1H atom in different environments
how is 1H Nmr spectra obtained
using samples disabled in deuterated solvents or CCL4
what is tertramethylsaline
TMS as a standard used to measure an NMR spectrum peak against it, the 4 methyl groups are in the same chemical environment and produce an intense signal
what is a denatured solvent
any H atoms are replaced with deuterium so have no overall effect of the spectra
what is chromatography used for
used to spectate and identify the components in a mixture
what is the mobile phase
substance in chromatography that carries the soluble components of the mixture
what is the stationary phase
substance in chromatography that holds back components that are attracted to oy
how are components separated
each components in the mixture has a different level of solubility in the mobile phase and retention in the stationary phase
what is thin layer chromatography
a plate is coated with a solid and a solvent moves up the plate column, an organic solvent is used as the mobile phase. A sheet coated with a thin layer of silica gel acts as the stationary phase. Thin layers can be used to separate and identify amino acids by their rf values.
how are amino acids separated by thin layer chromatography
different amino acids have different r groups, so they have different affinities for the solvent therefore will move up the plate at different rates depending on their affinity
why do we add a visible developing agent
amino acids are colourless
what is column chromatography
a column is packed with a solid and a solvent moved down the column, silica is packed in a narrow column and cats as a stationary phase, the mixture if dissolved in a solvent and poured through the column this acts as a mobile phase
what is gas chromatography
a column is packed with a solid or with a solid coated by a liquid and a gas is passed through the column under pressure at high temperature, the stationary phase is a solid or liquid coating inside a long coiled tube, an inert has e.g. N2 is produced.
what is retention time
the time taken for a component to leave the coil is the retention time, this can be compared with standards to identify substances.
what is a chromatograph
shows the retention times as a series of peaks with the are under each peak being proportional to the amount of components present
what does separation depend on
the balance between solubility in the moving phase and retention by the stationary phase
how to identify different substances
by the retention time and rf values
what is mass spectrometry used for
analyse the components separated by gas chromatography, the mass spectrum of each component can be compared to spectra in a database, allowing components to be identified with greater certainty
