NMR
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what type of solvent is CCl4?
non-polar compound so good solvent for non-polar organic molecules with no H atoms
what type of solvent is CDCl3?
is a polar covalent molecule so good solvent for polar organic molecules with no H atoms
why is TMS used?
• to calibrate the spectrum • only gives one signal, • its signal is away from all other signals, • gives a strong signal so only a small amount needed, • non-toxic, • inert, • low boiling point so can be removed easily from sample
splitting of peak equals ?
Splitting of peak = number of inequivalent H’s on neighbouring C atoms + 1
hydrogens bonded to a oxygen or nitrogen?
A hydrogen bonded to a nitrogen or an oxygen usually do not couple with other protons and appear as singlets on the 1H NMR spectra.
how do elements posses spin ?
Nuclei of elements with an odd mass number possess spin
TMS name?
tetramethylsilane
on a C NMR what does the number of signals mean ?
No. of C environments
on a C NMR what does the position of signals mean?
chemical environment of C’s
in H NMR what does the number of signals mean?
No. of H environments
in H NMR what does the position of the signals mean?
chemical environment of H’s
in H NMR what does the intensity of the signals mean?
the relative number of H’s causing the signal
what is the difference between high resolution and low resolution NMR H1?
In a HIGH RESOLUTION spectrum each signal is split into a more complex pattern
what does splitting mean in H1 NMR?
The splitting pattern depends on the number of chemically different H’s on adjacent atoms. It happens because the spins of adjacent H’s interact with each other in a process called ‘spin-spin coupling’
number of hydrogen atoms present?
In 1H nmr (but NOT 13C) the area under a signal is proportional to the number of hydrogen atoms present