Proton NMR Flashcards
Similarities between proton NMR and carbon 13 NMR
One signal for each set of equivalent H or C13 atoms
The closer the atom to a very electronegative atom and/or double bond the greater the chemical shift (to the left)
Differences between proton NMR and carbon 13 NMR
Proton NMR has a relative area of signals related to relative number of H atoms whereas carbon has no link
In proton the signal is split by neighbouring H atoms on adjacent carbons whereas carbon 13 has no splitting
Name of molecule you wish to prepare
Target molecule
steps to prepare to run a proton NMR spectrum`
sample dissolved in solvent
placed in long narrow tube
what does a spectrum proton NMR machine use to find the peaks
uses radio waves
in a very strong magnetic field
using superconductive magnets
structures in a proton NMR machine
magnet
nitrogen jacket
probe
helium jacket
what does a proton NMR test for in certain atoms
nuclear spin
some examples of molecules with nuclear spin
13C and 1H
what does a nuclear spin generate
a magnetic field
what does the direction of a magnetic field depend on in an atom
the direction of spin
does the direction of spin usually have the same or different amount of energy
the same
why do different directions of nuclear spin have different energies in a magnetic field
one way is opposing the magnetic field
what is the difference in nuclear spin (the energy gap) corresponded to
the frequency of radio waves
solvent used for proton NMR
CCL4
CDCL3
why are these solvent used for proton NMR
free of H atoms
what is the chemical used to calibrate the proton NMR spectrum
tetramethylsilane
TMS
why is TMS used to calibrate proton NMR
its signal is far away from other signals
it only gives one signal
its non-toxic
it is inert
it has a low boiling point so easily removed
how many signals for each equivalent set of H atoms it represents in proton NMR
1
what is the intensity of each signal proportional to
the number of equivalent H atoms it represents
what does the area of a HNMR peak represent
the same area represents the same overall number of H atoms
equation for spin-spin coupling in HNMR
number of H’s next door + 1
name of spin-spin coupling with one peak
singlet
name of spin-spin coupling with two peaks
doublet
name of spin-spin coupling with three peaks
triplet
name of spin-spin coupling with four peaks
quartet
name of spin-spin coupling with multiple peaks
multiplet
exceptions to spin-spin coupling in HNMR
H’s that are equivalent
H’s that are on O’s
what is the spectra recorded on the scale of HNMR
chemical shift
what does the chemical shift mean in proton NMR
how much the field is shifted compared to the field of TMS
equation for finding the chemical shift of a peak in HNMR
((field for TMS - field measured) / field for TMS) X 10^6
units for chemical shift HNMR
parts per million
what changes the chemical shift of a peak
the more electronegative groups around the H the greater the shift
what would triplet quartet in ratio 3:2 mean
CH3 - CH2 ethyl group
what would triplet triplet in the ratio 2:2 mean
CH2 - CH2
what would a singlet at intensity 3 mean
CH3 - methyl group
what would a singlet at intensity 1 mean
OH - alcohol group
