NMR Preview Flashcards
what does NMR tell us
it tells us how the carbon and hydrogen atoms are connected to eachother
when a proton rotates, what does it create?
it creates an electric field that allows it to act like a magnet
when a proton is subjected to an external magnetic field (B0) what can happen to the magnetic moment?
it can align either with the external field (⍺ spin state, lower in energy) or against the external field (β spin state, higher energy)
what is nuclear resonance?
when an proton flips from one spin state to another, it is said to be in resonance
what does the electron density around a proton create?
it creates an induced magnetic field that points in the opposite direction of the external magnetic field, this makes the net field that the proton experiences smaller
When a proton is deshielded, what happens to the chemical shift
the proton experiences a larger magnetic field and has a larger energy gap between the spin states, this causes it to have a higher chemical shift
what is the shielding affect on a proton
a proton is shielded by its surrounding electron density, the shielding lowers the experienced magnetic field by the proton and causes it to have a lower chemical shift
when are the two protons on an CH2 carbon chemically equivalent? When are they not?
the protons are chemically equivalent when there is no chiral center, when theres a chiral center, the two protons are no longer chemically equivalent
when are CH3 protons chemically equivalent
always, even on chiral centers
what is the left side of the NMR spectrum called
downfield (deshielded protons, higher experienced magnetic field)
what is the right side of the NMR spectrum called
upfield (shielded protons, lower experienced magnetic field)
what happens to the chemical shift if you have a more electronegative atom on a molecule
the electronegative atom will pull electron density away from the proton and deshield it, this results in a higher chemical shift
how do you use integration
divide all the integration values by the lowest value and multiply each by 2, this should account for the number of protons present
what is spiltting
it is the effecr caused by the magnetic fields of the neighboring protons
what is the n+1 rule
it allows us to predict the number of peaks we would expect in a compound given the number of neigbors
