NMR Revision Flashcards
What does a nucleus possess (relevant to NMR)?
Magnetic moment
What does a magnetic moment have?
Spin quantum number, I
I is non-zero
What happens when an external magnetic field is applied?
A number of orientations are allowed
Possible orientations = (2I+1)
Transitions where a change of Δm = +/-1occur are allowed
Splitting of degenerate energy levels
What are the magnetic states in abscence of a magnetic field?
Magnetic states will be degenerate (same energy)
What are the spin quantum numbers of 1H, 13C, 19F and 31P (normal spin quantum number)?
Nuceli have spin quantum number I=1/2
What happens if nuclei with spin quantum number of 1/2 are placed in a magentic field?
2 spin states occur
m = +1/2 or m = -1/2
Explain the 1/2 spin nuclei diagram and what direction nuclei spin at higher and lower energies.
What is B0 in comparasion to Beff?
B0 = Magenetic field
Beff = Effective magnetic field (actual magetic field experienced)
Why does Beff have a different magentic field?
The motion of electrons surrounding the nucleus will result in induced magnetic fields - shielding
What is the Beff equation?
Beff = B0(1 – σ)
Recall and write down the chemical shift diagram
How to convert chemical shift (ppm) to frequency (Hz)?
δ = 10^6 x (Δv / spectrometer frequency)
What is coupling?
When a small magnetic field arising form one nucleus influences the magnetic field experienced by the other non-equivalent nuclei that is nearby in the molecule
What are the other 100% abundant nuceli with spin 1/2 and what are some fallbacks?
Sensitivity can vary hugley. 13C ideal.
89Y also only tells you that you have Y in your complex.
What equation predicts coupling splitting patterns?
2nI + 1
n = number of coupling nuclei possessing a magnetic quantum number I
I = spin of the quantum number
(For 1/2 spin nuclei - simplifies to n+1)
