Steven Matthews - NMR Flashcards
What are the main applications/uses of NMR?

What is Nuclear Spin?

For a spin ½ nucleus, what happens when we place the nuclear magnetic field into external magnetic field?

What does the energy level between these two states depend on? Can we manipulate the number of nuclei in these two states?

Is NMR as sensitive as other techniques that use higher magnetic fields ?
NMR is not as sensitive as other techniques that use higher magnetic fields
Because we are dealing with very small energy differences between spin states.
Example - The energy differences are 10-5 smaller than that associated with infrared.
Examples of frequently used spin nuclei, spin state and their relative sensitivity?
Proton has largest γ as it has the smallest nucleus

In the past how were NMR spectra recorded?

What does the Larmor precession of nuclear spins refer to?

How can we represent the net magnetisation of spin 1/2 nuclei in the presence of strong external magnetic field?

What happens to the net magnetization when we apply a radiofrequency pulse?

Describe what happens to the spin states in the images when a radiofrequency pulse is applied at 90o?


What is the relationship between the length of a frequency pulse and the number of frequencies it contains?

Outline the basic principle behind NMR?
Hint - Pulse, free induction decay and Fourier transform

What are the different parameters on an NMR spectra?

What is meant by the term chemical shift?

What scale is used to measure the chemical shift?

When do we get chemical shift equivalence? When is the chemical shift for a proton the same?

What are the chemical shift ranges, what type of functional groups do we find to the left (downfield) and right (upfield) on the chemical shift spectrum?
Think of it as electron density
Left (downfield) - Low electron density around nucleus - Presence of electron withdrawing group
Right (upfield) - high electron density around nucleus

What the hell can we actually use chemical shifts for?

What do we use integrals for/relative height of the peak? What happens to the integrals when the NMR reflects a mixture of molecules?

In NMR, what does coupling refer to?

What is scalar coupling?
Example - Two spin system?

What are the different possible scalar coupling patterns? What can they be used for?

Typical scalar coupling values?

Coupling constant (J) - Hz
Indicate the degree of splitting that is found between these interactions - to what extent the peaks split




































