Question

What are the important concepts of 1H Nuclear Magnetic Resonance Spectroscopy? How to determine which Hydrogen connected to a Carbon is which peak?

Answer 1

The important concepts of 1H NMR spectroscopy or proton magnetic resonance spectroscopy is confind to hydrogen nuclei or proton since they are present in almost all organic compounds.

a) In the absence of an external magnetic field,the nuclear magnets spin at random in their atomic but when placed in a strong,uniform external magnetic field.

b) In the lower energy state, the fields are aligned with each other (parallel) whereas in the higher energy state, the fields are alligned against each other (antiparallel). The parallel orientation is generally more stable by a small amount of energy.

c) When a proton in an organic molecule is placed in a strong magnetic field,it can align with the field or against it. In the more stable low-energy state, it is aligned with the magnetic field.

d) The energy requird to flip the proton is not much and depends on the strength of the field.

e) If energy is supplied in the form of radiowaves of exactly the right frequency, radiation will be absorbed and the nucleus will flip and align against the applied magnetic field in the higher energy state.

The number of peaks into which a particular proton's signal is split,is equal to one more than the total number of protons on directly adjacent carbons. If a proton has 'n' number of neighbouring non-equivalent protons,its signal is split into (n+1) peaks. The number of peaaks into which a particular signal s split is called its multiplicity.

So hydrogen connected to a carbon is (n+1 ) peak.