Page 37 - Practical-organic-3

❖ NMR theory depends on spinning of nucleus (+ve) that has odd mass number such
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as: ( H, C, N, F, P) around their axes.
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❖ When charged particles such as H or C spin on their axes, they create magnetic field.
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❖ There are two magnetic fields that affect the spinning of nucleus:
1. External magnetic field (related to the NMR spectroscopy).

2. Induced magnetic field (related to the electrons of the atom).

❖ NMR spectrum is a plot of the intensity of a peak against its chemical shift, measured in

parts per million (ppm).

❖ Features of NMR spectrum:

1. No. of signals (peaks): indicate how many different sets of protons.
▪ Equivalent atoms: have the same chemical environment & appears in one signal

▪ Non-equivalent atoms: have different chemical environment & doesn’t appear in one

signal

2. Chemical shift: give information about the electron density around each set of atoms.

▪ Shielding (up field): atom with  electron density & appears at lower
frequency.

▪ De-shielding (down field): atom with  electron density & appears at higher

frequency.

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