Question

How do we know the intensity ratio of multiplets in the `""^1H` `NMR` spectrum?

Answer 1

Pascal's triangle gives the relative intensity of multiplets.........

Explanation:

....the pattern of peak intensities measured by integration follows `"Pascal's triangle..........."`

A singlet has relative intensity `1`.....

A doublet has relative intensity `1:1`.....

A triplet has relative intensity `1:2:1`.....

A quartet has relative intensity `1:3:3:1`.....

And a quintet has relative intensity `1:4:6:4:1`.....

Notice the relationship between the triangle and the relative intensities?

Even with the best, highest field spectrometers, quintets, and hextets, and higher multiplets may TEND to overlap and lose resolution. The inset shows the methine absorption for `(H_3C)_2CHI`; this is a septet with relative intensity, `1:6:15:20:15:6:1`.....