Answer 6.2

a) Explain the nitrogen rule.

If a compound contains an even number of nitrogen atoms (0, 2, 4, …), its monoisotopic molecular ion will be detected at an even-numbered m/z (integer value).
Vice versa, an odd number of nitrogens (1, 3, 5, …) is indicated by an odd-numbered m/z.

b) Apply the nitrogen rule to the compounds below. Do not calculate molecular weights. Simply fill “even” or “odd” into the second column!

c) Consider a radical containing no nitrogen to be cleaved off from an even-mass molecular ion. Will the mass of the fragment be even- or odd-numbered?

The m/z value of the fragment will be odd-numbered.

d) Consider a molecule containing one nitrogen to be eliminated from a molecular ion containing two nitrogens. Will the mass of the fragment be even or odd-numbered?

The m/z value of the fragment will be odd-numbered.