22.2.4—Suggest the identity of molecules formed

Fragment ions form when a molecular ion breaks into smaller charged pieces. A proposed fragment must have a plausible formula, m/e value and neutral partner that together reconstruct the parent.

Use common stable cations and the molecular structure as constraints. Fragment abundance reflects stability and pathway, not simply the number of atoms.

A peak at m/e 29 may be C₂H₅⁺. Pairing it with a neutral radical or molecule must preserve the parent formula and electron/charge accounting.

Any formula matching a mass is not automatically the fragment identity; check connectivity and complementary loss.