Definition of Fragmentation

(1) The heterolytic cleavage of a molecule according to the general reaction

a-b-c-d-X (a-b)+ + c=d + X-

where a-b is an electrofuge and X is a nucleofuge (which may emerge from the reaction in combined form), and the middle group affords the unsaturated fragment c=d. For example,

Ph3C-CO2H + H+ Ph3C+ + C=O + H2O

GROB (1969).

(2) The breakdown of a radical into a diamagnetic molecule or ion and a smaller radical, e.g.,

(CH3)3C-O. (CH3)2C=O + H3C.

[ArBr]. - Ar. + Br- (solution)

(3) The breakdown of a radical ion in a mass spectrometer or in solution, forming an ion of lower molar mass and a radical, e.g.,

[(CH3)3C-OH].+ (CH3)2C=OH+ + H3C. (mass spectrometer)