Effect of overcrowding in mass spectra for six violanthrenes

The mass spectra of six highly purified violanthrene samples of class A—(benzo[ rst ]anthro[10,1,2‐ cde ]pentaphen, benzo[ rst ]phenanthro[10,1,2‐ cde ]pentaphene), class B—(benzo[ rst ]phenanthro[1,10,9‐ cde ]pentaphene, dibenzo[ a,rst ]naphtho[8,1,2‐ cde ]pentaphene) and class T—(tetrabenzo[ a,cd,j,lm ]perylene, tetrabenzo[ de,hi,op,st ]pentacene) were measured. The dependence of relative ion instensities for monovalent, divalent and trivalent ions [M] i + , [M – 2 n ] i + and [M – 15] i + ( i = 1, 2, 3) showed clearly the effect of overcrowding in condensed aromatic rings, i.e. the number of H 2 molecules which are readily eliminated from the molecular ions is zero for class A, one for class B, and two for class T. These numbers are the same as the number of overcrowded hydrogen atom pairs for each class.