Ortho-rearrangement in the mass spectra of diphenylmethanes

The mass spectra of all possible methyl substituted derivatives of 3,3′,5,5′-tetramethyl-4, 4′-dihydroxy-diphenylmethane are recorded. The direct influence of steric hindrance to free rotation about the aryl-methylene bonds results in the progressive importance of ortho-rearrangement in the ionization-dissociation pathways of these compounds.