The electron impact mass spectra of a series of o-hydroxyphenyl dialkyl phosphine oxides (1) and dialkyl o-hydroxyphenylphosphonates (2) were investigated. The principal fragmentation pathways are the cleavage of P-Cw3 bond, the McLafferty rearrangement involving p=O group and the mixed process of these two pathways for o-hydroxyphenyl dialkyl phosphine oxides, but for dialkyl o-hydroxyphenylphosphonates, the successive McLafferty rearrangements are observed to be the predominant one without the cleavage of P-Csp2 bond which occurs as a minor process in the fragmentation of compound 1.

The electronic structures of 17 perchlorofiuoroolefins and perfluoroolefins were calculated using the MNDO method. Based on these calculations combined with the perturbation theory, a good structure‐reactivity relationship of perchlorofluoroolefins has been established. In the case of internal olefins, the direction of nucleophilic attack is governed not only by the perturbation energy of the ground state, but also by the stability of the anionic intermediate and the activation energy of the reaction.

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