Triphenylphosphine (TPP) derivatives, which are catalysts of reactions with epoxy and phenol compounds, were investigated regarding the melting behavior and catalyst effect. The melting behavior was measured by differential scanning calorimetry (DSC), and the relationship of melting behavior (melting point and heat of fusion) and chemical structure were discussed using the heat of formation calculated by a semiempirical method. Two schemes are proposed for the reactions with epoxy and phenol compounds: a complex formation scheme, and an ionic scheme. The ionic scheme was the predominant route in the reactions with epoxy and phenol compounds in the bulk state at high temperature (180degreesC) on the basis of DSC measurements of the curing reaction and the semiempirical calculation of the heat of formation of products and partial charge of the phosphine group in the TPP derivatives. Consequently, the reaction rate of epoxy and phenol compounds decreased by introducing electron-withdrawing substituents such as chlorine in the basic catalyst.