Exothermic thermal reaction of dopamine with 3,5‐dinitrobenzoic acid

Abstract

AbstractPyrolysis of the crystalline 1 : 1 molecular complex DAċdnba, which was prepared from cocrystallization of dopamine (DA) and 3,5‐dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting‐point, leading to the formation of a black solid along with a tiny amount of 3‐amino‐5‐nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DAċdnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PAċdnba (PA: β‐phenylethylamine), BAċdnba (BA: benzylamine), DMDAċdnba (DMDA: O,O′‐dimethyldopamine) and DHBAċdnba (DHBA: 3,4‐dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DAċdnba. Copyright © 2003 John Wiley & Sons, Ltd.