engleski

In-situ Powder X-Ray Diffraction monitoring of the thermochromic imines syntheses

Imines (Schiff bases) are a long time known group of photochromic and thermochromic organic compounds. To obtain a better insight into their chromic properties, ortho-hydroxy aromatic Schiff bases have been synthesized by neat grinding (NG) in an agate mortar in few minutes. The thermochromic properties were studied using SCXRD giving quantitative insight into the diverse colorization upon intramolecular proton transfer changes, tautomer equilibriums and molecular planarity. The mechanochemical methods of synthesis of organic compounds are being under investigation for cca. 20 years now. During the past decade it has been reported that the solvent-free synthesis and mechanochemistry are effective methods of efficient and time-saving synthesis of imines. Nevertheless the studies of the reaction mechanisms are under debate.The importance of the relative humidity (RH) on the rate of the solid- state imines synthesis has been recently reported.7 The significance of the last mentioned publication directed us to explore the influence of the size of the reactants particles on the rate of the synthesis. The solid reactants were gently mixed without grinding and the advancement of the syntheses was monitored in-situ by means of the PXRD. The study was carried out on reactants used as purchased and on reactants grinded before use. The relative value of the intensities of the diffraction maxima at chosen 2θ angles were plotted against ageing time to get insight into the reaction kinetics.

In-situ; PXRD; imines

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