Physicochemical propel ties of plant protection substances: I polymorphism and binary systems of triadimenol

The fungicide triadimenol consists of a mixture of two diastereoisomers. Diastereoisomer A (1RS,2SR) could be obtained from the mixture by fractionated crystallization from ethanol/water and toluene, successively, whereas diastereoisomer B (1RS,2RS) could be separated by column chromatography on a silica gel column using ethylacetate as eluent. Four different crystal forms of diastereoisomer A could be derived. The modifications were characterized by means of thermal analysis (thermomicroscopy, DSC), FTIR-spectroscopy, FT-Raman-spectroscopy and powder X-ray diffraction. as well as pycnometry. The thermodynamic relationships are illustrated in a semi-schematic energy/temperature-diagram which provides information about the relative thermodynamic stabilities and physical properties of the four crystal forms. Mod. II (m.p. 132 degreesC, DeltaH(f) 33.1 +/- 0.2 kJ.mol(-1), density 1.271 +/- 0.001 g.cm(-3)) was obtained from toluene after the separation of diastereoisomer A and is enantiotropically related to mod. I (m.p, 138 degreesC, DeltaH(f) 32.0 +/- 0.2 kJ.mol(-1). density 1.243 +/- 0.001 g.cm(-3)). The transition point of mod. II with mod. I was determined between 30 and 40 degreesC, which means that mod. II is thermodynamically stable at ambient conditions. Mod. III (m.p. 112 degreesC, DeltaH(f) 2-5.1 +/- 0.5 kJ.mol(-1)) and mod. IV were obtained from the melt. Furthermore, the phase diagrams of the binary systems of diastereoisomer B and the four modifications of diastereoisomer A were calculated by means of the experimentally obtained thermodynamical data.