B. Pauvert

Effect on composition of dry mechanical grinding of calcium phosphate mixtures

For diverse reasons, calcium phosphates used to prepare hydraulic calcium phosphate cements can be ground mixed. The grinding with a rotating micromill of monocalcium phosphate monohydrate or anhydrous, dicalcium phosphate dihydrate or anhydrous with calcium oxide, calcium hydroxide, calcium carbonate, tetracalcium phosphate, or alpha- or beta-tricalcium phosphate was studied for different calcium to phosphate (Ca/P) ratios, rotating rates, masses of balls, and environmental conditions. During dry grinding by ball milling, anhydrous or hydrated acid calcium phosphates can mechanochemically react with anhydrous or hydrated basic calcium salts to form dicalcium phosphate dihydrate or anhydrous, noncrystalline calcium phosphate, and/or calcium deficient or stoichiometric hydroxyapatite, depending on the Ca/P ratio in the mixture and the time of grinding. The reaction rate is a function of the rotation rate and the mass of the balls. Water is not necessary to initiate the reaction but facilitates it because hydrated salts react faster than the corresponding anhydrous salts. Neither carbon dioxide nor carbonate ions seem to have any influence on the transformation kinetics. The transformations that occur during grinding influence the final mechanical properties of hydraulic calcium phosphate cements prepared from these materials. Thus, if a grinding step of the starting materials is planed, the grinding conditions will have to be particularly well defined to obtain reproducible results.

Structure of polymorph II of (1R,3S)-1,2,2-trimethyl-3-(4-methylthiobenzoyl)-cyclopentanecarboxylic acid

C17H22O3S, M(r) = 306.407, orthorhombic, P2(1)2(1)2, a = 13.327 (5), b = 19.277 (8), c = 6.361 (2) angstrom, V = 1634 (1) angstrom3, Z = 4, D(x) = 1.245 Mg m-3, lambda(Cu Kalpha) = 1.54178 angstrom, mu = 1.77 mm-1, F(000) = 656, T = 293 K, R = 0.043 for 2574 observed reflections. Two crystalline forms of the title compound have been obtained but only one (form II) has given suitable crystals for X-ray structure analysis. The five-membered ring has an envelope conformation with C(2) 0.60 (1) angstrom out of the plane defined by the other four atoms. The absolute configuration has been established and appears to be identical to that of camphoric acid used in the synthesis. Molecules form dimers around the twofold axis by means of hydrogen bonds between their carboxylic groups.

Polymorphisme et analyse du comportement thermique d'une serie de 3-(α-hydroxy imino aryl) 1,2,2-trimethyl cyclopentane carboxylate

The infrared,1H NMR and X-ray diffraction characteristics of a series of 3-(α-hydroxy-imino-aryl)-1,2,2-trimethyl cyclopentane carboxylate are reported. The thermal analysis of this series has been studied by differential scanning calorimetry. The results show a large variety of thermal behaviours with some of the compounds exhibiting polymorphism and the two types of isomers were detected.ZusammenfassungEs werden die Infrarot-, die1H NMR- und Röntgendiffraktionsmerkmale einer Reihe von 3-(-Hydroxyiminoaryl)-1,2-2-trimethylcyclopentancarboxylate dargelegt. Die Thermoanalyse dieser Reihe wurde mittels DSC durchgeführt. Die Ergebnisse zeigen ein weites Feld thermischen Verhaltens, wobei einige der Verbindungen Polymorphismus aufweisen und zwei Typen von Isomeren festgestellt werden konnten.

Polymorph(ii) of Methyl 3-(4-ethoxy-alpha-hydroxyiminobenzyl)-1,2,2-trimethylcyclopentanecarboxylate

The title compound, C19H27NO4, is an intermediate product in the synthesis of oxazepinic and piperidinic compounds. Two crystalline forms of the title compound have been obtained but only one [form (II)] gave suitable crystals for X-ray structure analysis. The five-membered ring has an envelope conformation with C(2) 0.60 (5) angstrom out of the plane defined by the other four atoms. It has been established that the oxime group has a syn conformation and the two enantiomers form a dimer around the centre of symmetry by means of hydrogen bonds between their oxime groups.