Polymorphism of paracetamol

The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG _sub²⁹⁸=60.0 kJ mol⁻¹; ΔH _sub²⁹⁸=117.9±0.7 kJ mol⁻¹; ΔS _sub²⁹⁸=190±2 J mol⁻¹ K⁻¹. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition enthalpy at 298 K, ΔH _tr²⁹⁸(I→II)=2.0±0.4 kJ mol⁻¹, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based on ΔH _tr²⁹⁸ (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification II were also estimated (ΔG _sub²⁹⁸=56.1 kJ mol⁻¹; ΔH _sub²⁹⁸=115.9±0.9 kJ mol⁻¹; ΔS _sub²⁹⁸=200±3 J mol⁻¹ K⁻¹). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported found by classical thermochemical methods.     

Polymorphism of progesterone

Solid dispersions are used in pharmaceutical technology in order to improve solubility and/or dissolution kinetics of poorly water soluble drugs [1, 2, 3]. A preliminary study concerning progesterone structure after melting revealed the existence of a drug polymorphism after cooling, and gave the opportunity to specify the manufacturing conditions in order to obtain the stable form of this hormone [4]. In this work, two different types of progesterone solid dispersion have been compared. The first one is obtained by a slow cooling rate of the drug in the presence of polyoxyethylene glycol 6000 and the second one after quenching in the presence of saccharose distearate. DSC and radiocrystallographic studies of the solid dispersions served to specify the nature of the compounds obtained and to characterize the physical structure of the hormone in the solidified melts.     

氯酞菁氯铝的多晶性

制得３种不同晶型的氯酞菁氯铝，并以Ｘ－光粉末衍射（ＸＲＤ）及ＦＴ－ＩＲ表征，比较了各种晶型ＡｌＣｌＰｃｃｌ室温硫化硅橡胶的吸收光谱。讨论了ＡｌＣｌＰｃＣｌ的纯化方法。     

Polymorphism in pentacene

Pentacene, C₂₂H₁₄, crystallizes in different morphologies characterized by their d(001)‐spacings of 14.1, 14.5, 15.0 and 15.4 Å. We have studied the crystal structure of the 14.1 and 14.5 Åd‐spacing morphologies grown by vapour transport and from solution. We find a close correspondence between the 14.1 Å structure reported by Holmes, Kumaraswamy, Matzeger & Vollhardt [Chem. Eur. J. (1999), 5 , 3399–3412] and the 14.5 Å structure reported by Campbell, Monteath Robertson & Trotter [Acta Cryst. (1961), 14 , 705–711]. Single crystals commonly adopt the 14.1 Åd‐spacing morphology with an inversion centre on both mol­ecules in the unit cell. Thin films grown on SiO₂ substrates above 350 K preferentially adopt the 14.5 Åd‐spacing morphology, with a slightly smaller unit‐cell volume.     

那格列奈的多晶型与溶解度

分别对那格列奈B, H和S三种晶型的溶解度、溶解热进行了测定和计算. 结果表明: 那格列奈的S晶型与临床使用的H晶型溶解度均明显大于B晶型. B, H和S三种晶型的溶解热分别为42.84, 28.44 和29.14 kJ•mol^－1. 此外, 我们还新发现了不同于B, H, S晶型的X2晶型, 并且制备出了无定型的那格列奈.     

Polymorphism of potassium-sodium tartrate tetrahydrate

A geometric model of phase equilibria between NaKC₄H₄O₆ · 4H₂O crystal hydrate polymorphs was suggested. An analytic equation for its thermodynamic potential was obtained, and the temperature dependences of heat capacity and polarization were found. An analytic form of the interrelation between the anisotropic characteristics of NaKC₄H₄O₆ · 4H₂O was obtained, and their temperature dependences were calculated over a wide temperature range including polymorphic transition points.     

Polymorphism of (+)N-tosyl-L-glutamic acid

It has been shown that polymorphism is the reason for the occurrence of (+)N-tosyl-L-glutamic acid 1 with various melting points. 1 occurs in two crystalline forms: and . Form -1 (prisms) having a melting point of 145–147°C is chemically pure and stable. Form -1, however, is unstable and is formed as a result of the stabilizing effect of an organic solvent not introduced into the structure of the crystal. At about 125°C the forms is transformed to the form. The melting point of the form depends on the amount and type of solvent contained in the crystal, which, during measurement cannot leave the system.     

Polymorphism of KNaNbOF5 crystals

X-ray crystallography is used to analyze the concomitant polymorphism of KNaNbOF₅ crystals. The second ??-modification of the compound, crystallizing in the tetragonal crystal system is found for the first time: space group P4/nmm, a = 5.9352(2) ?, c =8.5487(5) ?, V = 301.14(2) ?³, Z = 2, R1 = 0.0095. Parameters of the orthorhombic noncentrosymmetric structure of the ??-phase, previously described by Poeppelmeier et al. (J. Am. Chem. Soc., 129, 13963?C13969 (2007)), are refined and a comparative analysis of both structures is performed. The structures are characterized by the complete ordering of oxygen and fluorine atoms, the Nb-O distance in the ??-phase (1.738(1) ?) being noticeably longer than that in the ??-phase (1.709(2) ?). In ??-KNaNbOF₅, alternating NbOF₅ and NaOF₅ octahedra share vertices, while in ??-KNaNbOF₅, they share both vertices and edges. The existence of the non-polar centrosymmetric ??-modification of KNaNbOF₅ cancels the assumption of the substantial contribution of potassium cations to the polar structure of ??-KNaNbOF₅.     

Polymorphism and solvation of indomethacin

Indomethacin crystallizes from solutions in tetrahydrofuran as a solvate exhibiting the mole ratio 1 indomethacin:2 tetrahydrofuran. Upon heating, desolvation into indomethacin phase I occurs through partial amorphization and transitory formation of a phase, which is different from the crystallographically known polymorphs. The X-ray powder diffraction pattern of the solvate was tentatively indexed on a triclinic lattice (a = 31.454(5) Å, b = 17.883(3) Å, c = 10.551(2) Å, α = 70.55(2)°, β = 105.31(2)°, γ = 136.70(1)°). Assuming Z = 6 (1 indomethacin + 2 tetrahydrofuran) formula units per unit cell, the solvate’s specific volume is similar to the value calculated using additivity.     

Polymorphism and solvatomorphism of bicalutamide

Single crystals of the crystallosolvate [bicalutamide + DMSO] with 1:1 stoichiometry were grown, and their structures were solved by X-ray diffraction methods. Polymorphic modifications I and II, the amorphous state, and the DMSO crystallosolvate of bicalutamide were prepared and thermochemistry of fusion processes was studied by DSC technique. The temperature dependence of the saturated vapor pressure of polymorphic form I was obtained and the thermodynamic characteristics of the sublimation process including the crystal lattice energy were calculated. The solution enthalpies of the forms under consideration and the crystallosolvate were acquired by the solution calorimetry procedure. The phase transition enthalpies estimated for form I, form II, and the amorphous state followed the rank order: form I— > form II, form I— > amorphous state, and form II— > amorphous state. The crystal lattice energy of polymorphic form II was determined using the results of sublimation and solution calorimetric experiments. The difference between the crystal lattice energy of the crystallosolvate and unsolvated phases was observed. The dissolution kinetics of forms I, II, the amorphous state, and DMSO solvate in water were investigated.