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Hydrated Forms (hydrated + form)

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Chemistry100%

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Hydrated forms of N -[(3R)-3-(4-methyl-3,5-dioxo-1,2,4-triazolidin-1-yl)-2-methyl­ene­butano­yl]-(1S,2R)-bornane-10,2-sultam and its enanti­omer

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
Yiannis Elemes
Triazolidinediones react with each enantiomeric bornanesultam derivative of tiglic acid to produce the appropriate ene adduct in high yield and with excellent regioselectivity and diastereo­selectivity. The optically pure products, viz. N -[(3R)-3-(4-methyl-3,5-dioxo-1,2,4-triazolidin-1-yl)-2-methyl­enebutano­yl]-(1S,2R)-bornane-10,2-sultam 0.15-hydrate, C18H26N4O5S·0.15H2O, and its enantiomer N -[(3S)-3-(4-methyl-3,5-dioxo-1,2,4-triazolidin-1-yl)-2-methyl­enebutano­yl]-(1R,2S)-born­ane-10,2-sultam 0.35-hydrate, C18H26N4O5S·0.35H2O, have been characterized by spectroscopy and single-crystal X-ray analysis. Their structures are the result of C,- re attack of the enophile on the double bond of the alkene. [source]

Polymorphism and pseudopolymorphism of salicaine and salicaine hydrochloride crystal polymorphism of local anaesthetic drugs, part V

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2006
A.C. Schmidt
Abstract The local anaesthetic drug salicaine hydrochloride (hydroxytetracaine hydrochloride, 4-butylamino-2-hydroxybenzoic acid 2-dimethylaminoethyl ester hydrochloride, SLCHC) and the free-base salicaine (SLC) were characterized by thermal analysis, vibrational and solid-state NMR-spectroscopy, X-ray powder diffraction, X-ray single crystal structure analysis, and water vapor sorption analysis. Additionally, the crystal structures of the anhydrate mod. II° (monoclinic, space group P21/n), the hydrated mod. I (triclinic, space group ), and of the free base (SLC) in the form of the hemihydrate (triclinic, space group ) are discussed. Mod. II° of the polymorphic SLCHC is the thermodynamically stable form at room temperature and is present in commercial products mostly contaminated with a hydrated form that is isomorphic with mod. I. Mod. II° crystallizes from most organic solvents and from the melt below 110°C. Mod. I crystallizes from the melt at temperatures above 110°C, and additionally appears on dehydration of the hydrated mod. I. A third polymorph monotropically related to mod. II° was found by freeze-drying. The free-base SLC was found to crystallize from ethanol/water as a triclinic hemihydrate. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:1097,1113, 2006 [source]

Quantum chemical studies on molecular structural conformations and hydrated forms of salicylamide and O-hydroxybenzoyl cyanide

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2005
K. Anandan
Abstract Ab initio and density functional theory (DFT) methods have been employed to study the molecular structural conformations and hydrated forms of both salicylamide (SAM) and O-hydroxybenzoyl cyanide (OHBC). Molecular geometries and energetics have been obtained in the gaseous phase by employing the Møller,Plesset type 2 MP2/6-311G(2d,2p) and B3LYP/6-311G(2d,2p) levels of theory. The presence of an electron-releasing group (SAM) leads to an increase in the energy of the molecular system, while the presence of an electron-withdrawing group (OHBC) drastically decreases the energy. Chemical reactivity parameters (, and ,) have been calculated using the energy values of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) obtained at the Hartree,Fock (HF)/6-311G(2d,2p) level of theory for all the conformers and the principle of maximum hardness (MHP) has been tested. The condensed Fukui functions have been calculated using the atomic charges obtained through the natural bond orbital (NBO) analysis scheme for all the optimized structures at the B3LYP/6-311G(2d,2p) level of theory, and the most reactive sites of the molecules have been identified. Nuclear magnetic resonance (NMR) studies have been carried out at the B3LYP/6-311G(2d,2p) level of theory for all the conformers in the gaseous phase on the basis of the method of Cheeseman and coworkers. The calculated chemical shift values have been used to discuss the delocalization activity of the electron clouds. The dimeric structures of the most stable conformers of both SAM and OHBC in the gaseous phase have been optimized at the B3LYP/6-311G(2d,2p) level of theory, and the interaction energies have been calculated. The most stable conformers of both compounds bear an intramolecular hydrogen bond, which gives rise to the formation of a pseudo-aromatic ring. These conformers have been allowed to interact with the water molecule. Special emphasis has been given to analysis of the intermolecular hydrogen bonds of the hydrated conformers. Self-consistent reaction field (SCRF) theory has been employed to optimize all the conformers in the aqueous phase (, = 78.39) at the B3LYP/6-311G(2d,2p) level of theory, and the solvent effect has been studied. Vibrational frequency analysis has been performed for all the optimized structures at MP2/6-311G(2d,2p) level of theory, and the stationary points corresponding to local minima without imaginary frequencies have been obtained for all the molecular structures. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]