Extraction thermodynamics of Th(IV) in various aqueous organic systems

Thermodynamic studies on solvent extraction of Th(IV) have been carried out using TBP and HDEHP as extractants in toluene from aqueous bromide and iodide media containing Arsenazo-III as a colouring reagent. This reagent was used for the spectrophotometric determination of Th(IV). The study was carried out at T = {(283, 298, 313) ± 1} K to evaluate lg K_ex as well as the thermodynamic functions ΔG^°, ΔH^°, and ΔS^° of the extraction reactions. The extracted species and the overall extraction mechanisms are postulated.     

Benzotriazole-mediated alkoxyalkylation and acyloxyalkylation

Reactions of readily available and stable 1-(α-alkoxyalkyl)benzotriazoles type 9a,b and 10a-d with a variety of silyl enol ethers 11 or 1,3-dicarbonyl compounds 13 give the expected ketones 12a-l (60-92%), β-keto esters 14a,b (62-67%), and malonates 14c,d (79-88%) in which a tetrahydrofuran or tetrahydropyran moiety has been introduced at the α position. 1-(Benzotriazol-1-yl)alkyl esters 7 are converted by cyanide anion into cyanohydrin esters 15a-i (55-98%).     

Thermodynamics of the solvent extraction of Zr(IV) by Amberlite LA-2, TBP and HDEHP from different aqueous media

Solvent extraction on Zr(IV) were carried out at 5, 25 and 40 °C using Amberlite LA-2, TBP and HDEHP in toluene or kerosene from solutions of HCl, HBr or KI. The equilibrium constant K _ex as well as the thermodynamic functions DG°, DH° and DS° of the nine extraction systems were deduced. The overall extraction equilibria were postulated from the obtained data.     

Thermogravimetric and spectroscopic characterization of trivalent lanthanide chelates with some schiff bases

Solid complexes of two derivatives of Schiff bases SAT and SAZ with Pr(III), Nd(III), Gd(III), Dy(III), Ho(III), Er(III) and Yb(III) were prepared and characterized by elemental analysis , IR spectra and TG. The suggested formula of the obtained solid complexes is [MLCl₂(H₂O)n] for sat and [MLCl (H₂O)n] for SAZ where M=trivalent lanthanide ion, L=deprotonated ligand and n=2-3. The TG gives information about the coordinated water molecules, thermal stability and the coordination number of M which was found to be 6–8. A scheme of thermal decomposition of the complexes is also proposed. Comparison of the IR spectra of the ligands with those of their complexes indicate the center of chelation in SAT and SAZ which act as tridentate ligands. This revised version was published online in July 2006 with corrections to the Cover Date.     

Darstellung,spektroskopische Untersuchungen und Kristallstruktur von [Cl4SbO2P(CH3)2]2

Preparation, Spectroscopic and Crystal Structure Investigations of [Cl₄SbO₂P(CH₃)₂]₂ [Cl₄SbO₂P(CH₃)₂]₂ was prepared from SbCl₅ and HOP(O)(CH₃)₂ in CH₂Cl₂. The compound crystallizes in the space group P2₁/n with two dimeric units per unit cell; the lattice constants are a = 875, b = 1306, c = 923 pm and β 97.1°. Structural investigation by X-ray diffraction methods showed the Sb atoms in the dimeric units to be linked by O? P? O-bridges of the dimethylphosphinate groups to Sb₂O₄P₂ eight-rings of approximate symmetry C_2h. The vibrational spectrum (i.r., Raman) and the n.m.r. spectra (³¹P, ¹H) consist with this structure.     

Colorimetric determination of pyridoxine in pharmaceutical preparations

Summary The USP method for the determination of pyridoxine hydrochloride in pharmaceutical preparations has been modified to increase the stability of the colour, the speed of determination and the sensitivity. The reaction is carried out in propan-2-ol medium instead of water triethanolamine is used as the buffer, and iodine is used as oxidant when necessary. The colour is stable for about 45 min, the sensitivity of the reaction is greatly increased and the method takes only about a fifth of the time of the USP method.

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Kolorimetrische Bestimmung von Pyridoxin in pharmazeutischen Präparaten

Zusammenfassung Die USP-Methode zur Bestimmung von Pyridoxinhydrochlorid in pharmazeutischen Präparaten wurde modifiziert, um die Beständigkeit der Farbe, die Geschwindigkeit der Bestimmung und deren Empfindlichkeit zu verbessern. Statt in Wasser wird die Reaktion in Propan-2-ol durchgeführt, wobei Triethanolamin als Puffer und Jod — wenn nötig — als Oxydationsmittel verwendet werden. Die Farbe ist ungefähr 45 min beständig, die Empfindlichkeit der Reaktion stark verbessert und die zur Durchführung der Methode erforderliche Zeit beträgt etwa ein Fünftel im Vergleich zur USP-Methode.

     

Crystal Structures and Raman Spectra of cis‐[SnCl4(H2O)2]·2H2O,cis‐[SnCl4(H2O)2]·3H2O, [Sn2Cl6(OH)2(H2O)2]·4H2O,and [HL][SnCl5(H2O)]·2.5H2O (L=3‐acetyl‐5‐benzyl‐1‐phenyl‐4, 5‐dihydro‐1, 2, 4‐triazine‐6‐one oxime,C18H18N4O2)

The complexes cis‐[SnCl₄(H₂O)₂]·2H₂O ( 1 ), [Sn₂Cl₆(OH)₂(H₂O)₂]·4H₂O ( 3 ), and [HL][SnCl₅(H₂O)]·2.5H₂O ( 4 ) were isolated from a CH₂Cl₂ solution of equimolar amounts of SnCl₄ and the ligand L (L=3‐acetyl‐5‐benzyl‐1‐phenyl‐4, 5‐dihydro‐1, 2, 4‐triazine‐6‐one oxime, C₁₈H₁₈N₄O₂) in the presence of moisture. 1 crystallizes in the monoclinic space group Cc with a = 2402.5(1) pm, b = 672.80(4) pm, c = 1162.93(6) pm, β = 93.787(6)° and Z = 8. 4 was found to crystallize monoclinic in the space group P2₁, with lattice parameters a = 967.38(5) pm, b = 1101.03(6) pm, c = 1258.11(6) pm, β = 98.826(6)° and Z = 2. The cell data for the reinvestigated structures are: [SnCl₄(H₂O)₂]·3H₂O ( 2 ): a = 1227.0(2) pm, b = 994.8(1) pm, c = 864.0(1) pm, β = 103.86(1)°, with space group C2/c and Z = 4; 3 : a = 961.54(16) pm, b = 646.29(7) pm, c = 1248.25(20) pm, β = 92.75(1)°, space group P2₁/c and Z = 4.     

New and selective HPTLC—Densitometric method for determination of pioglitazone hydrochloride

JPC – Journal of Planar Chromatography – Modern TLC - New sensitive and selective HPTLC-densitometric method has been developed for the determination of pioglitazone hydrochloride. The...     

Thermal and spectral studies on complexes derived from tetradentate Schiff bases

Several new complexes of Schiff bases ligands H₄La and H₄Lb with transition metal ions such as Cr(III), Fe(III), Co(II) and Zn(II) are synthesized. Elemental analysis, infrared, UV–Vis and thermal analysis, as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. A square planar geometry is suggested for Zn(II) complexes, while an octahedral geometry suggested for the Cr(III), Fe(III) and Co(II) complexes. The thermal decomposition of complexes was found to be first order reaction and the thermodynamic parameters corresponding to the different decomposition steps were reported.