Enthalpy of hydrogen bonded alcohol-butyl amine complexes by a simpler calorimetric method

The heats of mixing ofn-butyl amine with methanol andn-propanol have been determined at 30° C and the enthalpies of alcohol-amine complex formation have been calculated by thermochemical cycle. The enthalpies of complex formation of butyl amine with methanol andn-propanol were found to be-44.3 kJ/mole and-39.4 kj/mole respectively. The heats of mixing of synthetically prepared 1:1 molar mixtures of n-butyl amine with methanol, ethanol andn-propanol withn-hexane have also been determined at 30° C. The enthalpy of amine-alcohol complexes was obtained from the partial molar heats of dissociation of the complexes inn-hexane. The values agree with those obtained by the thermochemical cycle method. NCL Communication No. 2561.     

Preparation and analytical properties of a chelating resin functionalized with 1-hydrazinophthalazine ligand

A poly[styrene-co-(divinylbenzene)] resin (XAD-4) functionalized with 1-hydrazinophthalazine ligand has been prepared and its analytical properties investigated. The pH dependence of sorption of metal ion on the resin has been determined for Cu(II), Ni(II), Co(II), Zn(II), Cd(II), Pb(II), Fe(III) and Cr(III). Trace amounts of these metal ions were quantitatively retained on the resin and recovered by eluting with 1 mol l(-1) hydrochloric acid. The resin was found to be selective for Fe(III) and its separation from other metal ions was carried out effectively. Metal ions concentrations were determined using AAS.     

Sorption studies of europium(III) on hydrous silica

Summary Sorption behavior of europium, Eu³⁺, on SiO₂ ^. xH₂O (silica gel) has been investigated as a function of time, the amount of silica gel, Eu³⁺ concentration, the ionic strength, and pH (in absence and in presence of carbonate). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity of silica gel was determined to be in the range of (2.62-8.00) ^. 10^-7 mol/g at pH 5.30±0.05 and 0.20M NaClO₄. The mean energy of sorption was calculated to be 13.50±0.05 kJ/mol from the D-R isotherm, suggesting the involvement of ion-exchange reactions in the sorption process. Sorption of Eu³⁺ decreased with increased ionic strength. A gradual decrease in pH with increased ionic strength supports the involvement of an ion-exchange mechanism in the sorption process. The diffusion coefficient of Eu³⁺ ion on silica gel was calculated as (3.98±0.12) ^. 10^-13 m^{2 .} s^-1 under the particle diffusion-controlled conditions.     

Complexation/speciation studies of Ni2+ion with ortho silicic acid in perchlorate media

Summary The complexation behavior of Ni²⁺with ortho-silicic acid (o-SA) has been studied as a function of ionic strength (I) from 0.20 to 1.00M (NaClO₄) at pcH 4.55±0.05 and 25 °C by a solvent extraction technique with bis(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stoichiometry of the extracted species was determined to be Ni(DEHP)₂(HDEHP)₂. Ni²⁺forms a 1:1 complex, Ni(OSi(OH)₃)⁺, as the predominant species withconcentrations of 1.00^. 10^-3to 1.00^. 10^-2M o-SA. The stability constant (logb₁) values for Ni(OSi(OH)₃)⁺complex formation decrease with increased ionic strength. These values have been fitted with the extended Debye-Huckel expression to obtain the value of logb₁=6.34±0.03 at I=0.00M. The data allowed the calculation of speciation of the Ni²⁺- silicate system as a function of ionic strength.     

Extraction chromatographic separation of thorium (IV) with tri-n-octylphosphine oxide (TOPO)

Thorium was extracted from a mixture of nitric acid and NaNO₃ of 0.01M each at pH 2.2 on a column of silica gel coated with TOPO. Thorium was separated from alkalis, alkaline earths, chromium, iron, cobalt, nickel, zinc, cadmium, mercury, lead, trivalent rare earths, platinum group metals, chloride, phosphate and acetate in binary mixtures by selective extraction of thorium. Thorium was separated from cerium (IV), zirconium, uranium and molybdenum by selective elution of thorium with 0.01M H₂SO₄. The method was extended for the analysis of thorium in monozite ore.     

Synthesis of some new fluorine-containing 5-amino-1,3-disubstituted pyrazoles and 1H-pyrazolo[3,4-b]pyridines

Nine new fluorine containing 5-amino-1,3-disubstituted pyrazoles have been synthesized and characterized by spectral studies. Condensation reactions of these 5-amino-1,3-disubstituted pyrazoles with fluorinated 1,3-diketones in the presence of glacial acetic acid have been studied and the structures of the resulting 1H-pyrazolo[3,4-b]pyridines have been confirmed by ir, pmr and ¹⁹F nmr spectral studies.     

The synthesis of indolo- and pyrrolo[2,1-a]isoquinolines

The synthesis of fused isoquinolines from N-benzyl protected indoles and pyrroles is described. For example, treatment of t-butyl-2-(2-formyl-3,4-dihydro-1-naphthalenyl)-3-methyl-1H-indole-1-carboxylate with KOBu^t in DMF provided 14-methyl-8-phenylbenzo[h]indolo[2,1-a]isoquinoline in good yield. Analogous N-benzylpyrrole precursors could similarly be cyclized to give pyrrolo[2,1-a]isoquinolines.     

Bounds to electron-repulsion energies

A review of rigorous bounds to electron-repulsion integrals for atoms and molecules is presented. Inequalities involving direct (classical) as well as indirect (quantal) Coulomb energies are discussed. This is followed by an account of two-electron integrals in a Hartree Fock context over Gaussian basis-sets. Novel rigorous bounds to these integrals are derived and tested for some organic molecules. Connections are established with the density-based inequalities presented earlier. The present results are expected to enhance the efficiency of a generalab initio Gaussian program and yet have a sound theoretical footing.     

Derivatographic studies on dehydration of salt hydrates and their deuterium oxide analogues. V

Non-isothermal thermal studies of the dehydration of the double salt hydrates of the type M(I)₂SO₄·M(II)SO₄·6H₂O and their D₂O analogues were carried out where M(I) = TI(I) and M(II) = Mg(II), Co(II), Ni(II), Cu(II) or Zn(II). Thermal parameters like activation energy, order of reaction, enthalpy change, etc. were evaluated from the analysis of TG, DTA and DTG curves. These thermal parameters were compared with those of other series, like NH₄(I), K(I), Rb(I) and Cs(I) studied earlier. On deuteration the nature of dehydration altered in the case of Tl₂Zn(SO₄)₂·6H₂O only. The thermal stability of the salt hyd discussed in relation to the salt hydrates of other series. The role of divalent cation on the thermal properties of dehydration of salt hydrates is also discussed. The order of reaction was always found unity. The values of ΔH were within ≈12–≈16 kcal mol^?1.     

Derivatographic studies on dehydration of salt hydrates and their deuterium oxide analogues. III

Dehydration of double salt hydrates of the type M(I)₂SO₄·M(II)SO₄·6H₂O where M(I)Rb(I) and M(II)Mg(II), Mn(II), Co(II), Ni(II), Zn(II) and Cu(II) has been studied by derivatograph. Thermal parameters like activation energy, order of reaction, enthalpy change etc. for each step of dehydration have been evaluated from the analyses of TG, DTA and DTG curves and these parameters are compared with corresponding salt hydrates of the NH₄ and K(I) series. These double salt hydrates are deuterated and studied similarly. Activation energies for the first step of dehydration of these salt hydrates increase with the increase of second ionisation potential of the central metal except for Mg. The nature of dehydration changes in the cases of double salt hydrates of Mg(II) and Ni(II) on deuteration. The order of reaction for each case of dehydration has been found to be unity. The enthalpy change per mole of water varies from 11.4 to 17 kcal.