Study of transition temperature through mixed crystal formation,IV

The study of homogeneous distribution coefficients in determining the transition temperatures of isomorphologically analogous components and in predicting the existences of some new unstable compounds has been carried out in detail with special references to vitriols of nickel, manganese, zinc, copper and magnesium. In the course of the investigation with NiSO₄·7H₂O as host and⁵⁴Mn as guest, the transition temperature of orthorhombic NiSO₄·7H₂O was shown to be 26.5 °C, and with orthorhombic ZnSO₄·7H₂O and MgSO₄·7H₂O as host and copper sulphate as guest, the limits of existences of orthorhombic CuSO₄·7H₂O and newly predicted CuSO₄·6H₂O were found to be 13.5° to 44 °C and 44° to 51 °C, respectively. In addition, the transition temperatures of orthorhombic MnSO₄·7H₂O (10 °C), stable NiSO₄·7H₂O (30.5±5 °C) and orthorhombic ZnSO₄·7H₂O (39 °C) were verified. The new method of approach is very simple, reproducible and easily adaptable.     

Synthesis of certain 6-alkylthio-2,2′-anhydro-5-azauridines

β-D-Arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione ( 7b ) and its t-butyldimethylsilyl protected counterpart 7a were synthesized by treating the appropriate 2-amino-β-D-arabinofurano[1′,2′:4,5]-2-oxazoline with ethoxycarbonyl isothiocyanate. These 2,2′-anhydro-s-triazine nucleosides were then subjected to alkylation under similar reaction conditions. Alkylation of 3′,5′-bis(O-t-butyldimethylsilyl)-β-D-arabinofurano[1′,2′:-4,5]oxazolo-s-triazin-4-one-6-thione ( 7a ) provided the targeted S-alkylated nucleosides, i.e., the C6-SCH₃ ( 9a ), C6-SCH₂-CH = CH₂ ( 10a ), and C6-S-CH₂-C = CH ( 11a ), in reasonable yields. Attempted deprotection of these nucleosides failed. In order to circumvent this problem, 7b was alkylated with the same reagents. In each case, instead of the expected S-alkylated anhydronucleosides, a mixture of the 5-N-alkylanhydro-s-triazine-4,6-dione and 5-N-alkylanhydro-s-triazin-4-one-6-thione derivatives were obtained. The 2,2′-anhydro linkage of 7a was also found to be more stable than the s-triazine ring to mild base. Basic conditions displaced the C6-sulfur substituent and eventually caused ring opening of the s-triazine aglycone.     

A simple method for the preparation of pure hafnium

The separation of zirconium and hafnium by fractional precipitation as pyrophosphate¹ has been extended for the preparation of pure hafnium. The favourable uptake of hafnium, in spite of the decreasing tendency of partition factor when hafnium concentration is high, is maintained for all concentration of hafnium (relative to zirconium). Particularly significant is the fact that at very high concentrations of hafnium (at≈84%) the uptake of zirconium sharply falls. So pure hafnium can be prepared from natural zirconium by a simple process of eight or nine stages of fractional precipitations as pyrophosphate. This process yields reactor grade zirconium on the one side and pure hafnium on the other side.     

Laser induced optoacoustic spectroscopy of benzil: Evaluation of structural volume change upon photoisomerization

The cis-skew to trans-planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution.     

Transition metal catalysed Grignard-like allylic activation across tetragonal tin(II) oxide

The reaction of allyl halide and a carbonyl compound under the aegis of tetragonal tin(II) oxide and catalyticd ⁸,d¹⁰ metal complexes provides the corresponding homoallylic alcohol, via a novel allyl tin intermediate.     

Silicon–oxygen‐bonded oligomers having thermoelectric switching properties

The electrical properties of siloxane oligomers prepared from the reaction of 1,4‐naphthalenediol or 1,4‐naphthoquinone with diphenylsilane using different palladium catalysts, such as PdCl₂, Pd(TMEDA)Cl₂, Pd(TEEDA)Cl₂ (where TMEDA = N,N′‐tetramethylethylenediamine, TEEDA = N,N′‐tetraethylethylenediamine), are dependent on the catalyst. Thermoelectric switching properties can be obtained from the siloxane prepared from the coupling reaction of diphenylsilane with 1,4‐naphthoquinone or 1,4‐naphthalenediol using Pd(TMEDA)Cl₂ as catalyst. Copyright © 2001 John Wiley & Sons, Ltd.     

Unitary group adapted state specific multireference perturbation theory: Formulation and pilot applications

We present here a comprehensive account of the formulation and pilot applications of the second‐order perturbative analogue of the recently proposed unitary group adapted state‐specific multireference coupled cluster theory (UGA‐SSMRCC), which we call as the UGA‐SSMRPT2. We also discuss the essential similarities and differences between the UGA‐SSMRPT2 and the allied SA‐SSMRPT2. Our theory, like its parent UGA‐SSMRCC formalism, is size‐extensive. However, because of the noninvariance of the theory with respect to the transformation among the active orbitals, it requires the use of localized orbitals to ensure size‐consistency. We have demonstrated the performance of the formalism with a set of pilot applications, exploring (a) the accuracy of the potential energy surface (PES) of a set of small prototypical difficult molecules in their various low‐lying states, using natural, pseudocanonical and localized orbitals and compared the respective nonparallelity errors (NPE) and the mean average deviations (MAD) vis‐a‐vis the full CI results with the same basis; (b) the efficacy of localized active orbitals to ensure and demonstrate manifest size‐consistency with respect to fragmentation. We found that natural orbitals lead to the best overall PES, as evidenced by the NPE and MAD values. The MRMP2 results for individual states and of the MCQDPT2 for multiple states displaying avoided curve crossings are uniformly poorer as compared with the UGA‐SSMRPT2 results. The striking aspect of the size‐consistency check is the complete insensitivity of the sum of fragment energies with given fragment spin‐multiplicities, which are obtained as the asymptotic limit of super‐molecules with different coupled spins. © 2015 Wiley Periodicals, Inc.     

Wettability, FTIR and dielectric studies of 1,4-dioxane and water system

Wettability studies are of importance for electronic devices. Various methods are known to convert the hydrophobic substrates to hydrophilic substrates, but the studies on the relative dependence of wettability with varying concentrations of an aqueous system are meager. The wetting of different substrates with varying concentration of 1,4-dioxane in water is investigated and the results of concentration dependence of wetting are presented. The FTIR spectrum shows a blue shift of the OH peak--a feature typical of aqueous-1,4-dioxane systems. Concentration dependence of dielectric permittivity of this system also showed an anomaly.