Competing A-site and B-site driven ferroelectric instabilities in the (1-x)PbTiO3-(x)BiAlO3 system

The system (1-x)PbTiO3-(x)BiAlO3 has been investigated with regard to its solid solubility, crystal structure, microstructure, and ferroelectric transition. The unit cell volume and the tetragonality exhibit anomalous behavior near x=0.10. The Curie point (T-C) of PbTiO3 was however found to be nearly unchanged. The study seems to suggest that the decrease in the stability of the ferroelectric state due to dilution of the Ti-sublattice by smaller sized Al+3 ions is compensated by the increase in the ferroelectric stability by the Bi+3 ions.

Metabolism of 1,8-Cineole in Rat: Its Effects on Liver and Lung Microsomal Cytochrome P-450 Systems

The monoterpene cyclic ether, cineole (l,8-cineole, I) also known as eucalyptol, is a component of many essential oils and is widely distributed in nature. It is extensively used in pharmaceutical preparations for external application and also as a nasal spray. It was reported earlier that cineole when administered to sheep may be largely oxidized in the system (Scheline 1978). However the mode of metabolism of cineole is not known. Hence the present study was undertaken to investigate the metabolic fate of this ubiquitous terpenoid following its administration to rats by gastric intubation.

Complexes Of Imidazoline-2-Thione And Its 1-Methyl Analogue With Cu(Ii), Zn(Ii), Cd(Ii) And Hg(Ii) Salts

The reaction of Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides with imidazoline-2-thione (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (where M=Cu(I)); copper(II) halides yield Cu(I) complexes. On the basis of infrared and 13C n.m.r.

Conformations Of Peptides Containing 1-Aminocyclohexane-Carboxylic Acid (Acc6) - Crystal-Structures Of 2 Model Peptides

The crystal structures of two peptides containing 1-aminocyclohexanecarboxylic acid (Acc6) are described. Boc-Aib-Acc6-NHMe · H2O adopts a β-turn conformation in the solid state, stabilized by an intramolecular 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The backbone conformational angles (φAib = – 50.3°, ψAib = – 45.8°; φAcc6 = – 68.4°, ψAcc6 = – 15°) lie in between the values expected for ideal Type I or III β-turns. In Boc-Aib-Acc6-OMe, the Aib residue adopts a partially extended conformation (φAib = – 62.2°, ψAib = 143°) while the Acc6residue maintains a helical conformation (φAcc6 = 48°, ψAcc6= 42.6°). 1H n.m.r. studies in CDCl3 and (CD3)2SO suggest that Boc-Aib-Acc6-NHMe maintains the β-turn conformation in solution.

The ethyl, 1- and 2-propyl, and other simple alky carbanions do not exist

A combination of experimental data and theoretical calculations has been used to estimate the electron affinities of simple primary, secondary, and tertiary alkyl radicals and the proton affinities of the corresponding anions. With the exception of cyclopropyl, such carbanionsâ are indicated to be unstable towards loss of an electron and are not expected to exist as long-lived species in the gas phase.

Stereochemistry of Peptides Containing 1-AminocyclopentanecarboxylicA cid ( Am5): Solution and Solid-state Conformations of Boc-Acc '-Acc'-NHMe

The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a -turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III -turn conformation in the solid state stabilized by a 4 1 hydrogen bond between the Boc CO and methylamide NH groups. The , values for both Acc5 residues are close to those expected for an ideal 310-helical conformation ( ± 60°, ±30°).

Determination of the thermodynamic properties of xMgO + (1 x)MnO (s, sln) from a solid-electrolyte galvanic cell in the temperature range 1163 to 1318 K

The thermodynamic activities of MgO in the NaCl-type solid solutions which can exist in xMgO + (1 x)MnO have been determined in the temperature range 1163 to 1318 K from a solid-state galvanic cell incorporating MgF2 as the solid electrolyte. The activities of MnO have been calculated by a graphical Gibbs-Duhem integration method. The activities of both the components exhibit positive deviations from ideality over the entire composition range. The excess molar enthalpies are found to be positive. Further, xMgO + (1 - x)MnO does not conform to regular-solution behaviour. The origin of the excess thermodynamic properties is discussed in relation to the cationic size disparity and the crystal-field effects.

1-(2,4-Dichlorophenyl)-3-[4-(dimethylamino)-phenyl]prop-2-enone

In the title compound, C17H15Cl2NO, the dimethylaminophenyl group is close to coplanar with the central propenone group [dihedral angle =13.1 (1)degrees between the mean planes], while the dichlorophenyl group is twisted from the plane [dihedral angle = 64.0 (1)degrees].In the crystal, C-H center dot center dot center dot O and weak C-H center dot center dot center dot pi interactions are formed between molecules.

4-(4-Methoxyphenyl)-1-phenylpyridine-2,6(1H,3H)-dione

In the title compound, C18H15NO3, the pyridine-2,6-dione ring adopts an envelope conformation. The phenyl ring lies approximately perpendicular to the mean plane of the pyridine-2,6-dione ring [dihedral angle =81.5 (1)degrees], while the methoxyphenyl ring is tilted to the same plane by a dihedral angle of 34.8 (1)degrees. Intermolecular C-H center dot center dot center dot O interactions link the molecules into chains along [100].

4-[2-(1-Acetyl-2-oxopropylidene)-hydrazino]-N-(pyrimidin-2-yl)benzenesulfonamide

In the title compound, C15H15N5O4S, the dihedral angle between the pyrimidine and benzene rings is 84.56 (2)degrees. Intramolecular hydrazine-carbonyl N-H center dot center dot center dot O and intermolecular sulfonamide-pyridimine N-H center dot center dot center dot N hydrogen bonds stabilize the molecular and crystal structures, respectively.

Proton magnetic resonance study of molecular dynamics in (NH4)2CdI4

Proton magnetic resonance and spin-lattice relaxation studies have been carried out on (NH4)2CdI4 as a function of temperature (77–400 K) and Larmor frequency (10, 20 and 30 MHz). The T1 data indicate isotropic tumbling of ammonium ions at equivalent sites till 160 K. There is an indication of a phase transition at 265 K, the activation energy for molecular reorientation increases from 2.8 kcal/mole to 4.6 kcal/mole. The relaxation results and the linewidth data support the presence of two inequivalent sites at low temperatures, one having an environment corresponding to near-rigid-lattice limit and the other undergoing fast reorientations. The behaviour of the free induction decay with temperature below 120 K suggests a coherent motion for the faster species.

A computerized methodology for structural synthesis of kinematic chains: Part 1- Formulation

In an effort to develop a fully computerized approach for structural synthesis of kinematic chains the steps involved in the method of structural synthesis based on transformation of binary chains [38] have been recast in a format suitable for implementation on a digital computer. The methodology thus evolved has been combined with the algebraic procedures for structural analysis [44] to develop a unified computer program for structural synthesis and analysis of simple jointed kinematic chains with a degree of freedom 0. Applications of this program are presented in the succeeding parts of the paper.

Thermally Induced Acyl Migration in Salicylamides. 1. Structures of the Reactants, O-Acetylsalicylamide and O-Benzoylsalicylamide

O-Acetylsalicylamide (Ia), C9H9NO3, M r =179.18, monoclinic, P2Jc, a=8.155(5), b=8.571 (2), c= 13.092 (3)A, fl=99.54 (5) ° , V= 902.4(6)A 3, Z=4, Dm=l.31, Dx=l.319gcm -3, 2(Mo Ka) = 0.71069 A,/~ = 1.08 cm -1, F(000) = 376, T = 295 K, R = 0.076 for 1604 reflections. O-Benzoylsalicylamide (Ib), C14HtlNO 3, M,=241.2, monoclinic, P2t/e, a=9.423(1), b=5.116(1), e= 26.424 (2) A, fl= 103.97 (1)% V= 1236.2 (3)/~3, Z= 4, D~ = 1.28, D x = 1.296 gcm -3, ,;L(Cu Ks) = 1.5418 A, p = 7.71 cm-', F(000) = 504, T= 295 K, R =0.050 for 2115 reflections. The dihedral angles between the amide group and the benzene ring are 39.9 ° (Ia) and 37.9 ° (Ib), whereas between the acyl group and the benzene ring they are 78.1 ° (Ia) and 93.4 ° (Ib). The differences in the packing of the two structures are brought out in terms of the observed hydrogen-bonding patterns. Based on the crystallographic results, an intramolecular mechanism for the migration of the acyl group from the O to the N position is suggested in both compounds.

On Coloration of Polyacrylonitrile: A Nuclear Magnetic Resonance Study

Coloration in polyacrylonitrile can be induced in three distinct ways: by heat treatment, by treatment with base, or during synthesis of the polymer itself using ionic initiators at relatively higher temperatures. The present investigation employing 'H and NMR spectroscopy has revealed some common features in colored polyacrylonitrile irrespective of ita mode of coloration. All colored polyacrylonitriles give an additional peak around S 2.7 in 'H NMR spectra and, except for heat-treated polyacrylonitrile, one extra group of peaks in the region 8 12-16 in 13C NMR spectra. The former peak has been attributed to methine and/or methylene protons in branched and/or cyclized structures, while the latter peak has been attributed to methylene carbon atoms in the branched structure. Colorless polyacrylonitriles have been found to be predominantly heterotactic, while colored polyacrylonitriles have been found to have appreciable isotactic contribution.