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21.
Jaseer EA Naidu AB Kumar SS Rao RK Thakur KG Sekar G 《Chemical communications (Cambridge, England)》2007,(8):867-869
A variety of trans-beta-substituted cyclic alcohols were stereoselectively chlorinated to either the corresponding cis-chloride or trans-chloride (inversion or retention of configuration) with good to excellent yields; the stereochemical outcome is determined by the size of the ring and the nature of the beta-substituents, especially the electronegativity of the substituted atom. 相似文献
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S. Sreehari Sastry Shaik Babu T. Vishwam Ha Sie Tiong 《Journal of Thermal Analysis and Calorimetry》2014,116(2):923-935
Density (ρ), viscosity (η), and speed of sound (U) values for the binary mixture systems of methyl benzoate + 2-propanol and ethyl benzoate + 2-propanol including those of pure liquids were measured over the entire mole fraction range at five different temperatures (303.15, 308.15, 313.15, 318.15, and 323.15) K. From these experimentally determined values, various thermo-acoustic parameters such as excess isentropic compressibility $ \left( {K_{\text{s}}^{\text{E}} } \right) $ , excess molar volume (V E) and excess free length $ \left( {L_{\text{f}}^{\text{E}} } \right) $ , excess Gibb’s free energy (ΔG *E), and excess enthalpy (H E) have been calculated. The excess functions have been fitted to the Redlich–Kister type polynomial equation. The deviations for excess thermo-acoustic parameters have been explained on the basis of the intermolecular interactions present in these binary mixtures. The theoretical values of speed of sound in the mixtures have been evaluated using various theories and have been compared with experimentally determined speed of sound values in order to check the applicability of such theories to the liquid mixture systems under study. Viscosity data have been used to test the applicability of standard viscosity models of Grunberg–Nissan, Hind–Mc Laughlin, Katti–Chaudhary, Heric and Brewer, Frenkel, Tamura and Kurata at various temperatures for the binary liquid systems under study. 相似文献
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2-Aminopyridinium ions were found to activate nitroalkenes toward conjugate addition of heteroaromatic compounds with low catalyst loadings and the Diels-Alder reaction with the periselectivity opposite to that observed with metal Lewis acids, raising the possibility that a 2-aminopyridinium core might be a promising catalaphore for the asymmetric catalyst design. 相似文献
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Summary It is shown that gamma random variables satisfy a certain factorisation property. Using this property, Goldie's result on mixtures of the exponential distributions is extended. The note also establishes that the generalized inverse Gaussian distribution and the generalized hyperbolic distribution considered by Barndorff-Nielsen and Halgreen (1977) are indeed self-decomposable. 相似文献
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The dielectric relaxation studies on polar binary mixtures of N-methyl aniline with, alcohols, propan-1-ol and isopropyl alcohol have been carried out, at different temperatures and mole
fractions, using — LF impedance analyzer, Plunger method and Abbe’s refractometer in radio, microwave and optic frequency
regions respectively. Kirkwood effective correlation factor, corrective Kirkwood correlation factor, Bruggeman parameter,
relaxation time and thermodynamical parameters are calculated using the experimental data. Conformational analysis of the
formation of hydrogen bond in the equi molar binary mixture systems of N-methyl aniline with propan-1-ol and isopropyl alcohol is supported by experimental and theoretical FT-IR values. 相似文献
28.
S. Sreehari Sastry K. Mallika T. Vishwam S. Lakshminarayana Ha Sie Tiong 《Liquid crystals》2013,40(4):558-571
This paper demonstrated the image analysis technique for the investigation of electro-optic behaviour of homogeneously aligned nematic liquid crystals p-n alkyl benzoic acids (nBA) where n = 5 and 6 under the application of direct current (DC) electric field. Textures of the liquid crystals in the mesophase region of particular temperature were recorded in three monochromatic image planes at the wavelengths of 635 (red), 530 (green) and 475 nm (blue) as a function of applied DC voltage. Electro-optic properties such as transmittance, birefringence, phase retardation and contrast ratio were measured by analysing the optical intensities of the recorded textures using MATLAB software. The changes in the textural features and formation of new textures as a function of voltage provided information for better understanding of the electro-optic characteristics of liquid crystals. Results of this study were compared with the data of the other standard techniques: laser source (633 nm) experiment and United Detector Technology (UDT) sensor of model UV- 35P silicon photo diode which uses white light as source and filters the wavelengths using three colour filters of wavelengths 635, 530 and 475nm. 相似文献
29.
Conformational studies of intermolecular hydorgen bonding through induced crystal G phase in nBA:7HB
S. Sreehari Sastry C. Nageswara Rao T. Vishwam K. Mallika Ha Sie Tiong 《Liquid crystals》2013,40(7):932-941
This paper exploits the physical investigation on liquid crystal complexes obtained by self-organisation of p-n-alkyl benzoic acid (nBA) mesogens with non-mesogenic materials heptyl p-hydroxy benzoate (7HB). Intermolecular interactions of the molecules result the hydrogen bond between the proton donor (COOH) of nBA and proton acceptor (OH) of 7HB. The formation of hydrogen bond is attributed to the quenching of the nematic phase and inducement of crystal G phase in liquid crystal complex. A comparative study of phase abundance is presented with respect to the pure nBAs and other hydrogen bonded liquid crystal complexes of nBAs. Thermal and phase behaviour of the complexes are determined by polarising optical microscope (POM), differential scanning calorimetry (DSC) and image moments approach. Intermolecular interactions which result the hydrogen bond in complexes are investigated using Fourier transform infrared (FTIR) spectroscopy. Molecular structure of the liquid crystal complexes in the solid phase was elucidated using powder X-ray diffraction and proton nuclear magnetic resonance (1HNMR). 相似文献
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Sreehari Surendran Rajasree Jierui Yu Dr. H. Christopher Fry Ryther Anderson Dr. Wenqian Xu Riya Krishnan Jiaxin Duan Dr. Subhadip Goswami Prof. Dr. Diego A. Gómez-Gualdrón Prof. Dr. Pravas Deria 《Angewandte Chemie (International ed. in English)》2023,62(38):e202305323
High quantum yield triplets, populated by initially prepared excited singlets, are desired for various energy conversion schemes in solid working compositions like porous MOFs. However, a large disparity in the distribution of the excitonic center of mass, singlet-triplet intersystem crossing (ISC) in such assemblies is inhibited, so much so that a carboxy-coordinated zirconium heavy metal ion cannot effectively facilitate the ISC through spin-orbit coupling. Circumventing this sluggish ISC, singlet fission (SF) is explored as a viable route to generating triplets in solution-stable MOFs. Efficient SF is achieved through a high degree of interchromophoric coupling that facilitates electron super-exchange to generate triplet pairs. Here we show that a predesigned chromophoric linker with extremely poor ISC efficiency (kISC) but form triplets in MOF in contrast to the frameworks that are built from linkers with sizable kISC but . This work opens a new photophysical and photochemical avenue in MOF chemistry and utility in energy conversion schemes. 相似文献