Abstract Absorption spectra of 2-Fluoro-4-Bromo, 4-Fluoro-2-Bromo and 2-Fluoro-5-Bromo Toluenes have been investigated in the near ultraviolet region in vapour phase. The band systems correspond to allowed transitions with the most intense bands at 2742.09 Å (36458 cm?1), 2745.96 Å (36406 cm?1) and 2771.74 Å (36068 cm?1) identified as 0,0 transitions in 2-Fluoro-4-Bromo, 4-Fluoro-2-Bromo and 2-Fluoro-5-Bromo Toluenes respectively. The bands in 4-Fluoro-2-Bromo Toluene have been analysed in terms of the ground state fundamental 208 cm?1 and excited state fundamentals 244, 611, 855 and 1211 cm?1 and the bands in 2-Fluoro-4-Bromo and 2-Fluoro-5-Bromo Toluenes are explained in terms of the upper state fundamentals 716, 987 and 1230 cm?1 and 722, 886 and 2130 cm?1 respectively. 相似文献
Abstract The infrared and ultraviolet absorption spectra of toluene-d have been investigated for the first time in the regions 400 - 4000 cm?1 and 2350 ?2750 A° respectively. The intense band at 2666.3 A°(37494 cm?1) in the u.v. vapour absorption spectrum has been identified as the o,o band and others have been interpreted in terms of the three (519,632 and 785 cm?1) ground state and the six (454,526,743,935,963 and 1180 cm?1 excited state fundamentals. The correlation of the various frequencies of the ground and excited states of toluene and toluene-d has been done. The observed isotopic shift for toluene-d is 14 cm?1. 相似文献
We investigate the origins of ‘de Vries-like’ liquid crystalline behaviour by introducing an ethynyl spacer in the core of the tricarbosilane-terminated 5-phenylpyrimidine mesogens QL16-6 and QL17-6. The rationale for this structural change is based on the assumption that an ethynyl spacer would create more free volume in the core sub-layer and therefore decrease the orientational order parameter S2 in the SmA phase. The tricarbosilane-terminated mesogens WL41-5 and WL42-6 with a 5-(phenylethynyl)pyrimidine core in either a normal or inverted orientation were synthesised, and their mesomorphic and ‘de Vries-like’ properties characterised using polarised optical microscopy, differential scanning calorimetry, birefringence measurements, small–angle (SAXS) and 2D X-ray scattering. Reduction factors R derived from SAXS and optical tilt angle measurements suggest that neither WL41-5 (R = 0.49) nor WL42-6 (R = 0.80) exhibit ‘de Vries-like’ properties. The S2(T) profiles show an increase in orientational order with decreasing temperature and a sharp discontinuity at the SmA-SmC transition, which is consistent with ‘de Vries-like’ behaviour. However, the Leff(T) profiles suggest an increase in interdigitation that reduces the positive effect of increasing S2 in compensating for the molecular tilt. 相似文献
Development and characterisation of polyethylene oxide (PEO)-based nanocomposite polymer electrolytes comprising of (PEO-SiO2): NH4SCN is reported. For synthesis of the said electrolyte, polyethylene oxide has been taken as polymer host and NH4SCN as an ionic charge supplier. Sol–gel-derived silica powder of nano dimension has been used as ceramic filler for development
of nanocomposite electrolytes. The maximum conductivity of electrolyte ∼2.0 × 10−6 S/cm is observed for samples containing 30 wt.% silica. The temperature dependence of conductivity seems to follow an Arrhenius-type,
thermally activated process over a limited temperature range. 相似文献
As the application of electrocatalyst continues to expand, envisaging the hidden mechanisms occurring at various length scale affecting the catalytic efficiency became important. To enhance the stability of electrocatalyst and reduce the cost, it is of paramount importance to reveal the active site's dynamics (using in situ techniques for getting the real-time information) which directly affect the reactions such as oxygen evolution reaction, hydrogen evolution reaction, and so on. Since such reactions are crucial for many engineering and scientific applications, in situ characterization techniques are required, which could capture such reactions happening at a different length and time scale. This article analyzes the recent progress made in the field of electrocatalyst's characterization using in situ neutron techniques. The article also paves the future path and has delineated the future challenges involved in multiscale correlative techniques (e.g., neutron techniques in the combination of synchrotron or microscopic techniques) used for getting the multiscale (atomic to micrometer range) mechanistic information about the electrocatalyst's working and degradation. 相似文献
Design and synthesis of novel series of 1,3,4-oxadiazoles containing FQs derivatives and screened their antibacterial, antimycobacterial properties. The synthesized compounds were characterized by different spectral techniques like IR, 1H NMR, 13C NMR, mass and elemental analysis. The results of the antimicrobial activity and compounds 6d, 6b, 6e, 6f and 6a demonstrated potent antibacterial activities with zone of inhibition of 42, 36, 37, 34 and 30 mm against S. aureus, E. faecalis, S. pneumoniae, E. coli and K. pneumoniae, respectively. 1,3,4-Oxadiazole derivatives 6a, 6b, 6 g were showed excellent antimycobacterial activity against M. smegmatis H37Rv with MICs 22.35, 16.20, 20.28 µg/mL, respectively. FQs 6d and 6b exhibited highest hydrogen bonding interactions with Asp83 (3.11 A?), Ser80 (2.15 A?) Asp27 (σ-σ), Arg87 (Π-Π), Arg87 (Π-Π), Ser80 (σ-σ), Ala84 (σ-σ) and binding energies ΔG?=????6.41, ??6.97 kcal/mol with active site of topoisomerase-IV from S. pneumoniae [4KPE]. We performed a computational investigation of compounds 6a–j for their absorption, distribution, metabolism and excretion (ADME) properties by using the Molinspiration, Molsoft toolkits. The ligands 6f, 6d and 6b reveal the highest pharmacokinetic properties and possess maximum drug-likeness model score 1.59, 1.46 and 1.23, respectively.
The use of dimedone in green chemistry has been described for the synthesis of selective heterocyclic motifs which are both pharmacologically and industrially important. The objective of this review is to summarize some of the selected recent advances of dimedone in the synthesis of organic compounds utilizing green chemistry procedures. 相似文献
Claudins are proteins that are selectively expressed at tight junctions (TJs) of epithelial cells where they play a central role in regulating paracellular permeability of solutes across epithelia. However, the role of claudins in intercellular adhesion and the mechanism by which they regulate the diffusion of solutes are poorly understood. Here, using single molecule force spectroscopy, the kinetic properties and adhesion strength of homophilic claudin-1 interactions were probed at the single-molecule level. Within the range of tested loading rates (10(3)-10(5) pN/s), our results showed that homophilic claudin-1 interactions have a reactive compliance of 0.363 +/- 0.061 nm and an unstressed dissociation rate of 1.351 +/- 1.312 s-1. This is more than 100-fold greater than that of E-cadherin. The weak and short-lived interactions between claudin-1 molecules make them highly unstable and dynamic in nature. Such a dynamic interaction is consistent with a model where breaking and resealing of TJ strands regulate the paracellular diffusion of solutes. 相似文献
Four bacteria, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus warneri, and Micrococcus luteus, were grown at temperatures of 23, 30, and 37 degrees C and were characterized by pyrolysis-gas chromatography/differential mobility spectrometry (Py-GC/DMS) providing, with replicates, 120 data sets of retention time, compensation voltage, and ion intensity, each for negative and positive polarity. Principal component analysis (PCA) for 96 of these data sets exhibited clusters by temperature of culture growth and not by genus. Analysis of variance was used to isolate the constituents with dependences on growth temperature. When these were subtracted from the data sets, Fisher ratios with PCA resulted in four clusters according to genus at all temperatures for ions in each polarity. Comparable results were obtained from unsupervised PCA with 24 of the original data sets. The ions with taxonomic features were reconstructed into 3D plots of retention time, compensation voltage, and Fisher ratio and were matched, through GC-mass spectrometry (MS), with chemical standards attributed to the thermal decomposition of proteins and lipid A. Results for negative ions provided simpler data sets than from positive ions, as anticipated from selectivity of gas phase ion-molecule reactions in air at ambient pressure. 相似文献