Summary We have found that sodium vanadate oxidises hydroxylamine quantitatively and rapidly to nitrous oxide, even at the room temperature, if the reaction is carried out in 5–6 N hydrochloric acid medium using copper sulphate as catalyst.One of the authors, K.Bhaskara Rao, desires to thank the Ministry of Education, Government of India, for the award of a ResearchScholarship, and the authorities of the Andhra University for providing the research facilities.See also Z. analyt. Chem.156, 180 (1957). 相似文献
Simple pulse-acquire NMR methods are presented for accurate quantitation of calcium (Ca(2+)), magnesium (Mg(2+)) and sodium (Na(+)) in human serum. Ca(2+) and Mg(2+) can be determined simultaneously by (1)H NMR via their EDTA (ethylenediaminetetraacetic acid) complexes. Spectra are acquired before and after addition of EDTA, and the difference spectrum is used for integration of the signals from the complexes relative to an internal reference. Serum sodium can also be determined through pulse-acquire (23)Na NMR by integration of the free sodium signal relative to a reference signal (Na(+)+EDTA in a coaxial capillary tube). The method shows excellent accuracy and precision for all three metal ions. Slow chemical exchange between complexed and free EDTA at the natural pH of serum does not limit the accuracy of the determination of Ca(2+) and Mg(2+), and the large errors associated with spin-echo spectral editing methods are avoided. 相似文献
The title compound is C11H17N4I, F.W.=330.20, monoclinic, space groupP21/a,a=11.586(2),b=10.617(1),c=10.417(1) Å, =94.567(2)°,Z=4,F(000)=652, (MoK)=0.7107 Å, (MoK)=2.31 mm–1,V=1277.31 Å3,DC=1.71 gcm–3,Dm=1.70 gcm–3. The structurewassolved by Patterson and Fourier methods and refined to anR value 0.031 for 1620 observed reflections. The connectivity and conformation of the addition product ofcis-1,5-cyclononadiene and iodine azide was determined by X-ray analysis. The reaction product contains a chair-conformation cyclohexane ring that iscis fused to a cyclopentane ring. The cyclopentane ring has an envelope conformation and an equatorially oriented iodine substituent. A planar tetrazole ring is axially substituted on the cyclohexane ring. The plane of the tetrazole ring makes a dihedral angle of 69.6° with the average plane of the carbon atoms of the cyclohexane ring. 相似文献
This research deals with the inhibition activity of glutathione in 0.5 M HCl on the corrosion behavior of 6061Al-SiC(p) composite. Glutathione is an eco-friendly water-soluble inhibitor. Polarization results reveal the cathodic inhibitor behavior of glutathione (Gt). The inhibition performance of Gt increases by increasing its concentration and lowering the medium temperature. The decrease in the corrosion current density and increase in inhibition efficiency on increasing Gt concentration reveal the attenuation of composite corrosion. Experimental results indicate the mixed adsorption with predominantly physisorption of Gt molecules adsorption on the composite surface following Langmuir adsorption isotherm. The impedance measurements indicate the rise in polarization resistance with an increase in Gt concentration, showing the control of composite corrosion. The surface analysis of the corroded and inhibited composite samples using a scanning electron microscope and atomic force microscope supports Gt molecules’ adsorption. The quantum chemical calculations confirm the conclusions of the experimental studies.
We have discovered that ethylenedioxythiophene (EDOT) can be used as a central unit for the synthesis of bent-core liquid crystals (BC LCs). Two series of EDOT-based BC LCs are prepared via Sonogashira coupling reaction. The mesophase behaviour of all the compounds was characterised using a combination of polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. EDOT-based three-ring compounds were found to be nonliquid crystalline, while all the four derivatives of five-ring series, including a branched alkoxy chain derivative, display enantiotropic nematic phase over wide temperature range. The bent angle of these compounds is about 153°, which falls in between typical rod-like and banana liquid crystals. The transition temperature of branched alkoxy chain compound is lower than straight alkoxy chain compounds. The detailed XRD investigations of all the mesogens corroborate the presence of nematic phase. 相似文献
Penicillin V acylase (PVA), a member of newly evolved Ntn-hydrolase superfamily, is a pharmaceutically important enzyme to produce 6-aminopenicillanic acid. Active site characterization of recently purified monomeric PVA from Rhodotorula aurantiaca (Ra-PVA), the yeast source, showed the involvement of serine and tryptophan in the enzyme activity. Modification of the protein with serine and tryptophan specific reagents such as PMSF and NBS showed partial loss of PVA activity and substrate protection. Ra-PVA was found to be a multi-tryptophan protein exhibiting one tryptophan, in native and, four in its denatured condition. Various solute quenchers and substrate were used to probe the microenvironment of the putative reactive tryptophan through fluorescence quenching. The results obtained indicate that the tryptophan residues of Ra-PVA were largely buried in hydrophobic core of the protein matrix. Quenching of the fluorescence by acrylamide was collisional. Acrylamide was the most effective quencher amongst all the used quenchers, which quenched 71.6% of the total intrinsic fluorescence of the protein, at a very less final concentration of 0.1 M. Surface tryptophan residues were found to have predominantly more electropositively charged amino acids around them, however differentially accessible for ionic quenchers. Denaturation led to shift in λmax from 336, in native state, to 357 nm and more exposed to the solvent, consequently increase in fluorescence quenching with all quenchers. This is an attempt towards the conformational studies of Ra-PVA. 相似文献