Transformations of ortho-quinones in the γ-radiolysis of their solutions in cyclohexane

The transformations of 4-tert-butyl-1,2-benzoquinone (I), 3,5-di-tert-butyl-1,2-benzoquinone (II), and 4-methoxy-5-tert-butyl-1,2-benzoquinone (III) in deaerated cyclohexane solutions under exposure to γ-radiation were studied. It was found by chromatography-mass spectrometry and ¹H and ¹³C NMR spectroscopy that the addition of cyclohexyl radicals at the C=O bond in compounds I–III resulted in monoalkyl ethers, whereas cyclic ketal XXI was also formed in the case of compound II. Moreover, quinone I afforded mixed O-and C-alkylation products, and the adduct of cyclohexyl radicals and quinone II at the C=C bond was the source of dimeric products.     

Origin of Aldehydes in Sediments of Qinghai Lake

This paper has analysed the aldehyde fractions in sediments and living organisms of Qinghai Lake using GC-MS and discussed their origin, n-Aldehydes detected in the sediments ranged from C_(16) to C_(32) with a maximum at C_(22) C_(24) or C_(26) and showed a strong even over odd predominance. n-Aldehydes in the living organisms analysed ranged from C_(16) to C_(32) with a maximum at C_(26) or C_(28). The authors believed that aldehydes in modern sediments may directly derive from biosynthesis.     

Origin of Ketones in Sediments of Qinghai Lake

This paper analysed the ketone fractions in sediments and living organisms of Qinghai Lake using GC-MS and discussed their origin,n-Alkan-2-ones detected in the sediments ranged from C_(12) to C_(33) with a maximum at n-C_(25) or n-C_(29) and showed a strong odd predominance, n-Alkan-2-ones in the living organisms analysed ranged from C_(15) to C_(31) with a maximum at n-C_(27).The authors believed that ketones in modern sediments may directly derive from biosynthesis.     

Acidichromism of indolinospirooxazines in isopropanol

1,3,3-tnmethyl-spiro[mdolino-2,3'-[2H]naphtho[2,1-b] [1,4]oxazine(SP1) and 1,3,3-trimen-thyl-9-methoxy-spiro[indolino2,3'-[2H]naphtho[2,1-b] [ 1,4]oxazine] (SP2) react with hydrochloric acid to form the complex SP HCl in isopropanol solution at room temperature The absorption maxima of these complexes are 440 and 463 nm respectively In acidic media,the opening form of spirooxazine can react with hydrochloric acid to form the complex PMC HCl via zwittenon form The absorption spectra of PMC HCl are obviously hypsochromic shifted compared with the reported spectra of the complex in neutral media In the mean time,the thermal stability of the complex is increased.The first order kinetics for the decoloration process of the acidichromic product of the opening form was determined and the lifetimes of these products are 180 and 200 s,respectively.     

Advances of Chromatography in Analysis of Complex Samples

The separation and identification of complex samples is an urgent task that analytical chemistry has to face. Chromatography, as an important analysis technique, has been widely applied to many fields, such as life science, environment, medicine, food and petrochemical engineering.Recently, with the progress of science and tech-     

Role of Regulatory Peptide in Pathogenesis of Shock

The present study evaluated the pathogenetic roles of three kinds of regulatory peptide. The results showed that (i) plasma endothelin(ET) level elevated significantly in septic shock rats, persistent intravenous drip of low doses ET caused development of shock state in normal rats and the irreversible outcome of light hemorrhagic shock. Furthermore, i. v. administration of specific ET-antiserum was significantly effective to septic shock rats, (Ⅱ) Plasma calcitonin gene-related peptide (CGRP) increased by 260% in septic shock rats, i. v. drip of low doses CGRP both in early and late sepsis were effective to shock rats, (Ⅱi) An-giotensin-Ⅱ (ANG-Ⅱ) contents of heart and aorta increased dramatically both in early and late septic shock, and inhibiting its increase with Captopril in late sepsis significantly improved the shock state, but results were inverse in early sepsis. It could be concluded that ET was one of the most important factors participating in the pathogenesis of shock, CGRP had a compens     

The Role of Acetylcholine in the Cognitive Function of Frontal Neurons in Monkeys

To study the role of acetylcholine(ACh) in the cognitive function of frontal lobes, ACh and atropine were applied iontophoretically to the task-related neurons recorded from an area around the superior ramus of arcuate sulcus in the frontal cortex of 4 rhesus monkeys during the performance of two tasks. The spontaneous discharges and taskrelated responses of most of the neurons which increased their discharge rate in the delay and differentiation periods of the discrimination response go/no-go task and in the cue and delay periods of the delayed discrimination go/no-go task, were further increased during the application of ACh and suppressed during atropine. These results suggest that ACh may be involved in the excitatory process of the activity of the neurons in the above-mentioned area of frontal cortex to play an important role in the cognitive functions of attention, discrimination and short-term memory.     

Deprotection of Oximes using Iodosobenzene in the Presence of β‐Cyclodextrin in Water

A mild and efficient method for the regeneration of carbonyl compounds from oximes at room temperature in impressive yields has been developed using iodosobenzene/KBr in the presence of β‐cyclodextrin in water.     

Adsorptive stripping voltammetric determination of traces of molybdenum in natural water in the presence ofα-benzoinoxime

The electrochemical behavior of the molybdenum complex of -benzoinoxime was investigated using cyclic voltammetry and linear scan voltammetry, after adsorptive accumulation of the complex onto a hanging mercury drop electrode (HMDE). The signal corresponds to the reduction of molybdenum in the complex adsorbed at the HMDE surface. Under optimal conditions, the adsorptive stripping voltammetric procedure gave an extremely low detection limit of 0.1 nM (9.6ng/l) Mo(VI) following stirred accumulation for 5 min at 0.0 V (vs. Ag/AgCl). The reduction cur rent-[Mo(VI)] relationships were linear up to 25 and 100 nM. Repetitive determinations of 10 nM solutions gave relative standard deviations of 2.2 and 3.5%, for 1 and 5-min accumulation periods, respectively. Most of the ions investigated did not interfere with the determination of molybdenum, except for tungsten. Excellent selectivity against copper was observed. The proposed procedure was applied to the direct determination of molybdenum in natural water.     

Importance of the nature of α-substituents in pyrrolidine organocatalysts in asymmetric Michael additions

The fundamental factors contributing toward the stereoselectivity in organocatalyzed asymmetric Michael reaction between aldehydes (propanal and 3-phenyl propanal) and methyl vinyl ketone (MVK) are established by using density functional theory methods. Three of the most commonly employed α-substituted pyrrolidine organocatalysts are examined. Several key stereochemical modes of addition between (i) a model enamine or (ii) pyrrolidine enamines derived from aldehydes and secondary amine to MVK are examined. Among these possibilities, the addition of (E)-enamine to cis-MVK is found to have a lower activation barrier. The stereochemical outcome of the reaction is reported on the basis of the relative energies between pertinent diastereomeric transition states. Moderate selectivity is predicted for the reaction involving pyrrolidine catalysts I and II, which carry relatively less bulky α-substituents dimethylmethoxymethyl and diphenylmethyl, respectively. On the other hand, high selectivity is computed in the case of catalyst III having a sufficiently large α-substituent (diarylmethoxymethyl or diphenylprolinol methyl ether). The enantiomeric excess in the case of 3-phenyl propanal is found to be much higher as compared to that with unsubstituted propanal, suggesting potential for improvement in stereoselectivity by substrate modifications. The computed enantiomeric excess is found to be in reasonable agreement with the reported experimental stereoselectivities. A detailed investigation on the geometries of the crucial transition states reveals that apart from steric interactions between the α-substituent and MVK, various other factors such as orbital interactions and weak stabilizing hydrogen-bonding interactions play a vital role in stereoselectivity. The results serve to establish the importance of cumulative effects of various stabilizing and destabilizing interactions at the transition state as responsible for the stereochemical outcome of the reaction. The limitations of commonly employed qualitative propositions, relying on the steric protection of one of the prochiral faces of enamines offered by the bulky α-substituent, are presented.     

Conformational changes of DNA γ-irradiated in the presence of aliphatic alcohols in solution

The conformational changes of DNA in aqueous solutions containing ethanol and iso- and n-propanol having concentrations of 0–23 wt.% and ionic strength μ = 0.003 NaCl and exposed to γ radiation at doses from 0 Gy to 30 Gy were studied by low-gradient viscosimetry and circular dichroism. The dependence of the specific volume (V _sp) of DNA on the radiation dose changed at different contents of alcohol. There is a critical concentration (C _cr) at which the structure of the mixed solvent is rearranged. The V _sp of DNA decreased as the radiation dose increased at C _alc = 12 wt.% < C _cr and increased at C _alc = 23 wt.% > C _cr. In both cases, the largest V _sp of DNA was observed in water ethanol solutions. The secondary structure of the macromolecule in the systems corresponds to the form. It was shown that the observed conformational changes in irradiated DNA at C _alc < C _cr and C _alc > C _cr could not be explained only by the ability of alcohols to intercept the radicals formed in radiolysis of water.     

Average life of oxygen vacancies of quartz in sediments

Average life of oxygen vacancies of quartz in sediments is estimated by using the ESR(electron spin resonance) signals of E' centers from the thermal activation technique. The experi-mental results show that the second-order kinetics equation is more applicable to the life estima-tion compared with the first order equation. The average life of oxygen vacancies of quartz from4895 to 4908 deep sediments in the Tarim Basin is about 10~(18) a at 27℃.     

Manifestation of the Even–Odd Effect in the Spectral Properties of Solvated Electron and in the Probability of Positronium Formation in Alcohols

A change in the energy E _max of the solvated electron, which corresponds to the maximum intensity of its optical absorption spectrum in the homologous series of alcohols seems to be alternating in character. The effect is retained upon elevation of pressure up to 2 kbar but disappears in alcohols frozen at 77 K. Probably, the effect also holds for amines. The alternating character of variation is also observed for the intensity Y ₁ of the narrow components of the angular spectrum of -photons generated upon positron annihilation in alcohols and normal alkanes. The nature of alternation of E _max is associated with the mutual elimination of electric fields induced by the dipole moments of two neighboring CH₂ groups in each solvent molecule, including also the molecules forming the solvation shell of an excess electron. That fact that the E _max value correlates to Y ₁ led to the conclusion that Y ₁, rather than the intensity I ₃ of the long-lived component of the annihilation time spectrum generally used for the purpose, more adequately characterizes the positronium formation probability.     

“Conjugate” Substitution of Hydrogen in the Methyl Group of Pentabromotoluene in the Presence of Strong Bases

The reactions of pentabromotoluene with i-PrONa or t-BuONa in pyridine give N-(pentabromobenzyl)pyridinium bromide and a mixture of isomeric tetrabromotoluenes. In the presence of bromine or carbon tetrabromide, the reductive debromination is blocked, and the reactions involve exclusively substitution of hydrogen in the methyl group of pentabromotoluene by the pyridinium residue.     

Application of Slow Sweep Oscillographic Chronopo-tentiometry in Test of Occupation Poisoning——Determination of Cadmium in Urine

In classical oscillographic chronopotentiometry, frequency of alternating current Is 50 Hz. It was difficult to overcome charging current so the detection limit was high In oscillographic analysis.     

Photooxidation of carbonyl sulfide in the presence of the typical oxides in atmospheric aerosol

Carbonyl sulfide (COS) is one of the most abun-dant sulfur containing gases in the troposphere andlower stratosphere[1,2]. It is relatively inert in the tro-posphere and can be transported into the stratosphere,where it dissociates under the solar ultravi…     

Effects of inclusion of cetirizine hydrochloride in β-cyclodextrin

Following the preparation of inclusion complex of cetirizine (CTZ) and β-cyclodextrin (β-CD), the compound was investigated to assess the possibility of modifying the physicochemical properties (solubility, release, stability, permeability) of CTZ after complexation that are vital for subsequent formulation studies involving the said complex. Changes in FT-IR/Raman spectra, DSC thermograms and XRD diffractograms confirmed the formation of a CTZ–β-CD system. Hydrophilic interaction chromatography with a DAD detector was employed to determine alterations of the CTZ concentration during studies following complexation. An analysis of a phase-solubility diagram of c_CTZ?=?fc_β-CD indicated a linear rise in the solubility of CTZ as the concentration of β-CD increased. The inclusion of CTZ in a system with β-CD significantly reduced the instability of CTZ in the presence of oxidizing factors. It was also found that regardless of the pH of the acceptor fluids used in the release studies an increase was observed in the concentration of CTZ in CD system compared to its free form. The ability to permeate artificial biological membranes manifested by CTZ after complexation was enhanced as well. In summary, CD has significant potential to mask the bitter taste of CTZ and to counter the instability induced by oxidizing factors.     

Characters of the Plateau of Methanol Increment in Frontal Analysis in Reversed Phase Liquid Chromatography

With insulin methanol-water,and the ion-pairing agent,hydrochloric acid and trifluroacetic acid(TEA),the character of the first plateau(FP)on the elution curve of frontal analysis in reversed phase liquid chromatography(RPLC)was investigated by on-line UV-spectrometry and identified with nuclear magnetic resonance(NMR) spectrometry and mass spectrometry.The profile of the FP is the same as that of a usual elution curve of methanol in frontal analysis(FA).When the insulin concentration was limited to a certain range,the height of the FP was found to be proportional to the insulin concentration in mobile phase and its length companying to shorten,The FP profile on the intersection of two tangents reflects the components of the microstructure in the depth direction of the bonded stationary phase layer and the desorption dynamics of the displaced components.The displaced methanol was quantitatively determined by NMR and on-line UV spectrometries.TFA with high UV absorbance can not be used as an ionpairing agent for the investigation of the FP in RPLC,but if can be used as a good marker to investigate the complicated transfer process of components in the stationary phase in RPLC.A stoichiometric displacement process between solute and solvent was proved to be valid in both usual and FA in RPLC.From the point of view of dynamics of mass transfer, the solutes can only contact to the surface of stationary phase in usual RPLC,while solute can penetrate into it in FA of RPLC.The solvation of insulin in methanol and water solution as an example indicating the usage of the FP in the FA was also investigated in this paper.