On the Reaction of 3-Acetyl Coumarin with Alkyl Phosphites. Structural Confirmations Based on X-Ray Crystallography

3-Acetyl coumarin ( 1 ) reacts with dialkyl phosphites at 100°;C for 8 h to give the phosphonates 2 . Under the same experimental conditions, 1 reacts with trialkyl phosphites to form a mixture of the phosphonates 2 and 3 . The molecular structures of these products were elucidated by x-ray crystallography.     

Atmospheric Pressure Photo Ionization Hydrogen/Deuterium Exchange Mass Spectrometry—a Method to Differentiate Isomers by Mass Spectrometry

In this report, a method for in-source hydrogen/deuterium (H/D) exchange at atmospheric pressure is reported. The method was named atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry (APPI HDX MS). H/D exchange was performed by mixing samples dissolved in toluene with CH₃OD solvent and analyzing the mixture using atmospheric pressure photo ionization mass spectrometry (APPI-MS). The APPI HDX spectra obtained with contact times between the analyte solution and methanol-OD (CH₃OD) of?<?0.5 s or 1 h showed the same pattern of H/D exchange. Therefore, it was concluded that APPI HDX occurred in the source but not in the solution. The proposed method does not require a specific type of mass spectrometer and can be performed at atmospheric pressure. H/D exchange can be performed in any laboratory with a mass spectrometer and a commercial APPI source. Using this method, multiple H/D exchanges of aromatic hydrogen and/or H/D exchange of active hydrogen were observed. These results demonstrated that H/D exchange can be used to distinguish between isomers containing primary, secondary, and tertiary amines, as well as pyridine and pyrrole functional groups.

Miscibility Studies of Dextran/Poly(vinyl pyrrolidone) Blend in Solution

The miscibility of dextran (Dex)/poly(vinyl pyrrolidone) (PVP) in solution has been investigated in different percentages of the blend components by employing viscosity, density, refractive index and ultrasonic velocity methods at 30 and 50°C, respectively. Ultrasonic velocity and adiabatic compressibility against blend compositions were plotted and found to be linear. The interaction parameters μ and α have been obtained by using the viscosity data. The results indicated that the Dex/PVP blends are miscible in the entire composition range and it was further confirmed by ultrasonic velocity, density, refractive index studies. In addition, the results revealed that the change in temperature has no significant effect on the miscibility of Dex/PVP polymer blend.     

Identification of wild collected mosquito vectors of diseases using gas chromatography–mass spectrometry in Jazan Province,Saudi Arabia

Thirty‐three species of mosquitoes have been reported from the Kingdom of Saudi Arabia. Several of these mosquitoes, Anopheles gambiae Giles s.l., Anopheles stephensi Liston, Culex pipiens Linnaeus, Culex quinquefasciatus Say, Culex tritaeniorhynchus Giles, Stegomyia aegypti (Linnaeus) and Aedimorphus vexans arabiensis (Patton) are known vectors of human and animal diseases. In this study, the cuticular hydrocarbon profiles of eight mosquito species using gas chromatography–mass spectrometry were analyzed. Wild collected fourth‐instar larvae were reared, and single, newly emerged, unfed adult females were used for the analysis. A total of 146–160 peaks were detected from the cuticular extracts by gas chromatography. Repeated analysis of variance (ANOVA) and Tukey HSD Post Hoc test was used to test for quantitative differences in relative hydrocarbon quantity. In addition, a linear regression model was applied using Enter method to determine the diagnostic peaks for the eight mosquito specimens. The ANOVA test indicated that relative peaks were significant (P < 0.05) when selected pairs of peaks were compared. Also, seven compounds showed qualitative differences among the five mosquito vectors tested. The classes of constituents present were n‐alkanes, monomethylalkanes, dimethylalkanes, trimethylalkanes, alkenes, branched aromatic hydrocarbons, aldehydes and esters. These compounds have a carbon chain length ranging from 8 to 18 carbons. The most abundant compound in all adult mosquito specimens was n‐hexylacrylate [retention time (RT) 6.73 min], which was not detected in Cx. pipiens. In Cx. pipiens, the most abundant peak was benzaldehyde (RT 2.98 min). Gas chromatography–mass spectrometry is a suitable method to identify adult mosquitoes, especially from focal areas of public health concern such as Jazan Province, Saudi Arabia. This method allows a wide range of adult collected material to be identified with high accuracy. Copyright © 2013 John Wiley & Sons, Ltd.     

The effect of crystal structure on the thermal reactivity of CL-20 and its C4-bonded explosives

The critical temperature and mechanism functions for thermal decomposition of ε-CL-20, RS-ε-CL-20, α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 were evaluated based on non-isothermal TG data. A two-step mechanism has been found for thermal decomposition of α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, where the initial step is partly controlled by crystal structure of CL-20. The more reasonable mean activation energies could be obtained after peak separation for each individual steps. In fact, the activation energy for the post integrated process is almost equivalent with that of the second step, indicating that the total activation energy at the main decomposition process is dominated by thermolysis of CL-20 molecular. Besides, it has been found that the decomposition of C4 matrix does not affect the decomposition of normal ε-CL-20, resulting in identical activation energy and reaction model. However, the interaction between the C4 matrix and RS-ε-CL-20 is significant especially at the initial stage, where the activation energy of RS-ε-CL-20/C4 was overestimated before peak separation, while the activation energy for the second step due to thermolysis of CL-20 molecular is underestimated. The first decomposition step for α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 could be considered as autocatalytic process (AC model), whereas the second as JMA model, which is also applicable to that of pure ε-CL-20 and RS-ε-CL-20. Moreover, The critical temperatures of thermal explosion (T _b) are obtained as 205.6, 205.5, 209.4, 214.4, and 227.5 °C for α-CL-20, ε-CL-20, RS-ε-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4, respectively. It proves that the C4 matrix could stabilize ε-CL-20 while the crystal form of CL-20 has little effect on its thermal stability.     

Mechanistic study of quinone-polyalcohol interaction through cyclic voltammetry

The electrochemistry of some quinones has been focused to determine the mode of interaction in presence of polyalcohols. Three compounds of each family (benzoquinones, naphthoquinones and anthraquinones) were investigated through cyclic voltammetry in the presence of ethylene glycol (a diol)) and glycerol (a triol) in dichloromethane and acetonitrile at 25°C. The observed positive shift in both the waves of the quinone with successive addition of alcohol was attributed to hydrogen bonding in the quinone-alcohol couple. “Two electron one step” electron transfer mechanism was proposed for the increase in the first wave height at the expense of second. The depletion of the first anodic wave at higher concentration of polyalcohol was rationalized in terms of protonation-deprotonation mechanism. A prior peak observed in the presence of glycerol was ascribed to the hydrogen bonding of the alcohol with neutral quinone. The difference in basicity strength within a family as well as among the three quinone families was also addressed in view of the interaction effectiveness.     

Biochemical study for the effect of henna (Lawsonia inermis) on Escherichia coli

Leaf samples of Lawsonia inermis (Li) were examined for their antimicrobial potential. Broth extracts in different concentrations were prepared and bioassayed in vitro for the growth of Escherichia coli. The growth of E. coli pathogen was inhibited to various degrees by increasing the concentration of the herbal powder. In addition to the observed alterations which were detected electrophoretically in the protein pattern, were activities of the amylase enzyme and glycoprotein fractions. The protein pattern has one common band of Rf 0.47 and two characteristic bands of Rf 0.36 and Rf 0.42 for E. coli sample. The quantitative mutation was observed in the bacteria with different concentrations of L. inermis compared with the control. Some types of proteins in E. coli completely disappeared upon being S.I affected. The amylase pattern showed one common band with Rf 0.037 and two characteristic bands with Rf 0.18 and Rf 0.37 for E. coli sample. The obvious quantitative mutation observed in bacteria with different concentrations of L. inermis compared with E. coli. The glycoprotein pattern recorded one common band at R₁ with Rf 0.94 for E. coli sample and bacteria inoculated with different concentrations of L. inermis. These results confirmed the antibacterial activity of henna leaves and supported the traditional use of the plant in therapy of bacterial infections and disturbances that occurred at the biochemical level. The broth extract of the L. inermis leaves showed obvious antibacterial activity against E. coli.     

Optical metal-organic framework sensor for selective discrimination of some toxic metal ions in water

This paper reports the development of a facile and effective approach, based on the use of Zr-based metal-organic frameworks (UiO-66) sensor with micropores geometry, shape and particle morphology for the visual detection and removal of ultra-traces of some toxic metal ions such as Bi(III), Zn(II), Pb(II), Hg(II) and Cd(II). UiO-66 was used as selective carriers for accommodating hydrophobic chromophore probes such as dithizone (DZ) without coupling agent for sensitive and selective discrimination of trace level of toxic analytes. The developed UiO-66 sensor was utilized for the detection of ultra-traces of some toxic metal ions with the naked eye. The new sensor displays high sensitivity and selectivity of a wide range of detectable metals analytes up to 10⁻¹⁰ mol dm⁻³ in solution, in a rapid analyte uptake response (seconds). The developed sensor is stable, cost effective, easy to prepare, and would be useful for rapid detection and removal of ultra-traces of toxic metal ions in water samples.     

Synthesis of Some New Spiro Heterocycles from the Reaction of Cycloalkylidenemal Ononitriles with Active Methylene Reagents

The reaction of cycloalkylidenemalononitriles 1a–c with some active methylene reagents as well as cycloalkanones in boiling ethanol containing piperidine catalyst affords a series of new spiro heterocyclic systems.