Characterisation of a series of acetals/ketals of bis(2-nitrophenyl) ethanediol and bis(4,5-dimethoxy-2-nitrophenyl) ethanediol under APCI mass spectrometric conditions

A series acetals/ketals of aldehydes and ketones formed by the reaction of two photolabile protecting groups, bis(2-nitrophenyl) ethanediol and bis(4,5-dimethoxy-2-nitrophenyl) ethanediol (I and II, respectively), were analysed under EI, LSIMS, ESI and APCI conditions to obtain molecular weights as well as structural information. The EI and LSIMS techniques failed to give molecular weight information. The positive ESI yielded [M + H](+) ions only for I; however, with added Na(+) both I and II formed [M + Na](+) adducts. But upon decomposition, the [M + Na](+) ions yielded Na(+) ion as the only product ion. Similarly, under negative ion ESI conditions both I and II gave molecular weight information by forming adduct ions with halide anions (F(-), Cl(-), Br(-) and I(-)); however, they did not give structural information as they resulted in only the halide anion as the abundant fragment ion upon dissociation. All the compounds formed abundant M(-*) ions under negative ion APCI conditions, and their MS/MS spectra showed characteristic fragment ions; hence the acetals/ketals of I and II could be successfully characterized under negative ion APCI conditions.     

Ion-pair solid-phase extraction and gas chromatography-mass spectrometric determination of acidic hydrolysis products of chemical warfare agents from aqueous samples

The chemical warfare agents (CWA) degrade rapidly in aqueous samples and convert to acidic degradation products. Extraction and identification of the degradation products from complex matrices using simple sample preparation and sensitive detection and identification is the most important step in the off-site analysis of samples. In this present study, we report a simple sample preparation step based on ion-pair (IP) solid-phase extraction (SPE) for the extraction of acidic degradation products of CWA namely methyl, ethyl, propyl phosphonic acids, thiodiglycolic acid and benzilic acid. The analysis was performed on GC-MS in electron impact ionization mode. Three IP reagents triethylamine (TEA), tetrabutylammonium bromide (TBAB) and cetyltrimethyl ammonium bromide (CTAB) were used. The recoveries were estimated using the internal and external standard methods. The recovery of the compounds was almost negligible when TEA was used as IP reagent. The recoveries obtained when TBAB and CTAB were used as IP reagents were high and reproducible. The recovery of test chemicals is above 90%, except for methyl phosphonic acid and ethylphosphonic acid (20.6 +/- 3.2% and 35.8 +/- 2.5%, respectively). The minimum detection limits of the method were calculated for all chemicals in both full scan and selected ion monitoring modes. The test chemicals could be detected in microgram per litre quantities by the IP-SPE method.     

Synthesis of O-spiro-C-aryl glycosides using organocatalysis

An organocatalysis strategy has been developed toward the synthesis of O-spiro-C-aryl glycosides with different configurations in the sugar part. This strategy has been extended to the synthesis of the Papulacandin class of compounds.     

Synthesis, characterization, and antifungal activity of biaryl-based bis(1,2,3-triazoles) using click chemistry

Abstract  

Click chemistry was used to synthesize a series of biaryl-based bis(1,2,3-triazoles). Their antifungal activity was evaluated against three soil-borne plant pathogenic fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and Fusarium oxysporum, using the food poison technique at concentrations of 62.5–500 μg/cm³.     

Nonlinear Effects of a Gaussian Laser Beam on Megagauss Magnetic Field Generation in Laser Produced Plasma

The generation of megagauss magnetic field due to the time dependent part of the ponderomotive force of a self-focused Gaussian laser beam indicent on a plasma has been studied. Defocusing of the laser beam becomes possible due to diffraction divergence in the case of a weakly nonlinear medium. The influence of defocusing of a laser beam on magnetic field generation has also been investigated. It is found that the magnitude of the magnetic field due to self focusing of the beam is enhanced and is comparable with the observed values, while there is a reduction in the magnitude of the magnetic field when the beam defocuses due to diffraction divergence in the presence of weak nonlinearity.     

A Tabulation of Hilbert Transforms for Electrical Engineers

The Hilbert transform has found application in the analysis of single-sideband signals and angle modulation in communication systems. This extensive tabulation of this transform should prove handy for engineers as much as the more popular Laplace transform tabulations. Such a comprehensive listing of Hilbert transforms is not available in any published work so far.     

Reactions between hydroxylamines and aroyl cyanides

Aromatic hydroxylamines and sterically bulky aliphatic hydroxylamines react with aroyl cyanides to give exclusively the $\text{O}$-acyl derivatives.     

Dielectric relaxation of butyl acrylate—alcohol mixtures using time domain reflectometry

Dielectric relaxation measurements of butyl acrylate—alcohol mixtures at different concentrations and temperatures within the frequency range of 10 MHz to 10 GHz have been carried out using time domain reflectometry. Parameters such as the static permittivity, dielectric relaxation time, the Kirkwood correlation factor, the excess inverse relaxation time, and thermodynamic functions were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The value of the dielectric properties decreases with increasing butyl acrylate concentration in alcohol and systematically varies with the length of alcohol alkyl chain. Negative values of the excess inverse relaxation time found for all concentrations and at all temperatures studied may indicate that the effective dipoles rotate slowly.