Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

Critical evaluation of spiking of low-grade ore samples in activation analysis for gold and uranium

In applying non-destructive neutron-activation analysis for gold and uranium in spiked low-grade ore samples, the following extrapolated unspiked concentrations were measured: 0.27₈ ± 0.01₅ ppm gold (chemical assay: 0.20₂ ± 0.02₀ ppm gold); 25.1 ± 1.1 ppm uranium (chemical assay value: 19.5 ±2.0 ppm uranium). Different approaches to the fitting of results, and the influence of spiking non-uniformity, are discussed.     

Nitration of furan derivatives with acetyl nitrate

The mixture of products formed in the nitration of methyl furan-2-carboxylate in acetic anhydride was separated by means of thin-layer and column chromatography. It was found that products of cis and trans addition of acetyl nitrate to the furan ring — methyl 5-nitro-2-ace-toxy-2,5-dihydrofuran-2-carboxylate and 5-nitro-4-acetoxy-4,5-dihydrofuran-2-carboxylate — and methyl 5-nitrofuran-2-carboxylate are formed in the nitration.     

Synthesis in the fields of 5-nitrofuryl-2-polyalkenals and 5-nitrofuryl-2-polyalkenones. VII. Synthesis and investigation of the antibacterial properties of derivatives of α,β-unsaturated and polyene aldehydes and ketones of the 5-nitrofuran series

Antibacterial properties and toxicities were determined for 66 compounds of the 5-nitrofuran type to ascertain the connection between structure and biological activity.Unsaturated 5-nitrofuran aldehydes and some of their simplest derivatives (acetals, acylals) have high antibacterial activity and a broad spectrum. However, these compounds cannot be used in medicine because of their appreciable toxicities and low stabilities. One of the ,-unsaturated ketones in this series, 5-nitrofurfurylideneacetone, has a broad antibacterial spectrum combined with lower toxicity. Low-toxicity derivatives of 1-aminohydantoin and 3-amino-2-oxazolid-2-one are among the imino derivatives of high antibacterial activity investigated.For Part VI see [1].     

New SERS feature of β‐carotene: consequences for quantitative SERS analysis

While recording SERS spectra of pure β‐carotene at sub‐micromole concentrations for reference purpose, we discovered an unusual spectral response never reported before. In pre‐resonance conditions with the 532‐nm line, SERS of β‐carotene with AgNPs exhibits among the strong υ(CC) mode at 1512 cm⁻¹ unshifted from normal Raman spectrum, additional strong bands at 1649, 1575 and 1387 cm⁻¹ as well as other medium bands not observed in the Raman spectrum of the crystalline powder. Such behavior is explained in terms of selection rules relaxation upon cyclohexene terminal rings of the β‐carotene interaction with the NP surface. AFM images of the SERS system suggested dimers and trimers clustering of the nanoparticles with adsorbed β‐carotene. In light of the new SERS feature the consequences in correct interpretation of the SERS imaging from complex biosystems containing carotenoids are discussed. Relative intensity ratio of the β‐carotene band at 1512 cm⁻¹ and water against concentration allowed a reliable SERS calibration curve for 50 to 500 nmol l⁻¹ concentration range and provided quantitative SERS assessment of the carotenoid content in the sea urchin (Paracentrotus lividus) gonads extracts. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrical characterization of deep levels in n-type GaAs after hydrogen plasma treatment

Deep level transient spectroscopy (DLTS) and Laplace-DLTS (L-DLTS) have been used to investigate defects in an n-type GaAs before and after exposure to a dc hydrogen plasma (hydrogenation). DLTS revealed the presence of three prominent electron traps in the material in the temperature range 20-300 K. However, L-DLTS with its higher resolution enabled the splitting of two narrowly spaced emission rates. Consequently four electron traps at, E_C—0.33 eV, E_C—0.36 eV, E_C—0.38 eV and E_C—0.56 eV were observed in the control sample. Following hydrogenation, all these traps were passivated with a new complex (presumably the M3), emerging at E_C—0.58 eV. Isochronal annealing of the passivated material between 50 and 300 °C, revealed the emergence of a secondary defect, not previously observed, at E_C—0.37 eV. Finally, the effect of hydrogen passivation is completely reversed upon annealing at 300 °C, as all the defects originally observed in the reference sample were recovered.