The surprisingly facile thermal dehalogenation of chlorinated aromatics by a hydroaromatic donor solvent. Tautomerization of chlorinated phenols and anilines

Up to 600 K, chlorinated benzenes and naphthalenes are inert in a hydrogen atom donating solvent such as 9,10-dihydroanthracene. However, when a hydroxyl or amine group is attached to the 2 or 4 position relative to chlorine, a surprisingly facile and selective hydrodehalogenation occurs at temperatures between 530 and 630 K. These features are the result of the onset of tautomeric equilibria for the chlorophenols or -anilines, creating the corresponding enones or imines, respectively, as reactive intermediates. The mechanism of dehalogenation involves the rate-determining transfer of a hydrogen atom from the solvent to the reactive intermediate according to a reverse radical disproportionation (RRD), followed by elimination of chlorine. The reactivity of mono- and dichlorophenols, chloroanilines, 4-chloro-1-naphthol, and 4-chloro-1-naphthylamine dissolved in 9,10-dihydroanthracene has been investigated. By means of density functional theory (DFT) calculations, the energies for the tautomers and their hydrogen affinities have been established. The experimental selectivities could be adequately reproduced by the computed data.     

The fragmentation of some alkyl thio-phosphate esters by electron-impact

The mass spectra of the following compounds have been studied: and the fragmentation pathways established with the aid of accurate mass measurements, metastable transition and appearance potential determination. The mass spectra show that the sulphur-containing compounds (II to IV) give a stronger molecular ion that that of compound I. A further significant difference is the low intensity, in the mass spectra of II to IV, of the fragments relative to the processes that occur in I, probably because the electron removed upon ionisation belongs to the sulpher atom in compounds II to IV and to the oxygen in compound I. The isomeric compounds, (III and IV) show quite different mass spectra, The radicals containing only Phosphorus and oxygen have an ionisation potential close to 9 eV and the presence of sulphur considerably lowes this value. The measured ionisation potentials of compounds I to IV are respectively, 10·7₀, 9·5₅, 9·2₀ and 9·0₀eV. The heats of formation of compounds II and III have been estimated as ?176 and ?118 Kcal mole^?1, respectively.     

Synthesis of a bifunctional monophosphinic acid DOTA analogue ligand and its lanthanide(III) complexes. A gadolinium(III) complex endowed with an optimal water exchange rate for MRI applications

A new bifunctional octa-coordinating ligand containing an aminobenzyl moiety, DO3APABn (H4DO3APABn = 1,4,7,10-tetraazacyclododecane-4,7,10-triacetic-1-{methyl[(4-aminophenyl)methyl]phosphinic acid}), has been synthesized. Its lanthanide(III) complexes contain one water molecule in the first coordination sphere. The high-resolution 1H and 31P spectra of [Eu(H2O) (DO3APABn)]- show that the twisted square-antiprismatic form of the complexes is more abundant in respect to the corresponding Eu(III)-DOTA complex. The 1H NMRD and variable-temperature 17O relaxation measurements of [Gd(H2O)(DO3APABn)]- show that the water residence time is short (298tauM = 16 ns) and falls into the optimal range predicted by theory for the attainment of high relaxivities once this complex would be endowed by a slow tumbling rate. The relaxivity (298r1 = 6.7 mM(-1) s(-1) at 10 MHz) is higher than expected as a consequence of a significant contribution from the second hydration sphere. These results prompt the use of [Gd(H2O)(DO3APABn)]- as a building block for the set-up of highly efficient macromolecular MRI contrast agents.     

Synthesis of pinacol esters of 1‐alkyl‐1H‐pyrazol‐5‐yl‐ and 1‐alkyl‐1H‐pyrazol‐4‐ylboronic acids

Starting from 1H‐pyrazol, a wide number of 1‐alkyl‐1H‐pyrazol‐4‐yl and 1‐alkyl‐1H‐pyrazol‐5‐ylboronic acids and their pinacol esters were synthesized and characterized. The key step in the described methodology is the regioselective lithiation of the pyrazole ring. The synthesized pinacolates are stable under prolonged storage and can be used as convenient reagents in organic synthesis.     

Identification and Quantification of Intrinsic Optical Contrast for Near-infrared Mammography

Near-infrared spectroscopy has been used to quantify the composition of healthy female breast tissue in vivo . By collecting transillumination spectra in the wavelength range 680–1100 nm at 7–9 positions on the breasts of five female volunteers, an attempt was made to quantify the intra- and intersubject variability of breast composition. The dominant absorbers are water, lipids and hemoglobin. Hemoglobin concentration in the breast is substantially lower than that in the brain or muscle (less than 10 μ M ). The measured deoxyhemoglobin concentration can vary by up to 100% between different positions on the same breast. Water and lipid concentrations can show similar variability. Phantom and simulation studies demonstrate that this variability is not due to the effects of tissue boundaries on the measurements. The low hemoglobin concentration implies that optical breast imaging should be performed at wavelengths below about 850 nm to ensure that the image contrast comes predominantly from hemoglobin. Intrasubject variability could have implications for the ability of optical imaging to discern tumors from background contrast variations.     

Removal of tetramethyl ammonium hydroxide from synthetic liquid wastes of electronic industry through micellar enhanced ultrafiltration

In this paper, the separation of tetramethyl ammonium hydroxide (TMAH) from synthetic liquid wastes of electronic industry is carried out by using a micellar enhanced ultrafiltration (MEUF) process. This treatment represents the first step of an integrated process, aimed at the recovery of TMAH and surfactant and water reuse. The laboratory tests are carried out with an ultrafiltration module using initial solutions having a concentration of pollutant equal to 2?g/L and by adding sodium dodecyl sulfate as a surfactant, at a concentration in the range 4–10?mM/L, that is, under and above its critical micellar concentration (CMC). The experiments have been carried out at a fixed temperature of 25°C. The obtained results showed that very good percentage removals of TMAH are achieved (99%), especially when the surfactant was above the CMC.