Synthetic routes to cyclopropylidenecarbinols and to cyclopropylidienes

Functionalized alkylidine cyclopropanes have beeen prepared from 1-seleno 1-vinyl cyclopropanes using [2,3] sigmatropic rearrangement of their corresponding selenonium ylides. A comparison with sulphur analogues is presented.     

Kinetics of competitive addition of methyldichlorosilane to 1-hexene and to acetone

The competitive addition of methyldichlorosilane (MDChS) to 1-hexene and acetone^** has been studied. The estimated relative constant is effective and depends on acetone concentration and does not obey the Arrhenius temperature equation. A possible explanation is the complexation of methlydichlorosilyl radicals by acetone molecules.

---

, 1- , -, . - .

---

---

Initiated by -irradiation of⁶⁰Co.     

Quantification of doses and health risks to organs and tissues corresponding to different age groups due to radon in water

Journal of Radioanalytical and Nuclear Chemistry - This paper quantifies the inhalation and ingestion doses to different organs and tissues due to radon dissolved in drinking water. For this a...     

Abraham Model Correlations for Transfer of Neutral Molecules to Tetrahydrofuran and to 1,4-Dioxane,and for Transfer of Ions to Tetrahydrofuran

Data have been compiled from the published literature for the partition coefficients of solutes and vapors into anhydrous tetrahydrofuran and 1,4-dioxane. The logarithms of the water-to-ether partition coefficients, log₁₀ P, and gas-to-ether partition coefficients, log₁₀ K, were correlated with the Abraham solvation parameter model. The derived correlations described the observed log₁₀ P and log₁₀ K values for both ether solvents to within average standard deviations of 0.16 log₁₀ units or less. The log₁₀ P correlation for tetrahydrofuran was extended to include the partition of ions by inclusion of a cation-solvent and an anion-solvent term.     

Ene reactions of olefins,part II. The addition of ethylene to propylene and to isobutene and the addition of propylene to propylene

The pyrolysis of ethylene–propylene and ethylene–isobutene mixtures has been studied in a static system over the temperature range of 682°–754° K and for initial pressures of each olefin of 33–300 torr. The following molecular ene reactions were observed and the rate constants measured: Using thermodynamic data, rate constants for the corresponding retro-ene decomposition reactions were calculated and compared to kinetic data reported for similar compounds. Other products were formed by radical chain processes, the main higher molecular weight ones being cyclopentene and 1-methylcyclopentene. A mechanism involving addition of allyl radicals is suggested for the formation of these products.     

Combining Experimental and Computational Studies to Understand and Predict Reactivities of Relevance to Homogeneous Catalysis

This article showcases three major uses of computational chemistry in reactivity studies: the application after, in combination with, and before experiment. Following a brief introduction of suitable computational tools, challenges and opportunities in the implementation of computational chemistry in reactivity studies are discussed, exemplified with selected case studies from our and other laboratories.     

Reduction of temazepam to diazepam and lorazepam to delorazepam during enzymatic hydrolysis

It has been previously reported that treatment of urinary oxazepam by commercial β-glucuronidase enzyme preparations, from Escherichia coli, Helix pomatia and Patella vulgata, results in production of nordiazepam (desmethyldiazepam) artefact. In this study, we report that this unusual reductive transformation also occurs in other benzodiazepines with a hydroxyl group at the C3 position such as temazepam and lorazepam. As determined by liquid chromatography-mass spectrometry analysis, all three enzyme preparations were found capable of converting urinary temazepam into diazepam following enzymatic incubation and subsequent liquid–liquid extraction procedures. For example, when H. pomatia enzymes were used with incubation conditions of 18 h and 50 °C, the percentage conversion, although small, was significant—approximately 1% (0.59–1.54%) in both patient and spiked blank urines. Similarly, using H. pomatia enzyme under these incubation conditions, a reductive transformation of urinary lorazepam into delorazepam (chlordesmethyldiazepam) occurred. These findings have both clinical and forensic implications. Detection of diazepam or delorazepam in biological samples following enzyme treatment should be interpreted with care.     

Gas phase acidities of CH bonds adjacent to oxygen and to sulphur

It has been shown, by double zeta quality ab initio MO calculations, that, in the gas phase, a CH bond adjacent to sulphur is more acidic than a CH bond adjacent to oxygen. This trend is in agreement with experimental observations in solution.     

A convenient conversion of indoles to 3,3-dibromooxindoles and then to isatins

3-Bromoindoles, 3-unsubstituted indoles, or 3-formylindoles on treatment with NBS (2,3, or 4 molar equivalents, respectively) in $\text{t}$-butanol give 3,3-dibromooxindoles, and these readily yield the corresponding isatins on hydrolysis.     

Pre-irradiation of surfactants to enhance their capacity to solubilise drugs and dyes

The present work has used pre-irradiation of surfactants in order to enhance their capacity to solubilize hydrophobic drugs and dyes. Aqueous solution of two pluronic surfactants viz., F-127 and P-123 were subjected to gamma radiation. These irradiated surfactant solutions were used to solubilize five drugs such as ornidazole, tinidazole, ciprofloxacin, aceclofenac, and methylparaben, and two dyes, methyl orange and eosin yellow. Their capacity for enhancing solubilisation was compared with that of unirradiated surfactants. The irradiated surfactant solutions displayed 0.88%–31.9% higher solubilisation compared to unirradiated surfactant solutions. This phenomenon of enhancement in solubility is explained through changes in the physical properties like decreased surface tension and increased hydrodynamic radius in irradiated block polymeric surfactants. Irradiation of surfactants for enhancing their capacity to solubilize hydrophobic chemical entities has been used for the first time.     

Unexpected transformation of quinones to spirolactones and to naturally occurring naphthalenic compounds

In the last few years, natural quinones of the lapachol group have been used as starting points for the preparation of several bioactive heterocyclic compounds. Herein, we announce that lapachones, derivatives of lapachol, under certain conditions in the presence of inorganic reagents give unexpected products, spirolactones and naphthalenic derivatives, nordihydrolapachenone and tetrahydrotectol, both naturally occurring compounds. Nordihydrolapachenone was identified by X-ray analysis. Lapachol itself can also be converted to tetrahydrotectol.     

Application of arsenite reduction to the potentiometric determination of gold and to the analysis of mixtures and alloys

The present work is an application of iodide to the reduction of gold(III), in an attempt to develop new method for gold(III) based on potentiometric back-titration of the excess of iodide with mercury(II). Although it was proved by calculation that the reduction of tetrachloroaurate to the metal should proceed quantitatively to completion, yet our experiments showed that the reduction under ordinary conditions, gave Au(I) in the form of a white precipitate of AuI. We succeeded to push the reduction with iodide to the metal by an excess of ethanol-ether catalyzed iodide at somewhat elevated temperature.With the experimental conditions established a reliable procedure have been developed involving a potentiometric finish which enabled accurate determination of gold(III), either alone or in some of its alloys.     

Analytical challenges and the development of biomarkers to measure and to monitor the effects of ocean acidification

Changing ocean-carbonate chemistry caused by oceanic uptake of anthropogenic atmospheric carbon dioxide leads to the formation of carbonic acid, thus lowering the pH of the sea with predictions of a decrease from current levels at 8.15 to 7.82 by the end of the century. The exact measurement of subtle pH changes in seawater over time presents significant analytical challenges, as the equilibrium constants are governed by water temperature and pressure, salinity effects, and the existence of other ionic species in seawater.Here, we review these challenges and how pH also affects dissolved inorganic and organic chemicals that affect biological systems. This includes toxic compounds (xenobiotics) as well as chemicals that are beneficial for marine organisms, such as the chemical signals (i.e. pheromones) that are utilized to coordinate animal behavior. We review how combining analytical, molecular and biochemical tools can lead to the development of biosensors to detect pH effects to enable predictive modeling of the ecological consequences of ocean acidification.     

A General Introduction to SCTA and to Rate-Controlled SCTA

Journal of Thermal Analysis and Calorimetry -