Synthesis and fragmentation of new 2‐phosphabicyclo[2.2.2]octene 2‐oxides

The substitution pattern of the 2‐phosphabicyclo[2.2.2]octene framework and the skeleton itself were varied to obtain new cycloadducts usable in phosphorylations and to study their ability to undergo fragmentation. Thus, an N‐methyl and several P‐trialkylphenyl derivatives ( 7 and 9 , respectively) were synthesized, together with two diaza species ( 8 ) whose stereostructure was evaluated by single crystal X‐ray analysis. Mechanistic studies on the UV light‐mediated photolysis of the P‐aryl phosphabicyclooctenes ( 9 ) in the presence of methanol supports the suggestion of a novel addition–elimination reaction path. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:626–632, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10052     

Determination of LogP for Biologically Active Chalcones and Cyclic Chalcone Analogs by RPTLC

JPC – Journal of Planar Chromatography – Modern TLC - LogP values of 41 biologically active chalcones (Figure 1, 1) and their cyclic analogs, E-2-(X-benzylidene)-1-indanones (Figure 1,...     

Modification of D‐glucose‐based 18‐crown‐6 ethers by phosphorylation and phosphinylation

The primary hydroxy groups of head‐tail and head‐head bis(sugar)‐based crown ethers ( 1 and 3 , respectively) were acylated by (EtO)₂P(O)Cl and Ph₂P(O)Cl in a selective manner. Cation binding ability of the bis‐phosphorylated and phosphinylated macrocycles ( 2 and 4 ) was evaluated by the picrate extraction method. Introduction of the P‐moieties led to increase of the extraction ability without significant selectivity. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:267–270, 2000     

Influence of surface chemistry on the SAXS response of polymer-based activated carbons

Small-angle X-ray scattering (SAXS) measurements using contrast variation are reported for activated carbons prepared from poly(ethyleneterephthalate). The carbon surfaces are functionalized to different degrees by cold and hot nitric acid treatment. The latter treatment reduces the surface area by 75%, but the pore size distribution in the micropore range is hardly affected. Seven liquids, n-hexane, i-octane, i-propanol, cyclohexane, toluene, alpha-pinene, and nitrobenzene, in addition to water vapor, were used as contrast modifiers. Although the values of the specific surface area S(X) deduced from these measurements are relatively insensitive to the solvent, the detailed SAXS spectra reveal interactions occurring on different spatial scales that depend on the surface chemistry of the carbon and on the physicochemical properties of the solvent. In the most heavily oxidized sample, the amphiphilic molecule i-propanol stabilizes the surface structure, whereas nonpolar molecules make the rough surface smoother. In the untreated and the lightly functionalized carbons, water vapor at 50% relative humidity condenses only partially in the micropores at room temperature, whereas in the heavily treated sample condensation in the micropores is practically complete.     

Magnetic field dependence of residual dipolar couplings measured in dilute liquid crystalline media

The effect of the magnetic field strength on the magnitude of residual dipolar couplings introduced by dilute liquid crystal media was investigated. One-bond heteronuclear residual dipolar couplings and residual deuterium quadrupolar splitting of the water were monitored at various static magnetic fields. It is suggested that the value of residual anisotropic NMR parameters resulting from exchange between ordered and non-ordered molecules decreases with increasing magnetic fields.     

Kinetics and mechanism of the hydrolytic disproportionation of iodine

Kinetics of the hydrolytic disproportionation of I₂ was studied by UV–VIS spectrophotometry at 298 K and at the ionic strength 0.2 M (NaClO₄) in buffered solutions in the pH range 8.91–10.50 at different initial iodide concentrations. The characterization of this reaction is fundamental for modeling oscillatory and front reactions in the presence of iodine as reactant or intermediate as well as for drinking water treatment. A matrix rank analysis confirmed three absorbing species in the beginning of the reaction, whereas later assumption of two species is enough to describe the experimental data in the visible part of the spectrum. A reaction mechanism was proposed for disproportionation by using fitting/simulation with a multipurpose program package ZiTa, by simultaneous evaluation of 17,906 points in 79 experimental curves. A parameter set was suggested, which was obtained by absolute, relative, and orthogonal fittings of the experimental data. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 596–602, 2004     

New 7‐phosphanorbornenes derived from 2‐methyl‐1‐phenyl‐ and 1‐cyclohexyl‐3‐ methyl‐2,5‐dihydro‐1H‐phosphole 1‐oxides

Novel 7‐phosphanorbornene derivatives, such as 4, 5, 10 , and 11 were synthesized utilizing 1‐phenyl‐2‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) and 1‐cyclohexyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 7 ) as the starting materials. Products 4 and 10 were prepared by trapping the corresponding phosphole oxide intermediates ( 3 and 9 , respectively) by N‐phenylmaleimide, while 5 and 11 were obtained by the dimerization of 3 and 9 , respectively. The trapping reaction was studied in details; on one hand, bromo‐2,3‐dihydro‐1H‐phosphole oxides ( 6‐1 and 6‐2 ) were pointed out as the intermediates, on the other hand, the trapping reaction was optimized. Bri‐ dged P‐heterocycles 4, 5, 10 , and 11 were tested in the fragmentation‐related phosphorylation of methanol. Hydrogenation of phosphanorbornenes 4 and 5 led to the corresponding phosphanorbornanes ( 12 and 14 , respectively) and to a reductive type of retro cycloaddition. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:320–326, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20097     

Co2?+? interaction with Azospirillum brasilense Sp7 cells: a 57Co emission M?ssbauer spectroscopic study

The Thylacine Hole–001 meteorite was recovered from the Nullarbor Desert (Australia) in 1977 and is an Ordinary Chondrite, Group H4/5br, which has undergone moderate to severe (B/C) weathering. We have characterised the Fe-bearing phases in Thylacine Hole–001 by ⁵⁷Fe M?ssbauer Spectroscopy at 300?K, 100?K, 50?K and 4?K. The spectrum at 300?K is dominated by the paramagnetic doublets of Olivine, Pyroxene and a Ferric component which is most likely nanoparticulate Goethite. Magnetically split sextets due to Maghemite or Magnetite are also present, consistent with the relatively advanced terrrestrial age of 28,500 yrs The nanoparticulate Goethite component shows a blocked, magnetically split sextet at low temperatures. We also observe the effects of magnetic ordering of the Olivine and Pyroxene below 50?K.     

The synthesis of six‐membered P‐heterocycles with sterically demanding substituent on the phosphorus atom

The ring enlargement of 1‐(2,4,6‐trialkylphenyl)2,5‐dihydro‐1H‐phosphole oxides ( 1 ) via 6,6‐dichloro‐3‐Phosphabicyclo[3.1.0]hexanes ( 2 ) afforded the double‐bond isomers of 1,2‐dihydrophosphinine oxides ( 3 ). Catalytic hydrogenation of the isomeric 1‐(di‐tert‐butyltolyl)‐1,2‐dihydrophosphinine oxides ( 3a ) gave the diastereomers of phosphinane oxide ( 4 ), while that of the 1‐(tri‐isopropylphenyl) isomers ( 5 ) led predominantly to phospholane oxides ( 6 ) formed by ring contraction. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:528–533, 2001     

Convergence chromatographic determination of camphor in the essential oil of Tanacetum parthenium L.

Feverfew (Tanacetum parthenium L., Asteraceae) is a perennial medicinal plant which has been used to alleviate the symptoms of migraine, headache and rheumatoid arthritis and possesses numerous pharmacological activities. An ultra‐high‐performance supercritical fluid chromatographic method (UHPSFC) was developed and validated in accordance with the International Conference on Harmonization guidelines in order to determine the camphor content of the volatile oil, which was accurate, precise, robust and selective. The method was validated for specificity, accuracy (100.2%), repeatability and intermediate precision, linearity (r² > 0.999), limit of detection (2.055 μg/mL), limit of quantification (6.228 μg/mL) and robustness. The common range of accuracy and linearity was between 0.125 and 1.000 mg/mL. Steam distillation was carried out in order to study the essential oil yield of three different T. parthenium L. samples originating from Hungarian medicinal herb collections. The camphor content of the essential oils from the aerial parts of feverfew samples from different origin was compared. Although the composition of the essential oil is well reported, a validated quantitative UHPSFC method for the determination of the constituents is presented herein for the first time.