Addition reactions of a phosphorus triamide to nitrosoarenes and acylpyridines

Abstract

Tricoordinate phosphorus compounds react with a wide variety of double bonds through addition reactions. The dipolar and cyclic products formed are important intermediates in organophosphorus chemistry. We investigated the reactivity between phosphorus triamide 1 and nitrosoarenes and 2-acylpyridines. For sterically congested substrates, the formation of σ⁵ Aroyan, C. E.; Dermenci, A.; Miller, S. J. The Rauhut–Currier Reaction: A History and Its Synthetic Application. Tetrahedron 2009, 65, 4069–4084. DOI: 10.1016/j.tet.2009.02.066.[Crossref], [Web of Science ®] , [Google Scholar],λ⁵-phosphorus products is observed. DFT calculations indicate this product is formed through a concerted [4?+?1] mechanism. For less sterically congested substrates, products are observed arising from cleavage of the N?=?O or C?=?O bond with formation of a terminal P?=?O bond and aryl nitrene or carbene migration into a P–N bond of the phosphorus triamide core. DFT calculations are consistent with an initial [2?+?1] addition to phosphorus followed by formal carbene/nitrene migration in these cases.     

A Titration Microcalorimetric Study of the Effects of Halide Counterions on Vesicle-Forming Aggregation in Aqueous Solution of Branched-Chain Alkylpyridinium Surfactants

Titration microcalorimetry is used to study the influences of iodide, bromide, and chloride counterions on the aggregation of vesicle-forming 1-methyl-4-(2-pentylheptyl)pyridinium halide surfactants. Formation of vesicles by these surfactants was characterised using transmission electron microscopy. When the counterion is changed at 303 K through the series iodide, bromide, to chloride, the critical vesicular concentration (cvc) increases and the enthalpy of vesicle formation changes from exo- to endothermic. With increase in temperature to 333 K, vesicle formation becomes strongly exothermic. Increasing the temperature leads to a decrease in enthalpy and entropy of vesicle formation for all three surfactants. However the standard Gibbs energy for vesicle formation is, perhaps surprisingly, largely unaffected by an increase in temperature, as a consequence of a compensating change in both standard entropy and standard enthalpy of vesicle formation. Interestingly, standard isobaric heat capacities of vesicle formation are negative, large in magnitude but not strikingly dependent on the counterion. We conclude that the driving force for vesicle formation can be understood in terms of overlap of the thermally labile hydrophobic hydration shells of the alkyl chains. Copyright 2000 Academic Press.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

Chaotic dynamics of a semiconductor laser with double cavity feedback: Applications to phase shift keying modulation

We report results on the numerical investigations of the dynamical behavior of a single mode semiconductor laser under the influence of double cavity optical feedback. We find that the system displays, under certain conditions, chaotic behaviors appropriate for chaos based communications. The synchronization of two unidirectional coupled (master-slave) systems is also studied. The influence of some parameters on the resynchronization and autocorrelation times is investigated. We find that the resynchronization time for the proposed scheme can be two orders of magnitude shorter when compared with that of the single-cavity feedback case. Very good conditions for message encoding by using the on/off phase shift keying encryption method are identified and examples of message encoding/decoding are presented.     

Intravascular and Intracellular Hepatic Relaxivities of Superparamagnetic Particles: An Isolated and Perfused Organ Pharmacokinetics Study

The relative contributions of intravascular and intracellular compartments to the proton transverse relaxation of the isolated and excised rat liver were determined during the phagocytosis of superparamagnetic particles. The evolution of the proton transverse magnetization of the organ perfused with increasing doses of starch-coated magnetic microspheres was followed up using a Carr–Purcell–Meiboom–Gill sequence with various echo times. From the multiexponential fit of the echo train, the amplitudes and the relaxation ratesR₂of the liver tissue were obtained. The results clearly indicate that shortly after contrast medium administration, an internalization takes place which can be followed by the rapid and biphasic evolution of the transverse relaxation rate of the water protons. A very fast decaying component looking like an initial loss of the magnetization is observed together with an increase of the relaxation rate of the remaining water tissue. This regime is strongly dependent on both the echo time and the iron concentration, a behavior characteristic of the agglomeration of magnetic particles. The examination of the liver tissues by electron microscopy shows that this clustering arises in cytoplasmic vacuoles.