Chromogenic crown ether reagents for spectrophotometric determinations of sodium and potassium

Crown ethers carrying a phenolic group, 2-hydroxyphenoxymethyl-15-crown-5 and -18-crown-6, were synthesized. Introduction of nitro groups in the 3- and 5-positions of the aromatic nucleus or introduction of a 4-nitrophenylazo group in the 5-position gives a series of chromogenic reagents suitable for the extraction spectrophotometry of sodium and potassium. Sodium in human blood serum was successfully determined by using the (2-hydroxy-3,5-dinitrophenyl)oxymethyl-15-crown-5 reagent. The molar absorptivity of the sodium complex is 14 000 l mol^-1 cm^-1 at 423 nm.     

Measurement of high frequency ultrasound in liquids using high-resolution Bragg reflection technique

A new light scattering technique has been established for simultaneous measurement of ultrasonic velocity and absorption in liquids over a frequency range from 100 to 1000 MHz. The technique is applied to studies of vibrational relaxation in the uhf range, and the velocity-dispersion and absorption curves in several organic liquids are presented.     

XUV radiation transfer through high-Z metal foil in a laser-produced plasma

Aluminum and gold foils have been irradiated with 1.05-μm, 100-psec laser pulses at an intensity of 3 × 10¹⁴ W/cm². A spatially resolved spectrum of XUV radiation from a rear-side plasma has been observed in the wavelength range from 10 to 100 Å. The spectral intensity for the Al foil decays exponentially with foil thickness and goes to zero at 3 μm. The intensity for the Au foil also decays exponentially up to 1 μm but remains almost constant from 1 to 6 μm. This result for the Au foil indicates that radiation heat conduction plays an important role in energy transport through high-Z plasmas.     

Infrared-microwave double resonance in CH3OH using a Zeeman-tuned 3.5-μm HeXe laser

Infrared microwave double resonance signals have been observed for CH₃OH using the 3.5-μm HeXe laser line. When microwave transitions in the ground vibrational state are pumped, the double resonance signals are obtained on two infrared transitions v = 1 ← 0 of ν^CH(a′); v = 1, J, K, μ = 4, 2, 1 ← v = 0, J, K, μ = 3, 2, 1, and 4, 3, 1 ← 3, 3, 1. Three weak double resonance signals are due to the collision-induced transitions. Their relative intensities have been explained successfully by using the rate constants of collision-induced transitions which are proportional to the dipole matrix elements between the states involved in the transitions.     

Odd-even effect of the methylene chain number in the template polymerization of alpha,beta-diacetylenecarboxylates incorporated in layered double hydroxide clay

The present investigation reports on the significant differences observed in the efficiency of the polymerization depending on the odd- or even-numbered methylene chains of diacetylenecarboxylates, CH3(CH2)(m-1)C[triple bond]C-C[triple bond]C(CH2)(n-1)CO2- (mono-[m,n]), incorporated in layered double hydroxide (LDH) clay. Upon gamma-ray irradiation of the diacetylenecarboxylates, or mono-[m,n], in LDH clay, polymer hybrids or poly-[m,n]/LDH, which exhibited coloring from light orange to violet, were obtained. The color of the poly-[m,n]/LDH hybrids was strongly dependent on the extent of the polymerization degrees. Moreover, the polymerization degrees were controlled by the number of methylene spacers n between the carboxyl and diacetylene groups. An odd-numbered n for the methylene chain of mono-[m,n] was found to be the determining factor in the efficient polymerization of these self-assembling aggregates within the interlayers of LDH clay.     

Characterizations of isometric isomorphisms between uniform algebras via nonlinear range-preserving properties

Let be a surjective mapping from a uniform algebra on a compact Hausdorff space onto a uniform algebra on a compact Hausdorff space . Suppose that holds for every . Then we have that is an almost isometric isomorphism, which is a generalization of results of Molnár (2002) and Rao and Roy (2005).

     

Synthesis of bis(azafulvene)s by dehydration of hydroxymethylpyrrole derivatives

Bis(azafulvene) was isolated in 55% yield by the reaction of 4 equivalents of phenyllithium with 5,5'-diformyl-3,3',4,4'-tetraethyl-2,2'-bipyrrole followed by quenching with acetic anhydride. Unstable bis(azafulvene)s were obtained in much higher yields by dehydrating 5,5'-bis(hydroxymethyl) derivatives of 2,2'-bipyrrole and gem-dimethyl-2,2'-dipyrrylmethane with (Boc)2O-DMAP at room temperature. X-Ray crystallography of two bis(azafulvene)s is reported.     

Decomposition of anthranil. Single pulse shock-tube experiments, potential energy surfaces and multiwell transition-state calculations. The role of intersystem crossing

The thermal decomposition of anthranil diluted in argon was studied behind reflected shock waves in a 2 in. i.d. pressurized driver single-pulse shock tube over the temperature range 825-1000 K and overall densities of approximately 3 x 10(-5) mol/cm(3). Two major products: aniline and cyclopentadiene carbonitrile (accompanied by carbon monoxide) and four minor products resulting from the decomposition were found in the postshock samples. They were, in order of decreasing abundance, pyridine, CH(2)=CHCN, HCN and CHC-CN, and comprised only a few percents of the overall product distribution. Quantum chemical calculations were carried out to determine the sequence of the unimolecular reactions that lead to the formation of cyclopentadiene carbonitrile and of phenylnitrene/phenylimine that are the precursors of aniline. They form aniline by reactions with traces of water impurities. To produce cyclopentadiene carbonitrile, two main processes must take place: CO elimination and ring contraction from a six- to a five-membered ring. It was shown that this can occur via two parallel pathways where CO elimination takes place prior to or following ring contraction. Singlet potential energy surfaces for all the elementary reactions that lead to the formation of cyclopentadiene carbonitrile and phenylnitrene/phenylimine were obtained. Their rate constants were calculated on the basis of the results of the quantum chemical calculations using transition-state theory. A kinetic scheme containing these reactions was constructed and multiwell calculations were performed to evaluate the mole percent of the products as a function of temperature. A very serious disagreement between the experimental results and the results of calculations showed that the singlet PESs could not account for the observed experimental rates. No other singlet PESs that lead to the formation of these products could be found. In view of this observation, attempts to find pathways that lead to the formation of cyclopentadiene carbonitrile and phenylnitrene/phenylimine on triplet surfaces were made. Such surfaces were found, and singlet <--> triplet intersystem crossing probabilities and crossing rate constants were calculated as well as the rate constants of all the elementary steps on the triplet surfaces. A reaction scheme was constructed and multiwell calculations were performed, including also the pathways on the singlet surfaces, to evaluate the mole percent of the products as a function of temperature. The agreement between the experimental results and these calculations was quite satisfactory.     

Superconductivity of doped Ar@C60

The synthesis of a mg amount of pure argon containing fullerene allowed the synthesis of the first endohedral superconductors with critical temperatures lower than expected, an indication of the strong influence of the argon atom on the C60 cage.