Effect of monomer functional groups on the composition of some three component random phenolic copolymers

Some three-component random phenolic copolymers were prepared from three typical phenolic monomers; for example, p-chlorophenol, p-aminophenol, and p-cresol. Several samples of the copolymer were prepared by changing the feed composition and the composition of the copolymers was established by estimating ? NH₂ and ? OH groups by electrometric titration techniques in nonaqueous media. Halogen was estimated by Volhard's method. The average degree of polymerization (DP) of the copolymers was calculated from the features of the electrometric titration curves, and the effects of monomer functional groups on the composition of the copolymers were interpreted in terms of the electron-donating and electron-attracting nature of the substituents present in the monomers.     

Catalytic properties of metal-containing oxidized coal catalysts in some redox reactions

An increased activity in some redox reactions was observed for some metal ions bound by ion-exchange to oxidized coals. The similarity of the catalytic properties of oxidized coals modified by Fe(III), Cu(II), Mn(II) and other cations has been established for various redox reactions: decomposition of H₂O₂, oxidation of some organic and inorganic substances by hydrogen peroxide and oxygen. The catalytic activity of the modified coals depends on how the modifying additive is bonded to the surface and the amount of the dopant. New methods for the practical use of catalysts with regulated activity are noted. Translated from Teoreticheskiya i éksperimental’naya Khimiya, Vol. 33, No. 4, pp. 256–260, 1997.     

Modular design of icosahedral metal clusters

The concept of crystalline module, that is, an unambiguously isolated, repeated quasi-molecular element, is introduced. This concept is more general than the concept of crystal lattice. The generalized modular approach allows extension of the methods and principles of crystallography to quasi-crystals, clusters, amorphous solids, and periodic biological structures. Principles of construction of aperiodic, nonequilibrium regular modular structures are formulated. Limitations on the size of icosahedral clusters are due to the presence of spherical shells with non-Euclidean tetrahedral tiling in their structure. A parametric relationship between the structures of icosahedral fullerenes and metal clusters of the Chini series was found.     

Cage: software for a critical analysis of (2)H spin-lattice relaxation in liquid crystals

A software package of Mathematica, aimed at the analysis of (2)H NMR Zeeman (T(1Z)) and quadrupolar (T(1Q)) spin-lattice relaxation times in liquid crystals in terms of diffusional models, is presented. The models most commonly used to describe internal, overall, and collective motions in liquid-crystalline phases are considered, and dynamic parameters are obtained by means of either single point or global target approaches using simulation or fitting procedures. The use of the software as a tool for highlighting the problems encountered in this kind of analysis as well as for dealing with such problems following suitable strategies is illustrated by means of applications to experimental (2)H relaxation times of three different calamitic liquid crystals.     

Synthesis of 2-substituted isoxazoline and imidazoline,containing a vinylacetyl fragment

The reaction of4-dialkylamino-1-acetyl-1-buten-3-ynes with 1-hydroxy-2-aminoethane and 1,2-diaminoethane was used to synthesize 2-substituted oxazoline and imidazoline, containing a fully enolized vinylacetyl fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1409–1410, October 1992.     

Application of the slotted quartz tube in flow-injection flame atomic-absorption spectrometry

The slotted quartz has been applied to flow-injection flame atomic-absorption spectrometry (FI-FAAS) showing several important advantages. The tube life was improved by a factor of 5-6 compared to conventional continuous aspiration. Flow impact systems were found not to be necessary in the applications so that larger enhancement factors may be achieved without sacrifice in precision. For 1.0 mg/l. copper, 1.0 mg/l. lead, 0.1 mg/l. cadmium and 1.0 mg/l. gold sensitivity enhancement factors of 3.1, 5.5, 5.3 and 4.0 were obtained with precisions of 1.3%, 1.1%, 1.6% and 1.7% RSD (n = 11) respectively. Application of the slotted quartz tube FI-FAAS method to the determination of heavy metals in urine has shown improved tolerance to interfering matrices. Recoveries obtained by spiking undiluted urine samples with 0.1 mg/l. copper and lead, and 0.01 mg/l. cadmium were in the range 100-102%.     

Bromination of sydnones. III. Bromination of 3-(2-substituted-phenyl)sydnones and subsequent side chain modification

Bromination of the sydnone ring of several ortho-substituted N-arylsydnones is reported. Subsequent side-chain modification generally can be achieved without concomitant removal of the 4-bromo protective group.     

Méthylène-indolines,indolénines et indoléniniums—XIII: L'hydroxy-16 déhydro-1 vincadifformine,intérmédiaire dans le réarrangement biomimétique de la vincadifformine en vincamine

The title compound is a crucial intermediate in the biomimetic conversion of vincadifformine 1 into vincamine 7. Its configuration at C-16 is established by a combination of chemical and spectroscopic evidence. Iodine oxidation converts 14 into the bridged lactam 18, thus proving a β configuration for the hydroxy group at C-16. The same reaction applied to vindoline 19 gives 21 identical with one of the compounds obtained by microbiological transformation of 19. The ¹³C NMR spectra of derivatives 3 and 8 (obtained by oxidation of vincadifformine) show that oxidation proceeds with introduction of the substituent at C-16, with a β-configuration. The alcohol 3 however, posesses a different conformation due to strong hydrogen bonding with N-4.     

The use of naphthalene derivatives in inorganic analysis : The nitronaphthylamines as new reagents for mercuric mercury and ceric cerium

The use of 4-nitro-1-naphthylamme as a spot test for mercuric mercury and 1-nitro-2-naph-thylamine as a specific spot test for ceric cerium have been observed In each case, the reactions appear to be suitable for general qualitative inorganic analysis The ceric cerium test was specific whereas in the case of mercuric mercury. Ce⁺⁴ was the only on of 51 tested which interfered.