The effect of functional substitution on thermal stability of pyridinylporphyrins under argon atmosphere

The data on thermal stability under argon atmosphere of a series of porphyrin ligands containing meso- and β-positioned electron-donor (Me, Et, or Ph) groups as well as electron-acceptor pyridinyl substituents differing in the heteroatom location are presented. Thermogravimetric analysis and electron absorption spectroscopy studies have shown that pyridinylporphyrins are thermally stable at heating to 360–500°С depending on the functional substitution in the molecule.     

Dibromotyrosine derivatives from the ethanol extract of the marine sponge Aplysina sp.: structures,transformations, and origin

Twenty nine 3,5-dibromotyrosine derivatives were isolated from the ethanol extract of the marine sponge Aplysina sp. (South China Sea) including the earlier unknown compounds, in particular, p-hydroxycyclohexadienone and p-hydroxycyclohexenone ketals. The isolated enones, dienones, and ketals can be transformation products of aeroplysinin-1 in the course of its reactions with water and alcohols.     

Direct amination of naphthopurpurin and mompain,sea urchin pigments,and their O-methyl ethers by the reaction with ammonia

Russian Chemical Bulletin - The regiochemistry of direct amination of 2-hydroxynaphthazarin (naphthopurpurin) and 2,7-dihydroxynaphthazarin (mompain), sea urchin pigments, and their O-methyl ethers...     

Sorption of Silver and Chemiluminescent Activity of Clinoptilolite

Sorption conditions of ions and colloidal particles of silver by a zeolite (clinoptilolite) and clays, and specific features of distribution of absorbed silver in clinoptilolite grains were studied. Temperature dependences of the intensity of heterogeneous chemiluminescence from samples of natural clinoptilolite and its modified forms were obtained. The activation energies of the luminescence-active chemisorption of oxygen on electron-donor centers of the zeolite surface and relative amount of centers were determined.     

Gas-Dynamic Processes in Two-Phase Flows in MHD Generators

A plane problem of a two-phase monodisperse flow of combustion products of plasma-forming composite solid propellants in the duct of a Faraday's MHD generator with continuous electrodes, including an accelerating nozzle, MHD channel, and diffuser, is considered. An algorithm based on the pseudo-transient method is developed to solve the system of equations describing the two-phase flow. Gas-dynamic processes in the channels of the Pamir-1 setup are numerically studied. It is shown that shock-free deceleration of a supersonic flow to velocities close to the equilibrium velocity of sound in a two-phase mixture and significantly lower than the velocity of sound in the gas is possible in two-phase flows.     

The chemistry of naphthazarin derivatives

The 7,7′-dideoxy analog of islandoquinone, binaphthazarin of a new structural type, bearing a 2-oxo-2,3-dihydro-1,4-naphthoquinone moiety was synthesized. The carbonyl group at the C(2) atom of this binaphthazarin easily adds water to give the correspondinggem-diol. Comparison of the spectral characteristics of the prepared diol and islandoquinone made it possible to elucidate more precisely the structure of the latter.