Nanostructuring in the process of the formation of mixed-anion compounds: Rare-earth borogermanates, germanophosphates, and borotungstates

Specific features of the textures (the preferred orientation of the nanometer building blocks) in the structures of mixed-anion compounds—rare-earth borogermanates, germanophosphates, and borotungstates that arise from the acid-base interaction in the Ln₂O₃-B₂O₃-GeO₂, Ln₂O₃-GeO₂-P₂O₅, and Ln₂O₃-B₂O₃-WO₃ systems (Ln = La-Gd)—have been studied. Based on characteristic texture traits, the mixed-anion compounds of early rare-earth elements can be divided into three groups: (i) Ln₂O₃: E_xO_y > 1, (ii) Ln₂O₃: E_xO_y = 1, and (iii) Ln₂O₃: E_xO_y < 1. Because of the dominant structural effect of the basic oxide Ln₂O₃ in the compounds of the first group, the structures of Nd₁₄O₈(BO₃)₆(GeO₄)₂ and Pr₁₁O₁₀(GeO₄)(PO₄)₃ are composed of infinite [LnO_n] bands and layers and discrete groups [EO_m] located in the interband and interlayer spaces. The dominant structural effect of the acid oxides [E_xO_y] in the compounds of the third group leads to the appearance of ring textures composed of [LnO_n], as well as to the appearance of chains and networks composed of [EO_m], in the structures of Ln(BGeO₅) and Ln(BO₂)(WO₄). Original Russian Text ￠ G.A. Bandurkin, N.N. Chudinova, G.V. Lysanova, K.K. Palkina, E.V. Murashcva, V.A. Krut’ko, G.M. Balagina, 2006, published in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 2, pp. 334–347.     

Electrochemical reduction of 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one

The properties of 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one which contains the trichloromethyl substituent at a quaternary carbon atom have been studied by cyclic voltammetry, rotating disk electrode voltammetry, and preparative electrolysis. Reductive dehalogenation involves initial two-electron reductive elimination of one of the geminal chlorine atoms followed by consecutive addition of proton, simultaneous elimination of the two residual halogen atoms to form carbene, and rearrangement of cyclohexadienone into the corresponding 4-methylcyclohepta-2,4,6-trien-1-one.     

Topochemistry regularities in evaluation technique of phosphate raw material reactivity

Experimental approaches for evaluation of reactivity of phosphate raw material and obtaining additional information on its phase composition were suggested in view of physicochemical patterns of the phosphate raw material decomposition in a weakly acidic environment.     

Isotropic cationic networks in the structures of rare earth compounds

The isotropic cationic networks (CNs) completing the anisotropic CNs ai isotropic CNs binary opposition are identical in the structures of various rare earth compounds.     

Physicochemical aspects of phosphorite powder decomposition by weak acid

Fundamental aspects of phosphorite powder decomposition by citric acid were studied.     

Complexation of calix[4]arenehydroxymethylphosphonic acids with amino acids. Binding constants determination of the complexes by HPLC method

Host–Guest complexation process of calixarenehydroxymethylphosphonic acids with 10 amino acids in solution H₂O/MeCN (99:1) had been studied. Binding constants of the inclusion complexes from the dependence between capacity factors of the Guest and the calixarene-Host concentration in the mobile phase had been calculated. It was shown the binding constants depend on the nature of the amino acid residue, conformation of the calixarene skeleton, quantity of phosphoryl groups at the upper rim. In accordance with molecular calculation the complexation is determined by the electrostatic interactions between the positively charged nitrogen atom of amino acid and the negatively charged oxygen atom of phosphonic group of calixarene molecule, hydrogen bonds, π–π, CH–π and solvatophobic, interactions.     

Trends in the cation distribution in the structures of the compounds forming in the Ln<Subscript>2</Subscript>O<Subscript>3</Subscript>-GeO<Subscript>2</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> systems

The cationic networks in the structures of the initial oxides and all binary and ternary compounds forming in the Ln₂O₃-GeO₂-P₂O₅ systems have been studied. In the phase diagrams of the Nd₂O₃-GeO₂-P₂O₅ and Er2O₃-GeO₂-P₂O₅ systems, the regions of the structural influence of individual compounds with topologically identical cationic networks—anisotropic (A), combined (C), and isotropic (I)—are united into common areas. The A: C: I area ratio is 1: 1: 1 in the neodymium system and 1.7: 1: 3.4 in the erbium system.     

Controlled free-radical copolymerization of maleic anhydride and divinyl ether in the presence of reversible addition-fragmentation chain-transfer agents

The free-radical alternating cyclocopolymerization of maleic anhydride and divinyl ether is studied at 60–80°C in the presence of benzyl dithiobenzoate and dibenzyl trithiocarbonate as reversible addition-fragmentation chain-transfer agents. It is shown that the structure of the repeating unit of the cyclocopolymer prepared in the presence of a reversible addition-fragmentation chain-transfer agent coincides with the structure of the repeating unit of the copolymer synthesized under the conditions of conventional free-radical cyclocopolymerization. When the cyclocopolymer is used as a reversible addition-fragmentation chaintransfer agent, a successive increase in the molecular mass of the copolymer with conversion and formation of the block copolymer in the polymerization of styrene are unambiguous evidence that the copolymerization proceeds according to the pseudoliving radical mechanism.