Structure of KTiOAsO<Subscript>4</Subscript> single crystals at 293 and 30 K

The unit cell parameters of KTiOPO₄ and KTiOAsO₄ single crystals are measured in the temperature range from room temperature to 20 K. It is found that the unit cell volume of the single crystals changes smoothly. With a decrease in temperature, the c parameter remains almost unchanged. In a certain temperature range, the linear temperature dependence of the a and b parameters is violated. An X-ray diffraction study of KTiOAsO₄ single crystals is performed at T = 293 and 30 K. With a decrease in temperature, the electron density in the channels of the structure undergoes a redistribution, suggesting that at room temperature the state of the potassium ions is characterized by the dynamic and static disordering. The nonuniformity of the distribution of the electron density at the junctions of TiO₆ octahedra and AsO₄ tetrahedra is significantly enhanced in relation to that at the corresponding junctions in the KTiOPO₄ structure. It has been experimentally established that the geometry of the tetrahedral anions makes a decisive contribution to the nonlinearity of KTiOAsO₄ single crystals.     

Aqueous solution ofN-methylmorpholineN-oxide as a stationary liquid phase in steam chromatography

The retention of more than 70 voltatile organic compounds of different classes was studied by steam chromatography using aqueous solutions ofN-methylmorpholineN-oxide as the stationary liquid phase (SLP). The effects of temperature and composition of the mobile phase on the retention factors (k) for polar and nonpolar sorbates were elucidated. An unusual order of elution of aliphatic alcohols was noted, namely,tert-butyl alcohol <sec-butyl alcohol < isopentyl alcohol <isobutyl alcohol<isopropyl alcohol <n-pentyl alcohol <n-butyl alcohol <n-propyl alcohol <ethanol <methanol. The retention of cyclohexanol was longer than those of benzyl alcohol andn-hexyl alcohol. Nitrogen-containing compounds were selectively separated on the water-organic SLP studied. For example, the retention of aniline was much longer than those of its derivatives,N,N-dimethylaniline andN,N-diethylaniline, having higher boiling points. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1077–1084, June, 2000.     

Synthesis, atomic structure, and properties of crystals in the RbTiOPO4-CsTiPO5 system

The subsolidus region of the phase diagram of the RbTiOPO₄-CsTiPO₅ system has been studied in the temperature range 700–1000°C, and the boundaries between the stability fields of the orthorhombic phase with the KTiOPO₄-type structure and the cubic phase with the pyrochlore-type structure have been determined. Single crystals of the RbTiOPO₄ and CsTiPO₅ based solid solutions were synthesized by crystallization from flux. The crystal structure and the physical properties of the first members of the series were studied.     

Structure and properties of niobium-doped potassium titanyl phosphate crystals

A series of potassium titanyl phosphate crystals, KTiOPO₄, with various concentrations of niobium dopant has been grown, and some of their physical properties and structural characteristics have been studied. The incorporation of a small amount of niobium results in considerable changes in the electrical conductivity of KTP: Nb crystals and the temperature of the ferroelectric phase transition. Thus, the presence of 3–4 at. % of niobium results in an increase of conductivity by more than an order of magnitude, whereas T _C decreases from 930 to 620°C. The X-ray diffraction study of the crystals has been performed at room temperature; the neutron diffraction analysis was made at temperatures of 20, 330, and 730°C. It was revealed that two crystallographically independent positions are statistically (by 90%) occupied by potassium cations, which results in the concentration of potassium atoms in the structure higher than it was expected from the condition of preservation of crystal electroneutrality. At high niobium concentrations, the monoclinic compound of the composition K₂TiNb₂P₂O₃ is formed.     

Growth, structure, and properties of ferroelectric—ferroelastic— superionic K3Nb3B2O12 and K3−x NaxNb3B2O12 crystals

The potassium niobate-borate K₃Nb₃B₂O₁₂ (KNB) crystals and their solid solutions with partial substitution of potassium by sodium (KNB: Na) are grown from flux and their physical properties are studied. The specific feature of the crystals grown is a complicated polymorphism and the unique combination of ferroelectric and ferroelastic properties with superionic conductivity with respect to potassium ions.     

7-Dialkylaminomethyl-2,4,5-trimetyl-and 2,4,5-trimethyl-7-phenylminomethyl-1,2,3,4-tetrahydropyrrolo[1,2-c]pyrimidines

The Mannich aminoalkylation of 2,4,5-trimethyl-1,2,3,4-tetrahydropyrrolo[1,2-c]pyrimidine and condensation of its 7-formyl derivative with aniline have been studied. 7-Morpholinomethyl- and 7-(N-methylpiperazinylmethyl)-substituted derivatives have been isolated. 7-Dimenthylaminomethyl- and 7-phenyliminomethyl-substituted derivatives of tetrahydropyrrolo[1,2-c]pyrimidines are easiliy cleaved in the process of chromatographic isolation.Russian Peoples' Friendship University, Moscow 117198Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1659–1663, December, 1999.     

Steam chromatography of aliphatic and aromatic amines on packed columns with aqueous potassium hydroxide as the stationary liquid phase

Aqueous alkali was proposed as the stationary liquid phase (SLP) for separation of amines by steam chromatography. Characteristic features of retention of amines of various structures were studied. The retention of primary and secondary amines on aqueous potassium hydroxide as the SLP differs fundamentally from that observed with common organic SLP. Primary amines are eluted in the following order,n-pentylamine <n-butyl-amine <n-propylamine <n-hexylamine <n-octylamine for secondary amines, the following sequence was established; diethylamine < dibutylamine < dimethylamine. Higher-boiling tertiary amines containing ethyl andn-butyl radicals are eluted ahead of diamines containing the same radicals. Translated fromIzvestiya Akademii Nau. Seriya Khimicheskaya, No. 8 pp. 1507–1509, August, 1999.     

New methods of synthesis of boron,germanium, and tin derivatives of pentavalent phosphorus thioacids

The reactions of S‐trimethylsilyl esters of S‐propyl‐4‐methoxyphenyltrithiophosphonic, bis(dialkylamido)dithiophosphoric, and S‐ethyl‐diethylamidotrithiophosphoric acids with trialkyl borates, triorganylbromogermanes, trimethyl(isobutylthio)germane, and trialkylchlorostannanes were studied. On the basis of these studies, new methods of synthesizing S‐boron, S‐germyl, and S‐stannyl derivatives of pentavalent phosphorus thioacids were developed. S‐Diethylaminomethyl O‐isopropyl‐4‐ethoxyphenyldithiophosphonate was obtained by the reaction of the diisopropylboron derivative of the corresponding dithiophosphonic acid with the aminal 6 . © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:27–35, 2002; DOI 10.1002/hc.1103