Divergent 2-Chloroquinazolin-4(3H)-one Rearrangement: Twisted-Cyclic Guanidine Formation or Ring-Fused N-Acylguanidines via a Domino Process

A highly efficient 2-chloroquinazolin-4(3H)-one rearrangement was developed that predictably generates either twisted-cyclic or ring-fused guanidines in a single operation, depending on the presence of a primary versus secondary amine in the accompanying diamine reagent. Exclusive formation of twisted-cyclic guanidines results from pairing 2-chloroquinazolinones with secondary diamines. Use of primary amine-containing diamines permits a domino quinazolinone rearrangement/intramolecular cyclization, gated through (E)-twisted-cyclic guanidines, to afford ring-fused N-acylguanidines. This scalable, structurally tolerant transformation generated 55 guanidines and delivered twisted-cyclic guanidines with robust plasma stability and an abbreviated total synthesis of an antitumor ring-fused guanidine (4 steps, 55 % yield).     

Specific features of the thermal physical properties of relaxor ceramics based on lead zirconate titanate

The heat capacity and thermal expansion of ferroelectric relaxors based on lead zirconate titanate are studied near the diffuse phase transition. It is shown that no spontaneous phase transitions from the paraelectric phase to the ferroelectric phase and from the relaxor state to the normal ferroelectric state occur in an ensemble of nanometer-sized polar regions. It is noted that the transitions can be caused only by external electric fields or storage for a fairly long time.     

Multibubble sonolysis and sonoluminescence in molten elementary sulfur and sulfur—styrene mixture

The effect of saturation with argon, as well as styrene and iodine additives on the temperature dependence of multibubble sonoluminescence intensity in molten sulfur at 120–230 °C was studied. The shape of the temperature dependence with a maximum at 170–200 °C is determined by the viscosity variations related to the changes in the molecular structure of molten elemental sulfur. At high temperatures, cyclooctasulfane (S₈) molecules break to radical products, which then undergo polymerization that can be slowed down by the additives. Sulfurization of styrene during sonolysis of a sulfur—styrene mixture resulting in products of the thiophene series was detected. Unlike thermal sulfurization that affords 2,5-diphenylthiophene as a major product, sonochemical sulfurization results mainly in 2,4-diphenylthiophene. The mechanism of 2,4-diphenylthiophene formation initiated by the reaction of styrene molecules with S⁺ ions produced upon fragmentation of S₈ within cavitation bubbles is proposed. The glow of electronically excited S⁺* ions is responsible for the band with a maximum at 560 nm in the sonoluminescence spectrum of molten sulfur, which is suppressed by the styrene additive.     

On the Stability of Pt-Based Catalysts in HBr/Br2 Solution

Stability studies on supported metal nanoparticles are essential for gaining insight into the design and optimization of high-performance materials. In this work, the dissolutions of Pt-based catalysts in HBr/Br₂ mixture of various concentration regimes were studied and correlated with material structural properties. The dissolution of metal nanoparticles was enhanced by adding Br₂ to the HBr solution. Comparing with commercial Pt/C catalyst, the well-alloyed PtIr/C catalyst was observed to exhibit high resistance towards dissolution. In addition, regulating the accessibility of the metal sites to dissolution-inducing species contributed to the marked stability of the nanoparticles in HBr/Br₂ solutions, as shown for the surface-modified PtIr/C catalysts with organic diamine molecules.     

Ammonium sulfatophosphate producing from the phosphorites of Central Kyzylkum

The necessity of using sulfur-containig fertilizers in agricultural production is evidenced. By neutralizaation with gaseous amonia of a mixture of extractive phosphoric and sulfuric acids the ammonium sulfatophosphates are produced, containing nitrogen, phosphorus and sulfur in various ratio. The regimes for producing them are described and material flows in the industrial manufacturing are given.     

On the application of ICP-MS techniques for measuring uranium and plutonium: a Nordic inter-laboratory comparison exercise

Inductively coupled plasma mass spectrometry (ICP-MS) techniques are widely used for determination of long-lived radionuclides and their isotopic ratios in the nuclear fields. Uranium (U) and Plutonium (Pu) isotopes have been determined by many researchers with ICP-MS due to its relatively high sensitivity and short measurement time. In this work, an inter-laboratory comparison exercise among the Nordic countries was performed, focusing on the measurement of U and Pu isotopes in certified reference materials by ICP-MS. The performance and characters of different ICP-MS instruments are evaluated and discussed in this paper.     

Crystal structure and nontrivial magnetic properties of CuII binuclear complex based on 4-methyl-2,6-bis{[2-(4,6-dimethyl-pyrimidin-2-yl)hydrazono]methyl}phenol

1. Download high-res image (167KB)
2. Download full-size image