Z,E-isomerism of fluorinated mono- and diacylhydrazines

Conclusions It was established by the¹H and¹⁹F NMR method that the insertion of fluorine atoms in the acyl radical of mono- and diacylmethylhydrazines has a substantial effect on the population of the rotamers, without noticeably changing the activation energy of the E-Z isomerization.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1897–1901, August, 1979.     

Reaction of some 2-(N-trimethylsilyl) amino-1,3,2-oxazaphospholanes with benzaldehyde

Conclusions The reaction of 2-(N-trimethylsilyl)amido-1,3,2-oxazaphospholanes with benzaldehyde proceeds on the phosphorus atom with migration of the trimethylsilyl group onto the carbonyl oxygen and the formation of cyclic imidophosphonates. The latter, depending on the character of the substituent at the imide nitrogen atom and the conditions of carrying out the reaction, can be converted into phosphonates or decomposed into the original reactants.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1093–1097, May, 1979.     

Chemoselective reactions of trimethylsilylpropynal with aminopyrimidines and amino acid esters

Highly efficient chemoselective 1,2-addition of 2-aminopyrimidines and D,L-amino acid esters to substituted propynals was performed. Acid-catalyzed addition of 2-aminopyrimidine and 2-amino-4-methylpyrimidine to trimethylsilyl- and phenylpropynals gave previously unknown acetylenic aminals. Reactions of α-amino acid methyl esters (alanine and lysine) with trimethylsilylpropynal led to the formation of new aza enynes in high yield. Regardless of the reactant ratio, trimethylsilylpropynal reacted with lysine at both amino groups with formation of bis-aza enyne.     

Sensitive and selective detection of zinc ions in neuronal vesicles using PYDPY1, a simple turn-on dipyrrin

A new class of in vitro Zn(II) chemosensor based on dipyrrin has been developed. 5-(Pyren-1-yl)-4,6-dipyrrin (PYDPY1) was synthesized and exhibited high selectivity and sensitivity to Zn(II) (K(d) of 20 μM) compared to other metal ions. PYDPY1 was applied to the visualization of Zn(II) concentration in hippocampal tissue.     

Free-radical chain oxidation of 1,4-dioxane and styrene in the presence of fullerene C60

The antiradical activity of fullerene C₆₀ was studied for the oxidation of 1,4-dioxane and styrene initiated by azobisisobutyronitrile and benzoyl peroxide as model reactions. The effective rate constants of the reaction of peroxyl radicals with fullerene C₆₀ (k ₇) and the stoichiometric inhibition factor (f _eff) were determined in air ( $P_{O_2 }$ = 0.21 atm) and oxygen ( $P_{O_2 }$ = 1.0 atm). The rate of the liquid-phase oxidation of 1,4-dioxane does not depend on $P_{O_2 }$ , and the effective rate constant of inhibition is k ₇ = (2.4 ± 0.2) × 10⁴ L mol^?1 s^?1. Chain termination in the oxidation of styrene occurs when C₆₀ reacts with both the peroxyl radicals (k ₇ = (1.2 ± 0.1) × 10³ L mol^?1 s^?1) and alkyl (k ₈ = 1.07 × 10⁷ L mol^?1 s^?1) radicals.     

Specific Solvation of a 4-DASPI Dye in a Water–Ethylene Glycol Binary Solvent

Optics and Spectroscopy - The solvatochromic shifts of the maxima of the absorption spectra of a 4-DASPI dye (4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide) in a water–ethylene glycol...     

Peculiarities of antiferromagnetic ordering in orthorhombic LiMnO<Subscript>2</Subscript>

Data on the antiferromagnetic ordering in orthorhombic lithium manganite LiMnO₂ are obtained from magnetic-susceptibility, calorimetry, and nuclear magnetic resonance studies. The minimal hysteresis and the absence of jumps in the temperature dependences of the sublattice magnetization M(T) and the magnetic susceptibility near T _N indicate that the ordering occurs through a continuous second-order phase transition. Within the critical temperature range, the M(T?T _N) variation is satisfactorily described by a power-law dependence with a critical exponent β = 0.25(4), which is substantially smaller than that predicted for 3D magnetic systems with isotropic Heisenberg exchange. The band structure of orthorhombic LiMnO₂ is calculated using the LMTO-ASA method. Taking into account the spin states of manganese ions, an adequate pattern is obtained for the density-of-states distribution with an energy gap near the Fermi level (～0.7 eV), which is in agreement with the measured electrical parameters of lithium manganite. The calculations demonstrate that the exchange interactions between Mn³⁺ ions leading to antiferromagnetic ordering are significantly anisotropic. It is found that small paramagnetic regions persist in the manganite below the Néel temperature, and it is concluded that the reason for this is partial structural disordering of LiMnO₂. As a result, a certain fraction of the manganese positions is occupied by lithium ions (Li_Mn) and vise versa (Mn_Li). These defects are not involved in the formation of the ordered magnetic structure and compose a paramagnetic fraction.