Synthesis of 3-methyl-7-phenylimidazo-[1,2-b]-1,2,4-triazine

The bromocyclization of 3-allylamino-5-phenyl-1,2,4-triazine gives 3-bromomethyl-7-phenyl-2,3-dibromo-1H-imidazo[1,2-b]-1,2,4-triazinium bromide, which is transformed into 3-methyl-7-phenylimidazo-[1,2-b]-1,2,4-triazine.Yekaterinburg Fire-Fighting Technical Institute, Ministry of Internal Affairs, Russian Federation, 620002 Yekaterinburg. Chelyabinsk State University, 454136 Chelyabinsk. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 110–111, January, 1998.     

Temperature Dependence of the Ratios of C—H (C—D) Bond Breaking Rates in Reactions of Cycloalkanes C5H10, C6H12, C6D12 with Adamantyl Carbocations in Sulfuric Acid

We have determined the differences in the parameters log A and E of the Arrhenius equations for the kinetic isotope effect (KIE) (c-C₆H₁₂/c-C₆D₁₂) and the 5/6 effect (c-C₅H₁₀/c-C₆H₁₂) in reactions of the C—H bonds of cycloalkanes with adamantyl (Ad⁺) carbocations (1-adamantanol in 92.8% H₂SO₄, 40-97 °C). We have established the compensation relations between log A and E for the kinetic isotope effect and the 5/6 effect for anthracene (AH⁺), hydroxymethyl (CH₂OH⁺), Ad⁺ carbocations and the hypothetical "infinitely strong reagent," supporting a hydride transfer mechanism in such reactions.     

Substituent Effects on Hydrogen Bonding in Watson–Crick Base Pairs. A Theoretical Study

We have theoretically analyzed Watson–Crick AT and GC base pairs in which purine C8 and/or pyrimidine C6 positions carry a substituent X = H, F, Cl or Br, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P. The purpose is to study the effects on structure and hydrogen bond strength if X = H is substituted by a halogen atom. Furthermore, we wish to explore the relative importance of electrostatic attraction versus orbital interaction in the above multiply hydrogen-bonded systems, using a quantitative bond energy decomposition scheme. We find that replacing X = H by a halogen atom has relatively small yet characteristic effects on hydrogen bond lengths, strengths and bonding mechanism. In general, it reduces the hydrogen-bond-accepting- and increases the hydrogen-bond-donating capabilities of a DNA base. The orbital interaction component in these hydrogen bonds is found for all substituents (X = H, F, Cl, and Br) to contribute about 41% of the attractive interactions and is thus of the same order of magnitude as the electrostatic component, which provides the remaining 59% of the attraction.     

Kinetics and Mechanism of the Oxidation of Alkanes and Alkenes with Peroxynitrous Acid in Aqueous Solution-Gas Phase Systems

The reactions of alkane and alkene oxidation with peroxynitrous acid (HOONO) in aqueous solution-gas phase systems were studied using a modified kinetic distribution method. The rate constants of oxidation of hydrocarbons (RH) were found to be unusual bell-shaped functions of the volume ratio between liquid and gas phases in a reactor. This result, as well as the previously found proportionality of the rate constants of the gas-phase RH + HOONO and RH + OH^· reactions for alkanes, alkenes, and alkylbenzenes, was quantitatively interpreted assuming the rapid equilibrium distribution of HOONO and RH between a gas and a solution, the formation of OH^· radicals in the two phases, and the interaction of these radicals with RH. The rate constant of peroxynitrous acid decomposition in the gas phase and the distribution coefficient of this acid between the gas phase and solution α = (0.4–2) × 10⁻⁶ were estimated. The capacity of HOONO for partition between different phases and for generation of OH^· radicals in either of these phases can be of paramount importance for understanding the mechanism of lipid membrane oxidation initiated by peroxynitrous acid.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 370–379.Original Russian Text Copyright © 2005 by Lobachev, Rudakov.     

Mechanism of alkyl iodide reduction to alkanes in aqueous solutions of Na2PtCl4?NaI?HClO4

Platinum(II) catalyzes the reduction of alkyl iodides to alkanes according to a mechanism involving oxidative addition of RI to Pt(II), reduction of the product complex RPt(IV) to RPt(II) by iodide ions and protolysis of the latter particle.

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(II) , RI Pt^II, - RPt^IV RPt^II .

     

2-Halo-2,4-dinitrothiolene-1,1-dioxides in Reaction with Pyridine

Russian Journal of Organic Chemistry -     

Correlations in 11B NMR spectra of dihalo derivatives of bis(1,2-dicarbollyl)cobalt(III)

In the ¹¹B NMR spectra of dihalo derivatives of bis(dicarbollyl)cobalt(III), we have identified a correlation between the ¹¹B NMR chemical shifts of substituted boron atoms and boron atoms found in other positions on the carborane skeleton. We have observed an increased shielding effect for fluorine atoms (compared with other halogens), manifested in an upfield shift of the ¹¹B NMR signals for antipodal and trans boron atoms. For the fluorine-containing compound Bu₄N⁺ [8,8′-F₂-3,3′-Co(1,2-C₂B₉H₁₀)₂]⁻, we propose the following sequence of electron density transfer: B(8) → {B(6) and B(10)} → B(4, 7). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 547–549 (cont.), July–August, 2006.     

Temperature dependence of the relative rate constants of the reactions of alkanes with oh radicals in aqueous solution

A study was carried out on the rate constant ratio (k _RH/k _EtH) in reactions of alkanes C₃H₈, n-C₄H₁₀, n-C₅H₁₂, n-C₆H₁₄, i-C₄H₁₀, c-C₅H₁₀, and c-C₆H₁₂ with OH radicals in water at 5-55°C and the relative activation parameters A _RH/A _EtH and E _EtH – E _RH. The values of E _EtH – E _RH in water and the gas phase have opposite signs. The values of k _RH/k _EtH decrease with increasing temperature in the gas phase but increase in water. The behavior of these reactions in water may be attributed to a solvent cage effect.     

Comparative experimental analysis of composite pulses in 14N NQR

Experimental results of comparing composite pulses in nitrogen-14 NQR, that are analogous to common 90 degrees RF pulses in powder, are presented. All tested pulses have been taken from publications in journals. Comparative diagrams of the measurement results for induction signals and echo signals are presented. The results of the measurements demonstrate that the best outcomes are achieved when the composite pulse (45)0(95)180(164)0 is used.     

Spin-echoes in nitrogen-14 quadrupolar spin-system with axially symmetric electric field gradient tensor

The behaviour of the magnetisation in the spin-1 system with the axial symmetry of the electric field gradient (EFG) tensor was analysed theoretically. The behaviour of the NQR signals in hexamethylenetetramine (C6H12N4) was also studied experimentally using the pulse NQR technique and sensitive equipment. It was shown that the axial symmetry of the EFG in a sample could not be the reason why spin-echo signals were not observed in conventional pulse experiments for the same type of sample. A very short spin-spin relaxation time T2 seems to be the reason of that. The signal-to-noise ratio was sufficient for measuring T2 in C6H12N4, which had not been reported earlier. Experimental results of applying certain pulse sequences to the 14N NQR in a sample are also presented.