Tetrazoles. 24. Preparation of 1,4-dimethyl- and 2,4-dimethyl-5-aryl-tetrazolium salts

Alkylation of 1-methyl-5-aryltetrazoles with dimethyl sulfate leads to the formation of 1,4-dimethyl-5-aryltetrazolium ion salts. Alkylation of isomeric 2-methyl-5-aryltetrazoles also apparently takes place at the N(4) atom. 1-Methyl-5-aryltetrazoles display greater reactivity with respect to methylation than the isomeric 2-methyl-5-aryltetrazoles. 1,4-Dimethyl-5-aryltetrazolium methylsulfate salts isomerize upon heating to give the more stable 2,4-dimethyl-5-aryltetrazolium ion salts.For Communication No. 22, see Ref. [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 502–506, April, 1988.     

Application of compact and multioperator schemes to the numerical simulation of acoustic fields generated by instability waves in supersonic jets

Acoustic fields generated by instability waves in supersonic jets were numerically simulated. A seventh-order multioperator scheme was used to solve the Euler equations linearized about the mean flow field in an axisymmetric turbulent jet. The mean field was computed using fifth-order compact approximations of the convective terms under conditions similar to experimental data. The numerical results were found to agree well with the experiment.     

Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl)(PMe3)3

The reaction of (ArN=)MoCl(2)(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe(3))(3) (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH(3); however, a slow H/D exchange and formation of (ArN=)Mo(D)(Cl)(PMe(3))(3) (2(D)) was observed upon addition of PhSiD(3). Reactivity of 2 toward organic substrates was studied. Stoichiometric reactions of 2 with benzaldehyde and cyclohexanone start with dissociation of the trans-to-hydride PMe(3) ligand followed by coordination and insertion of carbonyls into the Mo-H bond to form alkoxy derivatives (ArN=)Mo(Cl)(OR)(PMe(2))L(2) (3: R = OCH(2)Ph, L(2) = 2 PMe(3); 5: R = OCH(2)Ph, L(2) = η(2)-PhC(O)H; 6: R = OCy, L(2) = 2 PMe(3)). The latter species reacts with PhSiH(3) to furnish the corresponding silyl ethers and to recover the hydride 2. An analogous mechanism was suggested for the dehydrogenative ethanolysis with PhSiH(3), with the key intermediate being the ethoxy complex (ArN=)Mo(Cl)(OEt)(PMe(3))(3) (7). In the case of hydrosilylation of acetophenone, a D-labeling experiment, i.e., a reaction of 2 with acetophenone and PhSiD(3) in the 1:1:1 ratio, suggests an alternative mechanism that does not involve the intermediacy of an alkoxy complex. In this particular case, the reaction presumably proceeds via Lewis acid catalysis. Similar to the case of benzaldehyde, treatment of 2 with styrene gives trans-(ArN=)Mo(H)(η(2)-CH(2)═CHPh)(PMe(3))(2) (8). Complex 8 slowly decomposes via the release of ethylbenzene, indicating only a slow insertion of styrene ligand into the Mo-H bond of 8.     

Cascade cyclization of 1,2-diamino-4-phenylimidazole with aromatic aldehydes and cyclohexanediones

The three-component condensation of 1,2-diamino-4-phenylimidazole with aromatic aldehydes and 1,3-cyclohexanediones occurred regioselectively and afforded 3-amino-1-phenyl-10-aryl-7,8-dihydroimidazo[1,5-b] cinnolin-9(5H,6H,10H)-ones.     

Main stages of unusual allyl coupling involving nickel bis-η3-allyl complexes in the presence of dichlorobutenes

The reactions of nickel bis-η³-allyl complexes with dichlorobutenes were studied. The overall process includes several stages, each characterized by substantially different reactions: traditional allyl coupling, substrate insertion between recombining allyl ligands, and the trimerization of allyl fragments accompanied by hydride transfer (unusual allyl coupling). Unusual allyl coupling occurs at a final stage preceded by the formation of oligomeric nickel intermediates with the mean composition Ni₄(C₃H₅)₆(C₄H₆)₃Cl₇. Their decomposition gives nonadiene and nonatriene isomers and propene. Trace amounts of molecular hydrogen were found indicating the formation of nickel hydride complexes at the final stage. Nickel bis-η³-allyl complexes react similarly with different dichlorobutenes.     

New splitting methods for two-dimensional evolutionary equations

New second- and third-order splitting methods are proposed for evolutionary-type partial differential equations in a two-dimensional space. These methods are derived on the basis of diagonally implicit methods applied to the numerical analysis of stiff ordinary differential equations. The splitting methods are found to be absolutely unconditionally stable. Test calculations are presented.     

Friction in an elastohydrodynamic contact

The problem of the movement of a fluid in an elastohydrodynamic contact is examined in cases of high pressures, high displacement velocities, and low characteristic times, taking into account the nonlinear properties of the fluid — dependence of viscosity on pressure, temperature, and displacement velocity. Simple asymptotic formulas are obtained. The problem is solved numerically in the one-dimensional case. A comparison is made with an experiment on the measurement of the frictional force in an elastohydrodynamic contact.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 135–137, July–August, 1976.The authors wish to thank V. D. Danilova and A. I. Petrusevich for supplying the experimental data.     

Deformable-Drop Dynamics near an Airfoil Surface in Viscous Air

A locally monodisperse air-supercooled water drop flow past an airfoil is studied. The influence of the viscous boundary layer on the force exerted on the drops by the carrier gas and the effect of deformation of the drops on (i) their trajectories, (ii) the water mass flux density over the airfoil surface, and (iii) the wetted-surface length are considered. The effect of an airfoil electrostatic field on the dynamics of charged atmospheric drops is estimated. The role of the governing parameters, i.e. the airfoil angle of attack, the radius of the undisturbed spherical drop, and the drop charge is investigated.The possible origins of the discrepancy between the numerical and experimental results of foreign researchers are indicated.     

Statistical Modeling of Water Structure in a Near-Electrode Layer

The structure of water near the electrode surface is studied by a molecular dynamics method, the electrode is assumed to be a structureless conducting surface, a cell of 216 water molecules is used. It is shown that the structure of water in a near-electrode area formed under the electric field influence differs greatly from that in the bulk. The effect of anisotropy of water structure normally to the surface is found. The effect consists of a lower diffusion mobility of molecules in this direction, quantitatively depends on the surface charge density, and decays with increasing distance from the surface. The main role in forming the water structure in the near-electrode layer is played by electrostatic interaction.     

Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

A correlation between the energies of electronic singlet transitions in benzodiazepines and their biological activity, which was revealed earlier by means of negative ion mass spectrometry with resonance electron capture, has been verified with a UV absorption spectroscopy investigation. Also, it has been noted that the energies of electronic singlet transitions in benzodiazepines are close in value to the ionization energies of atoms Cs, Rb, K, Na, Li and Tl, the cations of which are known to play an important role in nerve cell excitation processes. Copyright 1999 John Wiley & Sons, Ltd.