Effect of anchimeric assistance in the reaction of triphenylphosphine with α,β-unsaturated carboxylic acids

Quaternization of triphenylphosphine with maleic and cis-aconitic acids is strongly accelerated by participation of the cis-carboxyl group in stabilization of the phosphonium zwitterion intermediate by intramolecular hydrogen bonding, in spite of steric hindrance by the acid's reaction center. A similar effect for trans-isomeric acids is not observed, which can be rationalized on the basis of spatial structures of the generated zwitterions, implying an electrostatic interaction between the phosphonium center and carbonyl oxygen atom. The effect of anchimeric assistance decreases when the intramolecular hydrogen bonding disfavors attack of the phosphine on the sterically less hindered carbon atom of the C=C bond, as observed for cis-aconitic acid. © 2014 Wiley Periodicals, Inc

Electrical resistivity of liquid CuSn, CuSnBi, CuSnBiIn, CuSnBiInCd alloys of equiatomic compositions

The resistivity of liquid CuSn,CuSnBi, CuSnBiIn, CuSnBiInCd alloys of equiatomic compositions are measured using the rotating magnetic field method to obtain information on their liquid structures. The alloys of equiatomic composition we considered as the high-entropy alloys. The results are discussed in the frame of a microheterogeneous structure of a metallic melt. A conclusion is made about the character of the modification of temperature dependence of the resistivity of liquid alloy due this microheterogeneous structure. All the investigated alloys demonstrated the change in the temperature coefficient of the resistivity for heating and cooling. These changes determined the temperature of destruction the microheterogeneous structure of a metallic melt (T∗). The value of temperature T∗ for all alloys was 1070 K (800 °C). The change in the temperature coefficient of the resistivity of the alloys on heating to 1070 K (800 °C) is interpreted using the Nagel-Tauc model. © 2019 Author(s)

Mechanistic aspects of reactions of triphenylphosphine with electron-deficient alkenes in acetic acid solution

Kinetic data provide evidence that proton transfer to the carbanion centre of a phosphonium zwitterion is the rate-determining step in quarternization reactions of triphenylphosphine with electron-deficient alkenes in acetic acid solution. This conclusion is based on the third-order rate equation, the reactivity of the alkenes, and solvent isotope effects in deuteroacetic acid. Copyright © 2013 John Wiley & Sons, Ltd

Radiation-induced hydrogen transfer in metals

The paper presents processes of hydrogen (deuterium) diffusion and release from hydrogen-saturated condensed matters in atomic, molecular and ionized states under the influence of the electron beam and X-ray radiation in the pre-threshold region. The dependence is described between the hydrogen isotope release intensity and the current density and the electron beam energy affecting sample, hydrogen concentration in the material volume and time of radiation exposure to the sample. The energy distribution of the emitted positive ions of hydrogen isotopes is investigated herein. Mechanisms of radiation-induced hydrogen transfer in condensed matters are suggested

Phosphine-catalyzed addition of P(O)-H compounds to ethyl phenylpropiolate

© 2015 Elsevier Ltd. An efficient PBu3-catalyzed α-addition of the P(O)-H bond to ethyl phenylpropiolate has been developed. This strategy offers a facile method for the preparation of synthetically useful alkenyl phosphonates and phosphinates proceeding under neutral reaction conditions with high atom economy