Mass-spectrometer investigation of 3, 6-dialkyl-2, 5-diketopiperazines

Analysis of mass-spectra of various 2, 5-diketopiperazines gives the basic fragmentation rules for their molecular ions, and the effects of nature and positions of substituents on the process.Mass-spectrometry Laboratory of the Institute of the Chemistry of Natural Compounds.Antibiotics Chemistry Laboratory of the Institute of the Chemistry of Natural Compounds.     

The multidipole effect in reactions of polyfunctional peroxy radicals

Conclusions The rate constant of the reaction of peroxide radicals of acrylic and methacrylic esters of polyols with nonpolar cumene is not dependent on the number of ester groups, and with polar 2,4,6-tri-tert-butylphenol decreases with an increase in the number of ester groups in the peroxide radical. Both findings are in agreement with the model of a dipole-dipole interaction in reactions of polyfunctional compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 778–781, April, 1985.     

Isotonic and isobaric dependencies of nuclear charge radii for rare-earth nuclei

Isotonic and isobaric dependencies of nuclear charge radii in the region between Z=54 and Z=70 are obtained from the analysis of isotope shift data r² and muonic and electron scattering data on r². They are compared with the predictions of the droplet model and the Hartree-Fock calculations. The isobaric dependencies of r² have proven to be especially sensitive to the choice of an effective nucleon-nucleon interaction.     

Reaction of undecyl radicals with aromatic hydrocarbons

A competition method (R^.+O₂RO ₂ ^. , R^.+XHRH+X^.) is proposed to measure the relative rate constants for the interaction of alkyl radicals with different organic compounds. Partial (per C–H bond) rate constants have been determined for the reaction of undecyl radicals with cumene, ethylbenzene and toluene.

---

(R^.+O₂RO ₂ ^. , R^.+XHRH+X^.), . ( C–H ) , .

     

Equilibria Between Molecular and Ionic Complexes with an NH⋯N Hydrogen Bond. Fluorinated Aromatic Amine as a Proton Donor

Ultraviolet absorption spectra in the range 300-200 K were used to study the composition and structure of complexes formed in solutions by the fluorinated amine (4-CF3C6F4)2NH as a proton donor with dibutylamine. A program is developed for quantitative analysis of sets of the spectra of equilibrium multicomponent systems, that allow to find spectral and thermodynamic characteristics of the individual components. In the systems in study, 1:1 and 1:2 fluorinated diamine-dibutylamine complexes are formed. The first of them in a molecular complex with an NHN hydrogen bond, and the second is an ionic proton-transfer complex. The equilibrium constants between the complexes and the free molecules are found, the enthalpies and entropies of formation of both complexes are found, and the spectra of the complexes are measured.     

Kinetic isotope effect in proton exchange processes between methanol and water in inert solvents

The kinetic isotope effect in proton exchange between methanol and water in CCl₄ solution was studied by¹H and²H NMR and kinetic IR spectroscopy. The exchange rate increases in the series CD₃OH+H₂O3OD+H₂O3OD+D₂O. It has been concluded that the limiting step of the reaction involves the formation of an H-bonded cyclic intermediate.

---

¹H ²H - CCl₄. , CD₃OH+H₂O3OD+H₂O3OD+D₂O. , - -.