Acrylonitr1le anion-radical detection by infrared internal reflection spectra

The application of internal reflection spectroscopy to the study of interface boundary layers has been extended over cases in which unstable particles appear at the interface as a result of imposing a negative electrical potential on the germanium hemicylinder, used simultaneously as an optical prism in the internal reflection spectroscopic device and as an electrode. The appearance of the particles is detected by their internal reflection spectrum. The method has been applied in the case of the electrochemically induced polymerization of acrylonitrile. Two particles were found to be generated during electrolysis. They are assigned to the anionradical and to the di-anion of acrylonitrile.     

VUV generation by eighth-order nonlinearity in Hg vapour

Direct eighth-harmonic generation ( = 134.4 nm) of Nd-laser radiation has been studied experimentally in Hg vapour. An electric field produced by free electrons created by photoionization is shown to be reasonable for even-order harmonic generation in a centrosymmetric medium.     

Nonlinear Brönsted relationships and the α-effect of oximate ions in acyl* transfer reactions

A detailed extrathermodynamic analysis of the behavior of oximate ions (pK_a≈7–13) in reactions with various types of substrate was undertaken. For oximate ions with pK_a≥9.0, irrespective of the nature of the acyl group, the reactivity of the oximes tends toward that of the alcoholate ions, and their α-effect disappears. The reason for this is the unfavorable solvation effects of the solvent. Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 86–90, March–April, 1998.     

Comparison of Carboxamides Reactivity with Respect to Benzoyl Chloride and Diphenyl Chlorophosphate in Acetonitrile

For amides belonging to series RCONH₂ (I), RCONHMe (II), RCONHPh (III), and RCONMe₂ (IV) rate constants k₁ (l mol^-1 s^-1) were determined (in acetonitrile at 25°C) specifying the nucleophilic reactivity of the oxygen atom in amides toward benzoyl chloride and diphenyl chlorophosphate. The lack of substrate selectivity in the reactions in question was established. For equal values of inductive constants ^* of the R substituents the reactivity sequence of amides with respect to both substrates is the same (I >> IV > II, and III > II), and it does not follow the corresponding sequence of basicities. A conclusion was drawn that both groups of reactions proceed through cyclic transition states resembling reagents: six-membered with amides I and III, and five-membered with amides II and IV.     

Dendrimeric Gd(III) complex of a monophosphinated DOTA analogue: optimizing relaxivity by reducing internal motion

A marked increase of relaxivity has been observed upon rigidifying the internal frame of Gd-containing PAMAM dendrimers: the effect has been attained by either protonation of the dendrimer or by forming supramolecular adducts with cationic polyaminoacids.