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1.In aprotic and limitedly protogenic media, electrochemical reduction takes place with the cleavage of the C-S bond (EEC mechanism) and in protogenic media with the hydrogenation of the C=C bond (ECE mechanism).2.The SO2 group does not prevent the distribution of the spin density over the whole molecule.

1.A study has been made of the electrochemical reduction of diazo compounds in aprotic media, and of chemical reactions accompanied by transfer of an electron to a molecule.2.The formation of primary and secondary anion-radicals has been demonstrated, the structures of these radicals were determined, and a study was made of the delocalization of the unpaired electron.

Conclusions 1.Study has been made of the electrochemical reduction of the salts of trans-1,2-diphosphonioethene on the dropping Hg electrode in protogenic and aprotic media.2.It has been shown that stable radical anions result from the first, reversible one-electron stage of the reduction of disalts in aprotic media. A scheme is proposed to describe the reduction mechanism.

1.2,5-Diaryl-1,3,4-oxadiazoles are reduced in dimethylformamide in two steps, the first of which is reversible and one-electron for diphenyl- and phenyl-p-nitrophenyloxadiazoles and two-electron for di-p-nitrophenyl- and di-m-nitrophenyloxadiazoles.2.Anion radicals of 2,5-diaryl-1,3,4-oxadiazoles were produced by electrochemical reduction at the potentials of the first wave, and the parameters of their ESR spectra were determined. In the case of the anion radical of di-m-nitrophenyl-1,3,4-oxadiazole, no equivalence of the two nitrophenyl fragments is observed. In the remaining symmetrically substituted oxadiazoles, delocalization of the unpaired electron over the entire chain of conjugation is observed.

Iminoxyl radicals involved in the homolytic oxidation of nitrolic acids, with the general formula (NO2)RC=NO., have been detected by means of ESR. In the presence of a strong acid, the ESR spectra of the radical (NO2)2C=NO. exhibits alternation of the line widths, owing to syn-anti isomerization.

1.Reduction of the azophosphonates proceeds in successive one-electron steps, the first of which is reversible.2.ESR methods have been used to show that azophosphonate anion-radical formation occurs in the first reduction step; an estimate of the spin density in these ions was obtained by these same methods. It has been shown that deuteration has an anomalous effect in delocalizing the unpaired electron in the diethylarylphosphonate anion radicals.

EPR and quantum chemical methods have been used to establish the nature of the distribution of spin density in electrochemically generated radical anions of diaryldiazocyanides. For the symmetrical diphenyldiazocyanides the unshared electron is distributed over the entire molecule, whereas the introduction of a bridge between the benzene rings leads to the localization of the unshared electron only on one fragment of the molecule.

1.Factors which determine the possibility of amino-nitrile cleavage of hydrazones on electrochemical reduction (ECR) include the basicity of the anionic product formed in the course of the ECR and the mobility of the aldehyde hydrogen which depends on the character of the electron polarization of the hydrazone fragment and the polarity of the N-N bond.2.The primary action in amino-nitrile cleavage under conditions of ECR is the deprotonation of the azomethine fragment in the unreduced molecule by electrochemically generated strong base (anion or dianion).

Conclusions 1.New phosphorus-containing iminoxyl radicals were obtained by the chemical or electro-chemical oxidation of phosphorylated oximes. ESR spectroscopy showed that these radicals exist as stable syn and anti isomeric forms.2.A dependence was shown for the coupling constants of the phosphorus atom on the geometry of the radical and the immediate environment of the phosphorus atom and the radical site.

1.Cation and anion radicals of unsaturated compounds whose molecules contain two phosphorus atoms have been generated electrochemically and their properties studied by ESR methods.2.These ion radicals are p-electron systems and in which the unpaired electron is delocalized over the P-C=C-P fragment. The stability of the ion radicals is discussed.

1.The formation and structure of primary and secondary unstable anion radicals was established by the ESR method in the electrochemical reduction of derivatives of nitrophenylhydrazines. The delocalization of the unpaired electron in the anion radicals was studied.2.A quantum chemical calculation of the distribution of spin density in these anion radicals was performed.

1.The stability of the O-glycosidic bond has been studied with O-glycosides of serine and its derivatives as examples over a wide pH range at various temperatures.2.In acid and neutral ranges of pH the stability of the O-glycosidic bond of serine is comparable with the stability of the O-glycosides of ordinary aliphatic alcohols. The free amino group of serine stabilizes the O-glycosidic bond under conditions of acid hydrolysis.3.In alkaline medium serine O-glycosides decompose according to aß-elimination mechanism, while serine O-glycosides decompose most readily when the serine functional groups are protected. The liberation of one of these or both simultaneously sharply increases the stability of the corresponding glycosides in alkaline medium.

The O-gluco- and O-galactopyranosides of serine methylamide and their dipeptide derivatives have been synthesized.

1.O-?-D-Glucosides of L-and D-serine methyl esters were synthesized by the glucosidation of N-(benzyl-oxycarbonyl)-L- and-D-serine methyl esters in presence of Ag2CO3, with subsequent removal of the protective groupings.2.In more concentrated solutions in presence of PbCO3 the corresponding ortho ester was formed.

1.A vacuum microcell with a three-electrode system for the electrochemical generation of unstable free radicals in the resonator of the spectrometer was proposed.2.Anion radicals of dimethyl esters of maleic and fumaric acids, cis- and trans-dibenzoylethylene were produced, and their EPR spectra were interpreted. The rapid and practically complete trans-iso-merization of the cis-anion radicals was demonstrated.3.Electrolysis at the potentials of the steps of reduction following the first leads to the formation of free radicals that are conversion products of the primary anion radicals. The structure of these products is discussed.

1.The mechanism of the polarographic reduction of nitrophenyldiethylarsines, their oxides and sulfides in aprotonic medium was studied. Schemes of the subsequent chemical reactions after the reception of a second electron by these systems were proposed.2.New organoarsenic anion radicals were produced by electrochemical reduction and investigated by the ESR method. Their stability was estimated. The delocalization of the unshared electron in them was studied, and possible causes of the appreciable decrease in the spin density on the arsenic atom in the transition from anion radicals with a tetra-to a tricoordinated arsenic atom were considered.

1.The mechanism of the electrochemical reduction of hydrazones of isomeric nitrobenzaldehydes in dimethylformamide solution and possible chemical reactions accompanying the transfer of an electron to a molecule were considered.2.The formation of primary and secondary unstable anion radicals was established, their structure was determined, and the delocalization of the unshared electron in them was studied.3.A quantum chemical calculation was made of the distribution of spin density in the anion radicals studied. A comparison of the data obtained with the experiment permits a rather accurate description of the hyperfine splitting from the nitrogen atom in the hydrazone group.

Conclusions The EPR spectra of some chemically and electrochemically generated phosphoniminoxyls were studied. The hyperfine coupling constants on the13C and15N nuclei were determined.

New phosphorus-containing iminoxyls in which the phosphorus atom is ? to the radical center were generated either electrochemically or photochemically, and the distribution of the spin density in them was established.

1.In the crystalline state the oximes ofa-phosphorylated aldehydes and ketones (I)–(VIII) represent mixtures of the syn- (dimers) and anti-isomers (trimers, chains) that are associated via hydrogen bonds at the oxime portion. Together with the syn- and anti-isomers, the formation of H bonds involving phosphoryl oxygen is possible in the acid chloride ofa-diphenylphosphinylpropiohydroxamic acid (IX).2.Equilibrium of the cyclic trimers (dominant form of H associates), dimers, and monomers occurs in relatively concentrated CCl4 solutions.3.Independent of the type of isomer, unassociated molecules predominant in dilute solutions as the conformer with a free hydroxyl group.

Conclusions 1.Arsinobenzoates are reduced in three steps, the first of which involves one electron and is reversible. The diethylarsinyl groups are electron acceptors. Transfer of a second electron leads to the rupture of the As-C bond and to the formation of methyl benzoate.2.The spin-density distribution in the arsinobenzoate radical anions has been studied.

Hydrazyl radicals are formed from triarylhydrazines either by UV irradiation or by electrochemical oxidation in the presence of bases. Here high resolution EPR spectra are observed, in which the hyperfine structure from all of the magnetic nuclei is manifested.

On the basis of an analysis of EPR spectra and quantum-chemical calculations, it was shown that a significant change of the hyperfine splitting a31P in phosphoniminoxyls during replacement of alkoxy groups at the phosphorus atom by alkyl groups is mainly governed by electronic factors of substituents at the phosphorus atom.

Double electron-nuclear resonance and triple electron-nuclear-nuclear resonance have been used for the first time to determine the HFS constants and their relative signs in free radicals and cation-radicals of phenoxazine, phenothiazine, and phenothiazine derivatives.

It was shown that the reaction of phosphorous hexaalkyltriamides withß-bromovinyl aryl sulfones proceeds via the step of electron transfer with the formation of ion-radicals.

Conclusions The HFS constants for the protons in positions 5–13 of the free radical 1,3-diphenyl-1, 4-dihydro-1,2,4-benzotriazin-4-yl were determined by the DENR method.

The oxidation of the products of the reaction of dialkylphosphorylacetaldehydes with aryldiazonium salts gives tetrazonyl radicals.

Summary The methyl ester of O-(ß-D-galactofuranosyl)-L-serine was synthesized for the first time by the ortho ester method.