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1. An x-ray diffraction study of benzoyl chloride phenylhydrazone was conducted. 2. The presence of a conjugated system in the molecule and very short intramolecular contacts, which, however, did not permit an unambiguous conclusion to be drawn on the intramolecular interactions, was established.

1. The basicity constants of substituted benzaldehyde (BDMH) and acetophenone (ADMH) dimethylhydrazones in anhydrous acetonitrile are determined. 2. The amine nitrogen atom is the center of protonation in the dimethylhydrazones. 3. The effect of the substituents in the benzene ring on the reaction center is weakened 1.6-fold in the acoplanar ADMH molecules as compared to the BDMH molecules.

1. The photoelectronic spectra of a number of organophosphorus compounds of the type of WPXYZ were obtained and interpreted for the first time. 2. The upper orbital is primarily localized on the pπ-orbitals of the W atom, participates in the bonding of WP, and has little conjugation with the orbitals of the unshared pairs of the substituents. Exceptions are nitrogen-containing substituents. 3. Series of atoms W with respect to decreasing influence on the ionization potentials of the UEP of the substituents XYZ were established: for nonnitrogen-containing substituents OP > SP > P, and for nitrogen-containing substituents SP > OP > P.

An increase in the resistance of the N-N bond to hydrogenolysis on Raney nickel in alkaline media is observed not only for 1,2,4-trisubstituted 3,5-dioxopyrazolidines but also for other types of 3,5-dioxopyrazolidines that are capable of enolization. 3,5-Dioxopyrazolidines that are capable of forming betaines also do not undergo hydrogenation in neutral ethanol. The use of the potentiometric method of Sokol'skii and Druz′ made it possible to establish very slight adsorption of the enolates and betaines on the catalyst surface. The decrease in adsorbability is explained by a decrease in the effective charges on the nitrogen atom of the heteroring; this is in agreement with the results of calculations of the enolate and enol by the Pariser-Parr-Pople method. An assumption regarding the greater aromatic character of the enolate as compared with the enol is expressed on the basis of a comparison of the bond lengths.

1. The IR and electronic absorption spectra and the chromatographic behavior of the diazo coupling products of 1,2-diphenyl-3, 5-dioxopyrazolidine have been examined. 2. A hydrazone structure with intramolecular hydrogen bonding has been assumed.

1. The IR absorption spectra of 24 semi- and thiosemicarbazones of certain aldehydes and ketones in the crystalline state in the region of 700–3700 cm−1 were obtained and interpreted. 2. It was concluded that the compounds studied exist in semi- and thiosemicarbazone structures in the solid state. 3. Several types of association of the investigated compounds by means of hydrogen bonds were proposed, mainly according to the type

1. On the basis of the data of the method of dipole moments, potentiometric titration, and vibrational spectroscopy, a flat s-trans-configuration of the azines of certain aromatic aldehydes was proposed. 2. The values of pKa of symmetrical and nonsymmetrical benzalazines are determined by the interaction of the proton not only with one of the nitrogen atoms, but also with the entire conjugated azine fragment. .

1. The influence of the structure of the semi- and thiosemicarbazones on their reducibility is explained from the point of view of the contemporary representation of the structure of these organic compounds. 2. The semi- and thiosemicarbazones of fatty-aromatic compounds in weakly-acidic and neutral methanol solutions exist in a single form, which can transform to a sterioisomeric pair through the action of light. . 3. In weakly basic solutions of the derivatives of the fatty-aromatic ketones two waves are generally observed on the polarogram; the most probable cause of this is the formation of two tautomeric forms. .

1. The polarographic behavior of dimethylhydrazones and 1,2,4-triazolyl-4-imines of a number of benzaldehydes was studied in buffer solutions with a broad pH range. 2. A mechanism of the electrode process was proposed.

1. The high-resolution PMR spectra of azines, phenyl- and methylphenyl-hydrazones of aliphatic ketones and aldehydes were obtained and deciphered. 2. On the basis of an analysis of the data obtained, conclusions were drawn on the hydrazone structure of the compounds studied in the free state. 3. Using the data obtained and the theory of the magnetic anisotropy of aromatic rings, calculations were made of the probable configuration of the acetaldazine, dimethylketazine, acetone phenyl- and methylphenyl-hydrazones, and acetaldehyde methylphenylhydrazone molecules. 4. A study of the influence of temperature on the PMR spectrum of acetone methylphenylhydrazone within the interval from −14 to +80° indicated the absence of free rotation of the phenyl radical around the C-N bond.

The review surveys the present state of research on the conformation, isomerism, and intramolecular interactions of molecules of the immense class of organic compounds containing a hydrazone group. A list of 221 references is included.

1. A scheme of the mechanism of the so-called anamolous Fischer-Arbuzov reaction was proposed on the basis of a study of the products of catalytic decomposition of acetonephenylhydrazone in the presence of Cu2Cl2. 2. The decomposition of acetaldehydephenylhydrazone proceeds according to an analogous scheme and leads to the formation of 1-phenyl-5-methylpyrazoline. 3. A pyrazole is also formed in the case of acetophenonephenylhydrazone. 4. Aromatization of pyrazoline to pyrazole was accomplished, with elimination of hydrocarbon under the conditions of the reaction studied.

1. The polarographic behavior of 24 phenylhydrazones and methylphenylhydrazones in methanol-water solutions has been examined over the pH range 5.8–9.2. 2. The polarographic behavior of the tautomeric forms of these compounds—the hydrazonic, the enhydrazinic, and the azo form — has been compared with the behavior of model substances. The characteristic features in the polarographic behavior of the tautomers have been disclosed. 3. Some preliminary conclusions have been drawn on the reduction mechanism of the tautomeric forms on a mercury electrode.

1. The polarographic method was employed in a study of the tautomeric and stereoisomeric transformations in alcoholic solutions of the phenylhydrazones of acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone and benzaldehyde; the ethylphenylhydrazone of acetone was also studied. 2. It was shown that in alcoholic solution phenylhydrazones are generally capable of existing in three tautomeric forms, each of which in turns can be present as $yn- and anti-isomers. On dissolution in alcohol the tautomeric equilibrium Is shifted to the side of the azo form. 3. The half-wave potentials of the tautomers and stereoisomers of the various phenylhydrazones were determined, and the energies of the reciprocal transformations were calculated from the data obtained. 4. It was established that the phenylhydrazones of acetone, methyl ethyl ketone, methyl isopropyl ketone and cyclohexanone and the ethylphenylhydrazone of acetone possess the enhydrazone structure in the free state.

The polarographic behavior and semi- and thiosemicarbazones of acetic, butyric, isobutyric, and isovaleric aldehydes and the thiosemicarbazone of propionaldehyde was studied.

1. The dipole moments of phenyl and methylphenylhydrazones of a number of aldehydes and ketones, as well as benzeneazomethane and acetone hydrazone, were measured and calculated. 2. The hydrazone structure of all the compounds studied was confirmed, and the absence of tautomeric conversions of the phenylhydrazones in benzene solution was established.

The oscillopolarographic behavior of certain phenylhydrazones, semi- and thiosemicarbazones in buffered solutions was studied, and the possibility of oscillopolarographic monitoring of the conversions of aliphatic phenylhydrazones was demonstrated.

1. p-Nitrobenzaldehyde thiosemicarbazone and semicarbazone have quinonoid structures in an alkaline medium, and p-dimethylaminobenzaldehyde derivatives have quinonoid structures in an acid medium. 2. A study was made of the effect of S-methylation on the ultraviolet spectra of the thiosemicarbazones of benzaldehyde, acetophenone, cyclohexanone, and acetone. 3. It was shown that there is a hypsochromic shift of the absorption maximum as we pass to a polar solvent for some thiosemicarbazones and their S-methyl derivatives.

The chemical properties of organic compounds containing an open-chain hydrazono-group are surveyed systematically. A list of 412 references is included.

1. Benzalacetone, ethyl styryl ketone, isopropyl styryl ketone, and thiophene analogs of these compounds have a doublet of the carbonyl bonds associated with the existence of s-cis ⇌ s-trans conformational equilibrium. Benzalpinacoline and cinnamaldehyde exist chiefly in one conformation. There is a definite relationship between the volume of the alkyl substituent and the position of the conformational equilibrium. 2. The stretching vibrations of the C=O group in s-cis-conformers are in a higher-frequency region than s-trans-conformers. The opposite relationship is observed for the stretching vibrations of the C=C bonds. The difference between the stretching vibrations of C=O and C=C in the s-cis-conformation is greater than 72 cm−1, and in s-trans less than 70 cm−1.

The rate of hydrogenolysis of 3,5-dioxopyrazolidines at the N-N bond is determined by the number, position, and nature of the substituents in the heteroring. The introduction of a phenyl group into the 1 and 2 positions increases the rate of hydrogenation, while a phenyl group in the 4 position lowers it. On the other hand, an alkyl substituent in the 1 and 2 positions lowers the rate of hydrogenation, while an alkyl substituent in the 4 position increases it. It is assumed that the effect of substituents is a consequence of an increase or decrease in the adsorption of a molecule by the β-dicarbonyl or hydrazine fragments; this is in agreement with the results of calculation of the charges on the heteroring atoms. The hydrogenation of 4alkyl-1, 2-diphenyl-3,5-dioxopyrazolidines is limited by their activation, while the hydrogenation of the 4-phenyl derivative is limited by the activation of hydrogen.

By means of polarographic and microcoulometric methods it was shown that the reduction of semi- and thiosemicarbazones of acetophenone, p-chloroacetophenone and p-aminoacetophenone and also benzophenone semicarbazone at a dropping mercury electrode takes place irreversibly with participation of two electrons.

The dipole moments of eight α,β-unsaturated aromatic and heterocyclic aldehydes and ketones in dioxane solution were measured. The moments of the syn and anti conformations were calculated by vector-additivity schemes. The effect of the conformation on the moment of the C=O group was taken into account. The charge distribution was calculated by the Pariser-Parr-Pople method in order to estimate the polarization of the C=C bond.

CONTENTS I. Introduction 341 II. Investigation of structure and the effect of substituents on the reactivity of organic compounds 342 III. Detection of hydrogen bonds and chelate rings 347 IV. Study of tautomeric changes 348 V. Study of the stereoisomerism of organic compounds 351 VI. Study of the kinetics of chemical reactions 353 VII. Study of molecular rearrangements and reactions 356 VIII. Relation between polarographic data and those of other methods of investigation 357

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 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.

1. A study was made of the reaction of aromatic diazo compounds with the 4-ethylidene derivatives of 1, 2-diphenyl-3, 5-dioxopyrazolidine and it was shown that the hydrogen atoms in the methyl group of the latter compounds exhibit a high lability in the given reaction. 2. The electronic and IR spectra were discussed, as well as the Chromatographic behavior of the coupling products, and it was assumed that they have a hydrazone structure.

1. A study has been made of the polarographic behavior of semiand thiosemicarbazones of acetone, methyl ethyl ketone, methyl n-propyl'ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl n-amyl ke'tone, methyl n-hexyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and pinacoline semicarbazone. 2. It is proposed that the compounds investigated show a structure of ensemiand enthiosemicarbazine type in water-alcohol solutions. 3. The effect of alkyl groups on the ease of reduction of methyl alkyl ketone derivatives is explained from the point of view of present-day concepts in organic chemistry.

A number of products of the condensation of aminotriazole with substituted benzaldehydes were synthesized. Their UV spectra in ethanol and concentrated sulfuric acid are presented. The change in the UV spectra on passing from one solvent to another is explained by the change in the conjugation of the N-N bond. The basicities of the nitrogen atoms were compared by the Pariser-Parr-Pople method.

The UV, IR, and PMR spectra of a number of m- and p-substituted N-(benzylideneamino)-pyridinium iodides confirm the structure of hydrazonium compounds proposed for them previously. On the basis of physicochemical data, a hypothesis has been put forward of the participation of the pyridinium ring in an intramolecular interaction of the conjugation type. Charge-transfer bands are observed in the UV spectra of some of these compounds.