Protophilic isotopic hydrogen exchange of 1-ferrocenyl-2-(nitrophenyl)ethylenes

cis-1-Ferrocenyl-2-(4-nitrophenyl)ethylene enters into the protium/deuterium exchange in basic medium at the expense of hydrogens of the phenyl ring, at ortho positions in respect of the nitro group. The homoaromatic analogue, 4-nitrostilbene, under the same conditions, undergoes isotopic exchange occurring exclusively at the vinylic CH fragment attached to the nitrophenyl group. The difference is eliminated as a result of the shift of the nitro group from position 4 into position 2 of the phenyl ring: cis-1-ferrocenyl-2-(2-nitrophenyl)ethylene enters into H⁺/D⁺ exchange in the same manner as 4-nitrostilbene. Correspondence to: Professor Z.V. Todres.     

Orientation in the nitration of 3-phenyl-4-substituted furazans

The nitration of 3-phenyl-4-substituted furazans with various nitrating agents was investigated. It is shown that the orientation of the nitro group that is incorporated in the phenyl ring is determined by the substituent in the 4 position of the furazan ring, whereas the introduction of a furazan substituent in the phenyl ring lowers the reactivity of the latter. The corresponding dinitro derivatives can be obtained by means of acid mixtures.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 27–29, January, 1982.     

Effets de substituants et conformation de stilbenes

Simultaneous study of para nitrostilbenes by X-ray diffraction and ¹³C nuclear magnetic resonance shows a quantitative relationship between the effect of a para nitro substituent on the chemical shift of ethylenic carbon not adjacent to the substituted phenyl ring and the dihedral angle between this phenyl ring and the central double bond. The alternative introduction of substituents in each phenyl ring discloses at the position of carbon β a certain π-polarization which extends to the double bond and to an unsaturated group carried by carbon α.     

Differentiation of positional isomers of nitro meso-tetraphenylporphyrins by tandem mass spectrometry

We studied by tandem mass spectrometry two isomers of nitro meso-tetraphenylporphyrin, one with a nitro group in the para position of a phenyl ring and the other with the same group in a beta-pyrrolic position, and their copper complexes. Collisional activation of the molecular ions of both free-base porphyrins and of their copper complexes produces an array of product ions that permit ready differentiation of the two positional isomers. The diagnostic ions, when the nitro group is in a beta-pyrrolic position, may be produced through intramolecular and double cyclization processes, triggered by the interaction of the nitro substituent with the neighboring meso-phenyl ring. These diagnostic ions do not form when the nitro group is in the para position. The gas-phase processes have precedents in solution chemistry.     

Theoretical Study on Second‐order Nonlinear Optical Properties of Substituted Thiazole Derivatives

On the basis of ZINDO program, we have designed a program to calculate the nonlinear second‐order polarizability β_yk and β_μ according to the SOS expression. The second‐order nonlinear optical properties of 4‐nitro‐4′‐dimethylamino‐stilbene and a series of its thiazole derivatives were studied. The calculated results were that: When replacing a benzene ring in 4‐nitro‐4′‐dimethylamino‐stilbene by a thiazole ring, the influence on β values depends on the position of thiazole ring. When the thiazole ring connects with nitro group (acceptor), the β values increase significantly compared with corresponding stilbene derivatives. The β values of 2‐(p‐donor‐β‐styryl)‐5‐nitro‐thiazole derivatives (2–7) are larger than those of 2‐(p‐nitro‐β‐styryl)‐5‐donor‐thiazole derivatives (8–13) and 2‐(p‐donor‐phenyl)‐azo‐5‐nitro‐thiazole derivatives (14–19). The 2‐(p‐donor‐β‐styryl)‐5‐nitro‐thiazole derivatives (2–7) are good candidates as chromophores duo to their high nonlinearities and potential good thermal stability.     

N—H...O and N—H...N interactions in three pyran derivatives

The three pyran structures 6‐methylamino‐5‐nitro‐2,4‐diphenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₅N₃O₃, (I), 4‐(3‐fluorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄FN₃O₃, (II), and 4‐(4‐chlorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄ClN₃O₃, (III), differ in the nature of the aryl group at the 4‐position. The heterocyclic ring in all three structures adopts a flattened boat conformation. The dihedral angle between the pseudo‐axial phenyl substituent and the flat part of the pyran ring is 89.97 (1)° in (I), 80.11 (1)° in (II) and 87.77 (1)° in (III). In all three crystal structures, a strong intramolecular N—H...O hydrogen bond links the flat conjugated H—N—C=C—N—O fragment into a six‐membered ring. In (II), molecules are linked into dimeric aggregates by N—H... O(nitro) hydrogen bonds, generating an R₂²(12) graph‐set motif. In (III), intermolecular N—H...N and C—H...N hydrogen bonds link the molecules into a linear chain pattern generating C(8) and C(9) graph‐set motifs, respectively.     

Molecular structures of mononitroanilines and their thermal decomposition products

The molecular structures of 2-nitro, 3-nitro, and 4-nitroaniline and their internal rotational isomers were calculated by anab-initio method using HF/6-31G* basis set. The geometries were influenced by the nitro group's position. The perturbation of the amino group on the nitro group was observed in a 2-nitroaniline isomer having a molecular structure distinct from that of the other two isomers. Among them, 4-nitroaniline is the most stable one. Internal rotation tests of either the nitro or amino group of 3-nitro and 4-nitroaniline indicate that no significant deformations of the phenyl ring occurred after internal rotation; however, the internal rotational isomers of 2-nitroaniline differed from its original structure. Relatively easier internal rotation of the nitro group than the amino group and different C-NO₂ and C-NH₂ bonds indicate the bond-breaking message of nitroanilines. As products of explosives induced by thermal or shock are of interest, five products of 2-nitroaniline were selected to assess their geometries and energies. The above calculations revealed that these products are thermodynamically unfavorable.     

Synthesis and nitration of 4-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one

Analysis of the UV spectra of the reaction products shows that in the nitration of 4-phenyl-2,3-dihydro-1H-1,5-benzodiazepin-2-one the nitro group is directed to the benzodiazepine ring rather than to the phenyl ring to give a 7-nitro derivative.Translated from Khimiya Geterotsiklieheskikh Soedinenii, No. 4, pp. 525–528, April, 1977.     

Diazo liquid crystals for potential infrared applications

Nine series of liquid crystals containing an electron-donating group at one end of a conjugated system and an electron-withdrawing group at the other end have been synthesized. The electron-donating group is 4-n-alkylpiperazine and the electron-withdrawing group is the nitro group; and the conjugated system is diphenyldiazene with zero, one or two substituents on the phenyl ring not containing the nitro group. The substituents are-F,-Cl, and-CH₃. Most of the compounds synthesized are nematogenic and exhibit rather broad liquid crystalline ranges. The effects of the lateral substituents on the optical absorption and phase transition temperatures are correlated with their nature and position of substitution. Dielectric anisotropy and birefringence measurements were made using mixtures containing 10 wt % of synthesized liquid crystals dissolved in commercial mixture E7.     

A theoretical study of the structure and vibrations of 2,4,6-trinitrotolune

Theoretical calculations of the structure, internal rotations and vibrations of 2,4,6-trinitrotolune, TNT, in the gas phase were performed at the B3LYP/6-31G* and B3LYP/6-311+G** levels of theory. Two genuine energy minimum structures were found. In both structures the 4-nitro group is planar to the phenyl ring, while the 2,6-nitro groups are slightly out of plane with the phenyl ring due to steric interaction with the methyl group. The two structures are related by internal rotations of the methyl and 2, or 6-nitro group. The lowest energy route for interconversion between them is a concerted motion of the methyl group and 2 or 6 nitro group in a ‘cog wheel’ type of mechanism. The geometry of the low energy structure A is closest to that observed in the crystal structures of TNT, where all three nitro groups are out of plane with the phenyl ring. FTIR and Raman spectra of solid TNT and ¹³C, ¹⁵N enriched TNT are presented and assigned with the help of the B3LYP/6-311+G** calculations on A. The lower level B3LYP/6-31G* calculation fails to predict the correct vibrational coupling between the nitro and phenyl groups. The B3LYP/6-311+G** calculation gives a good prediction of the nitro vibrations and the isotopic shifts observed for TNT isotopomers.     

Diazo liquid crystals for potential infrared applications

Nine series of liquid crystals containing an electron-donating group at one end of a conjugated system and an electron-withdrawing group at the other end have been synthesized. The electron-donating group is 4-n-alkylpiperazine and the electron-withdrawing group is the nitro group; and the conjugated system is diphenyldiazene with zero, one or two substituents on the phenyl ring not containing the nitro group. The substituents are-F,-Cl, and-CH₃. Most of the compounds synthesized are nematogenic and exhibit rather broad liquid crystalline ranges. The effects of the lateral substituents on the optical absorption and phase transition temperatures are correlated with their nature and position of substitution. Dielectric anisotropy and birefringence measurements were made using mixtures containing 10 wt % of synthesized liquid crystals dissolved in commercial mixture E7.     

Electronic effects in dianion radicals of nitro derivatives of 2-phenylbenzimidazole

The EPR spectra of the dianion radicals of 5(6)-nitro-2-(4-aminophenyl)benzimidazole (I), 5(6)-nitro-2-phenylbenzimidazole (II), 5(6)-nitro-2-(4-nitrophenyl)benzimidazole (III), 5(6)-nitro-2-(3-nitrophenyl)benzimidazole (IV), and 2-(4-nitrophenyl) benzimidazole (V), obtained by electrochemical reduction in dimethylformamide (DMF) in a Bu₄NClO₄ -base electrolyte in the presence of Bu₄NOH (VI), were studied. Under the influence of VI, these compounds split out a proton from the imidazole ring and give anions I–V, which are capable of adding an electron reversibly. It was shown that the unpaired electron in I and II is localized in the benzimidazole system and that the splitting of the nitrogen atom of the nitro group does not depend significantly on the substituent in the phenyl ring. The introduction of a nitro group in the phenyl ring (III–V) leads to localization of the unpaired electron on it. The nature of the substituent in the benzimidazole system has a significant effect on the splitting constant for the nitrogen atom of the nitro group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 530–531, April, 1979.We thank T. A. Maslennikova for kindly providing us with the compounds for the investigation.     

New five‐ring symmetrical bent‐core mesogens exhibiting the fascinating B7 phase

Three new homologous series of symmetrical five‐ring bent‐core compounds have been synthesized and investigated for their mesomorphic properties. The laterally unsubstituted parent compounds exhibit a metastable SmCP_A phase. However, the two series of compounds containing a strongly polar cyano or nitro group at the angular position of the central phenyl unit show the fascinating classical B₇ phase. The mesophases have been characterized using standard techniques.     

Synthesis of 4-(2-hydroxyaryl)-3-nitro-4H-chromenes

A combinatorial library of 4-(2-hydroxyaryl)-3-nitro-4H-chromenes was synthesized in high yield by C4-SMe substitution in N-alkyl/phenyl 4-(methylthio)-3-nitro-4H-chromen-2-amines with a variety of phenols. The reaction always provided C2 substitution in the phenol ring, dictated by hydrogen bond interactions between the phenolic hydroxyl group and the nitro group in 3-nitro-4H-chromenes. Reduction of the nitro group with concomitant hydrolysis of the enamine in 4-(2-hydroxyaryl)-3-nitro-4H-chromenes with Zn, Ac₂O in AcOH furnished hybrid amino-acid lactone incorporating ortho-tyrosine and phenyl alanine moieties.     

The mass spectra of benzofuroxans—an example of an ortho effect

The fragmentation behavior of a series of nine benzofuroxans has been studied under electron impact conditions. It was found that benzofuroxans without a nitro group in the 4-position fragment principally through loss of N₂O₂ (the furoxan ring), whereas those with a nitro group ortho to the furoxan ring exhibit predominant loss of NO from position 1 of the furoxan ring.     

Structural Modification Influences the Characteristics of Langmuir Monolayers from Aromatic Carboxylic Acids

The molecular organization of purely aromatic, polyphenyl carboxylic acids, as Langmuir monolayers at the air/water interface, has been investigated by means of surface pressure and electric surface potential measurements upon film compression. The monolayer characteristics of the basic compound, a symmetrical triphenylbenzene (5'-phenyl-m-terphenyl) ring with a carboxylic group at the 4 position (namely 5'-phenyl-1,1' : 3',1"-terphenyl-4-carboxylic acid), are compared with those of its derivatives containing hydrophilic (nitro) or hydrophobic (phenyl) substituents. The nature of the substituent as well as its position (2' or 4') has a profound influence on the monolayer properties. The results are discussed in view of molecular orientation deduced from values of effective dipole moments. Copyright 2001 Academic Press.     

Orientation in the nitration of 2-pyridones

The ratio of 3- and 5-nitro isomers formed in the nitration of 2-pyridones with nitric acid is determined by the reaction temperature but is independent of the concentration of the nitrating agent. The presence of a phenyl group in the 6 position of the -pyridone ring hinders incorporation of a nitro group in the 5 position.Translated from Khimiya Geterotsikicheskikh Soedinenii, No. 1, pp. 72–75, January, 1978.     

Development of an improved synthetic route to an AB phenylquinoxaline monomer

The primary objective of this research was the development of an efficient synthetic route for a previously prepared self‐polymerizable PPQ monomer mixture, 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline and 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline. Thus, the intermediate, 4‐hydroxybenzil, was synthesized in good yield, starting from phenol with phenylacetyl chloride, followed by oxidation. The other intermediate, 4‐fluoro‐1,2‐phenylenediamine, was also less costly synthesized, starting from 2,4‐difluoronitrobenzene with ammonium hydroxide, followed by reduction, giving excellent yield. The overall monomer yield was superior to previous reports. Another research objective involved preparation of various monomer mixtures that could be synthesized even less costly, and attempts on polymerization could generate the same structure of PPQ from an original monomer mixture. Thus, the monomer mixture that had switched functional groups from the original one, 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐hydroxyquinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐hydroxyquinoxaline, was prepared. Various monomers with different functional groups attached on the 6‐position of the quinoxaline ring, such as chloro‐ and nitro‐substituted monomers instead of fluoro‐substituted ones, were also prepared. Several attempts to build up high molecular weights were not successful. In the case of the switched monomer mixture, weaker nucleophility and less activation on the fluorine atom were to be the reason in the switched monomer. In the cases of chloro‐ and nitro‐substituted monomers, poorer leaving power and side reactions were to be the reasons. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 801–814, 2005     

Dipole moments of some isoxazole derivatives

The dipole moments of isoxazole and 13 of its halo, amino, and nitro derivatives were measured. A method is proposed for vector calculation for estimating the direction of the dipole moment of the isoxazole ring. It is demonstrated that phenyl substituents in the 3 and 5 positions are electron donors with respect to the isoxazole ring. It was found that the dipole moments of 4-substituted 3,5-dimethylisoxazoles correlate satisfactorily with the Hammett constants.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 460–463, April, 1972.     

Free radicals in the electrochemical reduction of certain mononitro and dinitro derivatives of pyridine

In the primary process of electrochemical reduction of substituted 3-nitropyridines in dimethylformamide, their anion radicals are formed. This also takes place in the reduction of 3,5-dinitropyridines and 3-nitropyridines with a nitrophenyl substituent at position 2 or 4. For these dinitro derivatives, however, secondary free radicals are formed as well; in a basic medium, these are the products of reduction of the corresponding Meisenheimer complexes. Serving as the reaction center for electroreduction is the nitro group on the pyridine ring, not the group on the phenyl ring. For the mononitropyridines and dinitropyridines that were studied, free radicals of the nitropyridine type are formed as the primary species. The structure of the primary and secondary free radicals was established by analysis of the hyperfine structure of their ESR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1079–1087, August, 1993.