The reaction mechanism for the N2H4 homogeneous oxidation in aqueous solutions is more complex than its heterogeneous electrochemical oxidation on the electrode surfaces. Homogenous oxidation of a mixture of non-labeled (14N2H4) and 15N-labeled (15N2H4) hydrazine in aqueous solutions produces 14N15N, indicating the intermediate existence of N4H6 or N4H4 intermediates with subsequent hydrogen transfers and splitting lateral N & horbar;N bonds. To explain the key part of the hydrazine oxidation reaction, the structures, thermodynamics, and electron characteristics of N4H4 in aqueous solution are investigated. Unlike N4H6, we have not found any spontaneous splitting of the bond between the lateral nitrogens in N4H4. The most probable products of N4H4 disproportionation are H2N & horbar;NH2 and N2, which are obtained by splitting the bond between the central nitrogen atoms, and so only 15N2 and 14N2 molecules are formed. Additionally, the formation of H3N & horbar;NH and N2 products is also preferred to structures without N & horbar;N fissions. The formation of H2N & boxH;N and HN & boxH;NH is energetically less advantageous. Cyclo-N4H4 structures are stable, without any N & horbar;N fissions, but their energies indicate their vanishing abundance in aqueous solution, so their involvement in hydrazine oxidation is highly improbable. Unlike N4H6, the oxidation of hydrazine to 14N15N molecules cannot be explained by N4H4 intermediates.

Oxidation of a mixture of nonlabelled (14N2H4) and 15N labeled (15N2H4) hydrazine in aqueous solutions produces 14N15N molecules, indicating the intermediate existence of N4H6 or N4H4 dimers with subsequent transfers of H atoms and splitting of lateral N-N bonds. To explain the key part of hydrazine oxidation reaction, the structures, thermodynamics, and electron characteristics of N4H4 molecules in aqueous solution are investigated at CCSD/cc-pVTZ level of theory. We have not found any spontaneous splitting of the bond between lateral nitrogen atoms in tetrazenes N4H4 during geometry optimization. The most probable N4H4 oxidation products are H2N-NH2 and N2, which are obtained by splitting the bond between central nitrogen atoms and so only 15N2 and 14N2 molecules are formed. Additionally, the formation of H3N-NH and N2 oxidation products is also preferred to structures without any N-N fissions. The formation of H2N=N and HN=NH reaction products is energetically less advantageous. Cyclo-N4H4 structures are stable, without any N-N fissions, but their very high Gibbs energies indicate their vanishing abundance in aqueous solution, so their involvement in hydrazine oxidation is highly improbable. Hydrazine oxidation to 14N15N molecules cannot be explained by tetrazene N4H4 intermediates.

The geometry of trans-HN=NH, cis-HN=NH and N=NH2 containing no, one or two 15N labeled atoms was optimized. The corresponding infrared vibrations were evaluated using a linear scaling factor. For each of these compounds at least one vibration can be found, which enables to distinguish between heteroisotopic 14N=15N and homoisotopic 14N=14N or 15N=15N species. Independent of the 15N labeling, only trans-conformation should be found in the reaction mixture under equilibrium conditions.

(E)-3-(1-Benzofuran-2-yl)propenoic acid (I) was prepared from 1-benzofuran-2-carbaldehyde under the Doebner’s conditions. The obtained acid was converted to the corresponding azide II, which was cyclized by heating in diphenyl ether to [1]benzofuro[3,2-c]pyridin-1(2H)-one (III). This compound was aromatized with phosphorus oxychloride to chloroderivative IV which was reduced with zinc and acetic acid to the title compound V. [1]Benzofuro[3,2-c]pyridin-2-oxide (VI) was synthesized by reaction of V with 3-chloroperoxybenzoic acid in dichloromethane. Treatment VI with benzoyl chloride and potassium cyanide (Reissert-Henze reaction) was shown to produce the corresponding [1]benzofuro[3,2-c]pyridin-1-carbonitrile (VII). The title compound was used for preparation of complex compounds VIII, IX

Oxide ceramics with pyrochlore structure such as Laa(2)Zr(2)O(7) are promising materials for advanced multifunctional applications including extreme environment, such as space applications. They combine low thermal conductivity, suitable coefficient of thermal expansion to join supporting materials and have optical response in the UV-VIS region with up-converting and down-converting properties after doping, required for coating, sensors, and electro-optic applications. The effect of doping elements such as Er3+& nbsp;and Yb3+, replacing isomorphically lanthanum in the Laa(2)Zr(2)O(7) with pyrochlore cubic structure, on material photophysical properties was investigated by selective doping, in the molar ratio of Er3+/Yb3+ ranging from 0.5 to 5. The reflectance spectra of materials prepared by sol-gel co-precipitation method after sintering at 1400 ?, investigated in the UV-VIS-NIR range showed as expected well resolved absorptions due to the 4f-4f intra-configurational transitions. At the same time, dielectric properties of sintered samples were investigated by terahertz time domain spectroscopy. The refractive indices observed in the range of-4.46-5.15, indicate high dielectric permittivity at THz frequencies applicable in energy storage materials or THz communication components. For all samples a broad absorption band was found in the THz region and the band intensities were clearly associated with the doping amount of Er and Yb cations into the Laa(2)Zr(2)O(7) structure, at frequencies 0.75-1.02 THz. Significant correlation at the level of R-2 = 0.911 was found between the absorption band corresponding to the 4I15/2 & RARR; 2H11/2 transition at 520.5 nm and the integrated intensities of THz bands. Dielectric ceramic materials such as titanium-, tantalum and niobium-oxide based ceramics have permittivity in the range 20-30. The permittivity of studied Laa(2)Zr(2)O(7) was-20 and increased after doping by Er3+/Yb3+ to-21-26.

The conformers of push–pull 3-[(2,2-dimethylhydrazinyl)methylene]-pentane-2,4-dione (CH3)2NNHCHC(COCH3)2 (DMHMP) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by ab initio calculations at MP2 and DFT B3LYP levels in various basis sets. The NMR spectra were obtained in chloroform and dimethylsulfoxide and the IR and Raman spectra of DMHMP as a solid and as a solute in various less and more polar solvents at room temperature have been recorded.DMHMP was prepared as a pure solid and the data from X-ray analysis revealed that DMHMP exists in solid state as EZa conformer with an intramolecular hydrogen bond. The geometries and relative energies of possible conformers of DMHMP were evaluated at the both levels of theory in several basis sets and compared with the data from X-ray analysis.According to the NMR spectra the studied compound exists as a single entity. On the other hand vibrational spectra revealed that in less polar DMHMP solutions the presence of the second less polar ZZa conformer is possible, whereas in more polar solvent only one EZa conformer is observed. The influence of the environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model. The observed IR and Raman bands were compared with calculated MP2/cc-pVTZ harmonic vibrational frequencies and assigned on the basis of potential energy distribution.

The isomers and conformers of push–pull 3-fluorophenylamino-2-acetyl propenenitrile (FH4C6)NHCHC(CN)(COCH3) (FPAAPN) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by ab initio calculations at MP2 and DFT B3LYP levels in various basis sets. The IR and Raman spectra of FPAAPN as a solid and as a solute in various solvents have been recorded. The NMR spectra were obtained in chloroform, acetone, acetonitrile and dimethylsulfoxide at room temperature.FPAAPN was prepared as a pure Z-isomer with an intramolecular hydrogen bond. According to the NMR spectra in chloroform the studied compound exists as a single ZZa entity. On the other hand, in more polar solvents the isomerization process occured and an additional EZa confomer was detected. The influence of the environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model.The observed IR and Raman bands were compared with calculated MP2/6-311G∗∗ harmonic vibrational frequencies and assigned on the basis of potential energy distribution.

In the memory of Prof. Ing. Ladislav Valko, DrSc. (1930–2013) A room-temperature synthesis of copper(II) 2-pyridylmethanolate tetrahydrate, [CuL2] · 4H2O, with nearly quantitative yields with its structure redetermined at 213 K is presented. In agreement with the X-ray structure data, the DFT quantum-chemical calculations confirmed the planar structure of CuL2 (C 2h symmetry). The measured IR and Raman spectra were interpreted using the DFT calculations and some erroneous assignments in the previous studies have been corrected.

The isomers and conformers of four push–pull compounds: methyl-2-cyano-3-methoxyacrylate (MCMA) H3COCHC(CN)(COOCH3), methyl-2-cyano-3-aminoacrylate (MCAA) H2NCHC(CN)(COOCH3), methyl-2-cyano-3-methylaminoacrylate (MCMAA) H3CNHCHC(CN)(COOCH3) and methyl-2-cyano-3-dimethylaminoacrylate (MCDMAA) (H3C)2NCHC(CN)(COOCH3) have been studied experimentally by vibrational and NMR spectroscopy and theoretically by the ab initio calculations at MP2 level in 6-311++G** basis set. The IR and Raman spectra of all compounds as a solid and solute in various solvents have been recorded in the region 4000–50cm−1. The NMR spectra were obtained in chloroform, acetonitrile and DMSO at room temperature.Because both electron-withdrawing groups are different, all studied compounds can exist as E and Z isomers and then conformational possibilities are given by the rotation of the methylester and methoxy or methylamino groups. NMR spectra revealed that both MCMA and MCDMAA compounds without the possibility of intramolecular hydrogen bonding were prepared as a pure E isomer whereas in the case of the compounds with the possibility of intramolecular bonding MCAA and MCMAA a mixture of both E and Z isomers was obtained.X-ray analysis shows the presence of two EZ and EE conformers in solid MCMA. For this compound the possible second conformer was detected by NMR in more polar solvent DMSO. Vibrational spectra revealed the existence of two EZa and EEa conformers with Z and E orientation of methylester group and with anti orientation of dimethylamino group for MCDMAA. For MCAA and MCMAA the Z isomer with Z orientation of methylester group and with intramolecular hydrogen bond is the most stable one. In more polar surrounding (DMSO) the isomerization of ZZ or ZZa conformers of MCAA and MCMAA, respectively to E isomers occurred. These experimental findings have been supported by ab initio solvent effect calculations.

2-Methyl[1]benzofuro[3,2-c]pyridin-1-one 2 was obtained by reaction of the pyridone 1 with NaH followed by methylation with methyl iodide. The reaction of 1 with excess of P4S10 rendered the corresponding thione 3, which was methylated in PTC conditions giving 1methylsulfanyl[ 1]benzofuro[3,2-c]pyridine 4. The reactions of 1-chloro[1]benzofuro[3,2c] pyridine 5 with excess of heterocyclic secondary amines (piperidine, morpholine and pyrrolidine) gave 1-substituted [1]benzofuro[3,2-c]pyridines 6-8. Suzuki coupling reactions were realized with chloro-derivative 5 and phenylboronic or pyridine-3-boronic acids when 1phenyl[ 1]benzofuro[3,2-c]pyridine 9 or 1-(pyridin-3-yl)[1]benzofuro[3,2-c]pyridine 10 were obtained. 2-Amino[1]benzofuro[3,2-c]pyridin-2-ium 4-methylbenzene sulfonate 12 was prepared by N-amination of [1]benzofuro[3,2-c]pyridine 11 with 1-[(aminooxy) sulfonyl]-4methylbenzene. Then 12 was transformed into an unisolated zwitterionic N-imide 13, which afforded by 1,3-dipolar cycloaddition reactions with dimethyl but-2-ynedioate (DMBD) or ethyl propiolate the corresponding 1-benzofuro[3,2-c]pyrazolo[1,5-a]pyridine carboxylic acid-esters 14, 15. The reaction of 11 with benzoylnitromethane and DMBD gave benzoyl dimethyl ester 16. The structures of all new compounds were proved by IR and H-1 and C-13 NMR spectra and the structure of 1-phenyl[1]benzofuro[3,2-c]pyridine was proved by X-ray analysis.

Electrochemical and spectroscopic (EPR, UV-Vis, IR) studies of the aromatic secondary amines N,N'-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-N'-isopropyl-p-phenylene diamine (IPPD), N-phenyl-N'-(alpha-methylbenzyl)-p-phenylenediamine (SPPD) and N-phenyl-N'-(1,3-dimethyl-butyl)-p-phenylenediamine (6PPD), which represent the most important group of antioxidants used in the rubber industry, are presented. During oxidation, all the compounds show reversible redox couples in acetonitrile/0.1 M TBABF(4). The first oxidation potential depends substantially on the R substituent at the -N'H- moiety. Very similar UV-VIS spectra of monocation radicals and dications for all the compounds were observed by applying anodic oxidation as well as oxidation by tert-butyl hydroperoxide both in air and in inert atmosphere. The samples with N'-bonded aliphatic carbon in the molecule (e.g. IPPD) heated in air undergo consecutive chemical reactions leading to the formation of -N'=C- group. By the use of RO(2)(center dot) radicals only very low concentration of nitroxide radicals was obtained. Very high concentration of nitroxide radicals was achieved using 3-chloroperbenzoic acid. In the oxidation of investigated aromatic secondary amines with powder PbO(2) no EPR spectra were observed and UV-Vis and IR studies indicate the rapid formation of the final dehydrogenated oxidation product. (C) 2009 Elsevier Ltd. All rights reserved.

The IR, Raman and NMR spectra of 3-N,N-dimethylhydrazino-2-acetyl propenenitrile (DMHAP) [(H3C)2NNHCHC(CN)(COCH3)] were measured. X-ray analysis revealed that DMHAP exists in solid state as ZZa conformer. Vibrational and NMR spectra confirmed the existence of only one ZZa conformer with an intramolecular hydrogen bond in less polar solvents and next two EZa and EZs conformers of E-isomer with Z-orientation of acetyl group and anti and syn orientation of dimethylhydrazino group in more polar environments. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and DFT/B3LYP methods in 6-31G∗∗ basis set, and assigned on the basis of potential energy distribution.In addition, the geometries and relative energies of the possible isomers and conformers of DMHAP were also evaluated on the same levels and compared with the X-ray data. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model.

In the title compound, C(6)H(9)NO(4), which is an example of a push-pull alkene, N-H⋯O inter-actions stabilize the crystal structure.

Using B3LYP/6-31G* treatment, the optimal geometries and IR spectra of N,N´-diphenyl-p- phenylenediamine antioxidant (DPPD) and of N,N´-diphenyl-p-quinonediimine (DQDI) as its double dehydrogenated oxidation product have been obtained. The complete conformation analysis predicts the existence of four stable conformers of each of the systems under study. Experimental IR spectra of DPPD sample heated on air at 140 ºC confirmed the DQDI formation even at increased temperatures.

The IR and Raman spectra of aminomethylene-malonic acid dimethylester (AMDME) [NH2CHC(COOCH3)2] and its N-methyl derivatives (MAMDME and DMAMDME) were measured in solid phase and in different solvents at various temperatures. X-ray analysis revealed that AMDME exists in solid phase as EZ conformer, MAMDME as ZZa conformer and DMAMDME as ZE conformer (the first and second E or Z letters express the orientation of the carbonyl oxygen to the CC double bond for trans and cis methylester group, respectively, and the third letter a denotes anti position of methylamino group with respect to the CC double bond). In less polar solutions dominantly two ZZ and EZ conformational forms of AMDME and ZZa and EZa of MAMDME are observed, whereas in more polar environments a third conformational form (ZE and ZEa, respectively) also appeared.The behaviour of DMAMDME is different because there is no intramolecular hydrogen bond and in less polar solutions exists in two ZZ and ZE conformational forms. Very weak indications of a third conformational form (probably EZ conformer) were observed only in more polar surroundings. From the solution IR temperature dependent spectra the energy difference between ZE and ZZ conformers of ΔH=1.8±0.5kJmol–1 in chloroform and ΔH=4.2±0.5kJmol–1 in acetonitrile was estimated with the ZZ one being more stable.The geometries and relative energies of the possible conformers of all three compounds were evaluated using ab initio MP2 and DFT B3LYP methods in 6-31G∗∗ basis set with PCM solvent effect inclusion. The influence of environment polarity on the conformational equilibrium is discussed.

2-[3-(Trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (I) was prepared by a three-step synthesis. Its reaction with phosphorus sulfide rendered thione II which was methylated to 2-[3-(Trifluoromethyl)phenyl]-4-methylsulfanylfuro[3,2-c]pyridine (III). 5-Methyl-2-[3-(trifluoromethyl)phenyl]-4,5-dihydrofuro[3,2-c]pyridin-4-one (IV) was obtained by the reaction of I with methyl iodide in PTC conditions. The chlorine atom in derivate V was replaced with heterocyclic secondary amines via nucleophilic substitution and 4-substituted furopyridines VIa and VIb were thus prepared. 2-[3-(Trifluoromethyl)phenyl]furo[3,2-c]pyridine-4-carboxylic acid (VII) was obtained by hydrolysis of the corresponding carbonitrile Va.

In the title compound, C5H6N2O2, which is an example of a push-pull olefin, a network of N-H center dot center dot center dot O and N-H center dot center dot center dot N interactions helps to establish the crystal packing. The length of the nominal olefinic C = C bond is 1.385 (2) angstrom.

The isomers and conformers of two push–pull hydrazines: 3-N,N-dimethylhydrazino-2-acetyl propenenitrile [(H3C)2NNHCHC(CN)(COCH3)] (DMHAP) and 3-N,N-dimethylhydrazino-2-methylsulfonyl propenenitrile [(H3C)2NNHCHC(CN)(SO2CH3)] (DMHSP) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by the ab initio calculations at MP2 level in 6-31G** basis set. The IR and Raman spectra of both compounds as a solid and solute in various solvents have been recorded. The NMR spectra were obtained in chloroform and DMSO at room temperature.

In the title compound, C6H11N3O2S, which is an example of a push-pull olefin, a network of N-H center dot center dot center dot O, C-H center dot center dot center dot O and C-H center dot center dot center dot N interactions help to establish the crystal packing.

Summary Acrylamide was applied onto two additives of table salt - potassium ferrocyanide and potassium iodate - and heated in a glass reaction vessel within temperature range 102–180 °C with heating rate of 2 °C.min -1 to study the effect of these inorganic salts on acrylamide elimination. For comparison, the same experiment was carried out also with chemically pure sodium chloride. As found, the amount of acrylamide applied onto chemically pure sodium chloride decreased only by 13%, while the amounts of acrylamide applied onto potassium ferrocyanide and potassium iodate decreased much more considerably - by 61% and 88%, respectively. Comparing infrared spectra of pure acrylamide and the product formed during the experiments, it was found that all the salts under study brought about the polymerization of acrylamide through the formation of C-C backbone polymer while the carbonyl and amino groups remained unchanged. As concluded, potassium ferrocyanide and potassium iodate exhibit a much stronger effect on acrylamide polymerization than pure sodium chloride itself. For this reason, they could strengthen considerably the efficiency of acrylamide elimination in a real food matrix with regard to their presence in table salt, or being added directly to the thermally treated food matrix, respectively.