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A series of C‐8 mono‐ and disubstituted isatylidenes were prepared in order to examine the influence of the substituent on the polarization of the ethylenic carbons C‐3=C‐8. Donor–acceptor C‐8 substitution resulted in an inversion of the polarization of the ethylenic carbons, as evidenced by the 13C NMR spectra, and because these compounds can exist in solution as equilibrium mixtures of the E‐ and Z‐isomers. The dual donor–acceptor character of the heterocycle is controlled by the cross‐conjugated C‐3=C‐8 double bond, in which the C‐3 carbon atom has the possibility of conjugating with either the donor or the attracting portion of the heterocyclic system, consistent with contributions from isatylidene resonance forms which induce the C‐8 carbon atom to be charged either positively or negatively, thus allowing an opposite sense of the push–pull effect. Copyright © 2000 John Wiley & Sons, Ltd.

The doping reactions of graphite oxide (GO) with 3-3′-diaminobenzidine (DAB) were studied using N, N′-dicyclohexylcarbodiimide (DCC), cyanuric chloride (CC) and hexafluorophosphate (HATU) as coupling agents. The bifunctionality of the coupling agents aid to interact GO functional groups with amino groups of DAB without being part of the final product. The doped materials (d-GO) and GO were characterized by thermogravimetric analysis, x-ray diffraction, FTIR/Raman spectroscopy, x-ray photoelectron, high-resolution electron microscopy and cyclic voltammetry. The GO-HATU material was more thermally stable than other graphitic material, with at 10% weight loss at 300°C, this thermal stability is related to a more difficult intramolecular physisorbed water removal process than the other d-GO materials. GO-CC and GO-HATU materials presented 8.2 and 8.0 Å of interlayer spacing, which was associated with a good oxidation-doping process. Besides, these two materials showed modifications in the vibrations by FTIR technique, corresponding to epoxy and hydroxyl groups of the GO being more susceptible to react with the amino groups. Moreover, I D /I G ratio calculated by Raman Spectroscopy presents the following trend 0.70, 0.94, 0.97 and 1.04 for GO, GO-CC, GO-DCC and GO-HATU, respectively, this increase is related with a major disorder during the doping process. XPS analysis shows C-N and N=C bands for high resolution of C 1s and N 1s, respectively, for d-GO materials. This possibly suggests the formation of benzimidazoles during the oxidation-doping process, this generates a similar -non-lattice and -lattice oxygen amount for O 1s related to crosslinking between the functional groups of GO and DAB which improve the electronic mobility between the surface and the bulk of the final graphitic material. Finally, the obtained d-GO materials were investigated as a working electrode for electrochemical capacitors and all of them showed typical capacitive behaviour. applications, including conductive polymer composites [2] supercapacitors [3], molecular, electrochemical, or biochemical sensors [4], antigen biosensors [5], lithium storage materials [6], amongst others.GO's diverse physicochemical properties are due to the synthesis method and the degree of oxidation generating disorganization of the structure. The oxidation exhibits lamellar structure with randomly distributed unoxidized aromatic regions (sp 2 -carbon atoms), six-membered aliphatic regions (sp 3 -carbon atoms), GO's interlayer spacing is about two times larger at ∼0.7 nm than that of graphite [7]. The space between layers results in different hydration capacities with intermolecular attraction type Van der Waals forces. The interlayer spacing caused by the oxidation process generates ortho-quinone, ketone, para-quinone, carboxyl, hydroxyl and epoxy functional groups, which are capable of facilitating a broad range of synthetic transformations. Popular synthesis methods are Brodie, Staudenmaier, Staudenmaier-Hofmann-Hamdi and Hummer, this last method being one of th...

The deuterium‐induced 13C isotope shifts of 21 nitrogen‐containing benzoheterocyclic systems labelled at the NH position were measured in DMSO‐d6 . The compounds included bridged diphenylamines, benzolactams, 4‐quinolinone, acridinones, carbazoles and indoles. The variations of two‐bond isotope effects are discussed as a function of cross‐conjugation of the N—H(D) group and acidity of the NH proton. Copyright © 1999 John Wiley & Sons, Ltd.

Purpose This paper aims to evaluate the corrosion inhibition capacities of synthesized compounds 1-(2-pyridinyl)-2-(o, m-, p-hydroxyphenyl) benzimidazoles in API 5L X52 steel/HCl 1M corrosion system. Design/methodology/approach Electrochemical impedance spectroscopy technique was used. Findings The studies determined that under stagnant conditions, the durability and efficiency were maintained over 80 per cent for up to 500 h of immersion, while the residence time started to decrease after 150 h at the best inhibitor concentration (150 ppm). Practical implications This work may help to attenuate corrosion problems in the petroleum industry. Originality/value It is the first time that 1-(2-pyridiniy)-2-(o-, m-, p-hydroxyphenyl) benzimidazoles were evaluated as corrosion inhibitors.

A series of C-8 mono-and disubstituted isatylidenes were prepared in order to examine the influence of the substituent on the polarization of the ethylenic carbons C-3 C-8. Donor-acceptor C-8 substitution resulted in an inversion of the polarization of the ethylenic carbons, as evidenced by the 13 C NMR spectra, and because these compounds can exist in solution as equilibrium mixtures of the E-and Z-isomers. The dual donor-acceptor character of the heterocycle is controlled by the cross-conjugated C-3 C-8 double bond, in which the C-3 carbon atom has the possibility of conjugating with either the donor or the attracting portion of the heterocyclic system, consistent with contributions from isatylidene resonance forms which induce the C-8 carbon atom to be charged either positively or negatively, thus allowing an opposite sense of the push-pull effect.

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