Ni2+ cation and imidazole as corrosion inhibitors for carbon steel in sulfuric acid solutions

Abstract  

The effect of Ni²⁺ cation, imidazole, and mixtures of them on the corrosion behavior of carbon steel in 0.5 M H₂SO₄ solution was studied by using galvanostatic polarization, potentiodynamic anodic polarization, and weight-loss techniques. Ni²⁺ cation, imidazole, and mixtures of them provide a good protection to carbon steel against pitting corrosion in chloride-containing solutions. The inhibiting solutions were analyzed by using UV–Vis spectrophotometry. The inhibition was explained on the basis of formation of a complex between the two components. The inhibition mechanism was discussed in terms of the results derived from corrosion and UV–Vis spectrophotometric measurements as well as conductometric investigations.     

Identification of the adsorption sites of molecular oxygen on Si(111) using XPS

Most of the oxygen adsorb dissociatively on Si, however there is also a significant amount of metastable molecular oxygen chemisorbed on Si. The adsorption site/configuration of these molecular oxygen species is still a controversial subject. New XPS results for oxygen adsorption on Si(111) 7×7 (150K) are presented. They reveal four distinct oxygen components; one of the metastable components has never been reported before. We tentatively identify them as: i) stable oxide (Si-O-Si bridges)(˜532 eV), ii) diffusing oxygen atom (˜533 eV) in silicon oxide and iii) metastable molecular oxygen species (˜527.6 eV and ˜530.6 eV). The latter have been attributed to peroxy radical which is defined as a diatomic oxygen bonded to a single Si adatom. Our results allow us to distinguish the two main configurations of peroxy radical: paul-para and grif. Both of them possess a lifetime of ˜ 180 min.     

An efficient synthesis of pyrrolo[3′,2′:4,5]thiopyrano[3,2-b]pyridin-2-one: a new ring system of pharmaceutical interest

A series of pyrrolo[3′,2′:4,5]thiopyrano[3,2-b]pyridin-2-ones 4 was prepared in good yields by reacting enaminoketones with cyanomethylene active compounds such as phenylsulfonylacetonitrile, benzoylacetonitrile, and malononitrile. Derivatives of the title ring system were tested by the National Cancer Institute of Bethesda against a panel of about 60 human tumor cell lines, and one of them showed inhibitory activity against all cancer cell lines reaching on 48% of them GI₅₀ values at submicromolar level and on the majority of the remaining ones in the low micromolar concentration.     

A new steroidal saponin from Dioscorea zingiberensis Wright

Two compounds were obtained from the rhizome of Dioscorea zingiberensis Wright. One of them was elucidated as dioscin, the other one was a new compound and characterized as Spirost-5-en-3-yl beta-D-glucopyranosyl (1 --> 3)-beta-D-glucopyranosyl (1 --> 4)-[alpha-L-rhamnopyranosyl (1 --> 2)]-beta-D-glucopyranoside, structure was determined on the basis 2D NMR spectroscopic technique and the result of acid hydrolysis.     

Investigation of the cardiotoxic peptides of the venom of the cobraNaja oxiana

Six populations of basic polypeptides have been found in the venom of the Central Asian cobraNaja oxiana Eichwald, and four of them — V″c-1, V″c-2, V″c-5, and V″c-6 — have been obtained in the electrophoretically homogeneous state. On a perfused frog heart preparation, all the basic polypeptides proved to be cardiotoxic. However, only some of them (V′c-2, V″c-3, and V″c-4) were characterized by arrhythmic activity as well as by the negative ino- and chronotropic effects, common for all of them. An enhancement of the specific cardiotoxic effect of each of the polypeptides by pure phospholipase A-2 has been shown.     

Die Produkte der Thermolyse von N-(1-Pyridinio)-2-nitroaniliden sind keine Triaziridine,sondern 1, 2-Bis[(2′-nitrophenyl)-azoxyl]-benzole

The products of the thermolysis of N-(1-pyridinio)-2-nitroanilides ( 1 ) had previously been interpreted as tris (2-nitrophenyl)-triaziridines ( 3 ). The present work shows them to be actually 1, 2-bis[(Z)-(2′-nitrophenyl)-ONN-azoxy]benzenes ( 5 ). The revised structural assignment is based on the chemical and the spectroscopic (especially ¹H-NMR.) properties of 5 and on the results of a X-ray structural analysis.     

Cyclic hydroxamic acids derived from quinazoliue

The action of various acylating agents on 2-aminobenzohydroxamic acid afforded 3-hydroxy-4(3H)quinazolinones (hydroxamic acids) as well as several ethers and esters from them were prepared and their spectroscopic properties analyzed. Secondary amines, as well as one equivalent of alkali, on 2-halomethyl-3-hydroxy-4(3H)quinazolinone lead to the formation of a dimer(XI). In this respect the behaviour of secondary amines is different from that of primary amines. Some new 3-hydroxy-2-4(1H,3H)-quinazolidinediones are described.     

Selected β2-, β3- and β2,3-Amino Acid Heterocyclic Derivatives and Their Biological Perspective

Heterocyclic moieties, especially five and six-membered rings containing nitrogen, oxygen or sulfur atoms, are broadly distributed in nature. Among them, synthetic and natural alike are pharmacologically active compounds and have always been at the forefront of attention due to their pharmacological properties. Heterocycles can be divided into different groups based on the presence of characteristic structural motifs. The presence of β-amino acid and heterocyclic core in one compound is very interesting; additionally, it very often plays a vital role in their biological activity. Usually, such compounds are not considered to be chemicals containing a β-amino acid motif; however, considering them as this class of compounds may open new routes of their preparation and application as new drug precursors or even drugs. The possibility of their application as nonproteinogenic amino acid residues in peptide or peptide derivatives synthesis to prepare a new class of compounds is also promising. This review highlights the actual state of knowledge about β-amino acid moiety-containing heterocycles presenting antiviral, anti-inflammatory, antibacterial compounds, anaplastic lymphoma kinase (ALK) inhibitors, as well as agonist and antagonists of the receptors.     

Plasmonic Au-Metal Oxide Nanocomposites for High-Temperature and Harsh Environment Sensing Applications

Noble metal nanoparticles like Au have long been admired for their brilliant colour, significantly influenced by plasmon resonance. When embedded in metal oxides, they exhibit unique properties which make them an excellent choice for sensing in high-temperature and harsh environment atmospheres. In this review, the various morphologies of Au nanoparticles (AuNPs) used in combination with metal oxides for sensing gases at temperatures greater than 300 °C are discussed. Theoretical discussions on the plasmon resonance properties of AuNPs as well as computational techniques like finite difference time domain (FDTD), are often used for understanding and correlating their extinction spectra and are briefed initially. The sensing properties of AuNPs embedded on a metal oxide matrix (such as TiO₂, SiO₂, NiO etc) for quantifying multiple analytes are then elucidated. The effect of high temperature as well as gas environments including corrosive atmospheres on such nanocomposites, and the different approaches to comprehend them are presented. Finally, techniques and methods to improve on the challenges associated with the realization and integration such Au-metal oxide plasmonic nanostructures for applications such as combustion monitoring, fuel cells, and other applications are discussed.     

Stereochemistry of the initiation step in Ziegler-Natta catalysts containing dialkyl propane diethers: A tool for distinguishing the role of internal and external donors

The results of a study on a new generation of MgCl₂ supported Ziegler-Natta catalysts that contain dialkyl propane diethers as internal donors and produce highly stereospecific polypropene even without any external donor are presented. The results concerning three different catalysts containing 2,2-diisobutyl-1,3-dimethoxy propane (DIBDMP), 2,2-dicyclopentyl-1,3-dimethoxy propane (DCPDMP) and 2-ethyl,2-butyl-1,3-dimethoxy propane (EBDMP) as internal donors are compared. The same donors have also been studied by using them as external donors with a catalyst contaning diisobutyl phthalate as internal donor. The present results, along with previously obtained findings on traditional supported Ziegler-Natta catalysts, permit a general comprehension of the role of internal and external donors.     

One-step to get 5-azidomethyl-2′-deoxyuridine from 5-hydroxymethyl-2′-deoxyuridine and detection of it through click reaction

Nowadays a few ways to synthesize 5-azidomethyl-2′-deoxyuridine from 5-hydroxymethyl-2′-deoxyuridine have been reported. But none of them was one-step. And many of them need to protect the hydroxyl group on the pentose ring. The detection of 5-hydroxymethyl-2′-deoxyuridine is also very important in many biological processes. However few fluorescence detection strategies have been tried to do this. Herein, we reported a one-step protocol to synthesize 5-azidomethyl-2′-deoxyuridine, which was then used for detecting 5-hydroxymethyl-2′-deoxyuridine through a click reaction.     

Low temperature dielectric relaxation spectroscopy

It has been found during the last 2$\text{1}\text{2}$ years that dielectric relaxations associated with many organic compounds could be observed by dissolving or dispersing them in hydrocarbon solvents or matrices and cooling them to 4.2 K. Such relaxations were nearly always attributable to conformational changes of independent solute or dopant molecules and could be used as a means of spectroscopic investigation. Two ways of using such data are outlined and the advantages and limitations are discussed using ROH, RSH and R₁R₂NH compounds as examples.     

Selective electroreduction of carbon dioxide to formic acid on electrodeposited SnO<Subscript>2</Subscript>@N-doped porous carbon catalysts

Electrocatalytic reduction of CO₂ is a promising route for energy storage and utilization. Herein we synthesized SnO₂ nanosheets and supported them on N-doped porous carbon (N-PC) by electrodeposition for the first time. The SnO₂ and N-PC in the SnO₂@N-PC composites had exellent synergistic effect for electrocatalytic reduction of CO₂ to HCOOH. The Faradaic efficiency of HCOOH could be as high as 94.1% with a current density of 28.4 mA cm^?2 in ionic liquid-MeCN system. The reaction mechanism was proposed on the basis of some control experiments. This work opens a new way to prepare composite electrode for electrochemical reduction of CO₂.     

Geminal interaction and “anomeric effect”

Quantum-chemical calculations by the methods of RHF/6-31G(d) and MP2/6-31+G(d) show equal ratio of the lengths of axial and equatorial bonds and electron density on the atoms forming them in cyclohexane and its mono derivatives and in six-membered heterocyclic molecules as well. This feature is due to the interaction of atoms in the chair form of these molecules regardless of the presence in them of a heteroatom. Introducing heteroatom to a cyclohexane ring leads only to increase in the difference between axial and equatorial bonds. This equation excludes the possibility to ascribe the elongation of axial bonds and increase in the electron density on atoms forming them in the heterocyclic molecules to the p,σ*-conjugation of the lone electron pair of the ring heteroatom with the antibonding orbital of the axial bond. Features of molecular geometry defined by the mutual influence of atoms in them, including inductive and non-inductive interaction of geminal atoms in triatomic groups Y-Z-M, result in energetic preference of gauche conformations of these molecules and “anomeric effect” in them.     

Sulfur Oxides as Ligands in Coordination Compounds

Donor molecules undergo dramatic changes in their chemical properties on coordination to a transition-metal atom. Highly reactive species can be trapped and studied as ligands. Conversely, stable compounds can be activated to undergo novel reactions. Sulfur dioxide complexes have generally been studied from a structural viewpoint, their reactivity having been somewhat neglected. The unstable sulfur oxides SO, S₂O, and S₂O₂ are still often regarded as laboratory curiosities. Their successful stabilization in transition-metal complexes has now made them accessible to detailed study, in the course of which many relationships to the chemistry of SO₂ complexes have become apparent.     

Study of Different Catalysts and Initiators in Bulk Copolymerization of d,l-Lactide and Glycolide

Poly(d,l-lactide-co-glycolide), PLGA, is a biodegradable polyester with many medical applications. In this article, several catalysts are studied as potential substitutes of the conventional catalyst, tin (II) 2-ethylhexanoate (known as tin octoate, SnOct₂). Namely, different metal carboxylates have been examined, in order to study the influence of the metal counterion. Among them, most promising results have been obtained when using zinc (II) 2-ethylhexanoate (ZnOct₂) followed by potassium (I) 2-ethylhexanoate. Furthermore, in the case of ZnOct₂, the use of alcohols as initiators was examined in order to improve reaction rate and to study their effect on molecular weight distribution, polymer microstructure, and side reactions, such as transesterification reaction.     

2D Nb4N5 Nanosheets Synthesized by a Template Method

Niobium nitrides possess superconductivity and stable chemical stability, which render them desirable candidates for energy storage. Therefore, they deserve exploration for potential energy storage applications. Here we report on the synthesis of 2D Nb₄N₅ nanosheets by ammonization of NbS₂ nanosheets as templates at 700 °C. The obtained 2D Nb₄N₅ nanosheets retain their hexagon shape and display a porous structure with a pore size of 3.716 nm. These 2D Nb₄N₅ nanosheets exhibit capacitor behavior as electrode materials for energy storage. This study opens a new avenue in synthesizing 2D materials based on 2D templates.     

Tin(II)-Based Metal–Organic Frameworks Enabling Efficient,Selective Reduction of CO2 to Formate under Visible Light

Certain metal complexes are known as high-performance CO₂ reduction photocatalysts driven by visible light. However, most of them rely on rare, precious metals as principal components, and integrating the functions of light absorption and catalysis into a single molecular unit based on abundant metals remains a challenge. Metal-organic frameworks (MOFs), which can be regarded as intermediate compounds between molecules and inorganic solids, are potential platforms for the construction of a simple photocatalytic system composed only of Earth-abundant nontoxic elements. In this work, we report that a tin-based MOF enables the conversion of CO₂ into formic acid with a record high apparent quantum yield (9.8 % at 400 nm) and >99 % selectivity without the need for any additional photosensitizer or catalyst. This work highlights a new MOF with strong potential for photocatalytic CO₂ reduction driven by solar energy.     

Phenanthroline–dipyrromethene conjugates: synthesis,characterization, and spectroscopic investigations

Mono- and tri-topic ligands, based on dipyrromethenes and the 1,10-phenanthroline nucleus, as well as BF₂ complexes derived thereof are described. While BODIPY 12 has been X-ray crystallographically characterized, the structural features of the free ligands 9 and 10 may render them useful as precursors for the elaboration of novel supramolecular architectures.     

SYNTHESIS AND CONFIGURATIONAL STUDIES OF ARYL CYCLOPROPYL SULFONES

Abstract

The cycloaddition of arylthiocarbenes to styrene gave stereospecifically cis?1-(arylthio)-2-phenylcyclopropanes, which were subsequently oxidized to the corresponding sulfones. The cyclopropanation of α,β-unsaturated sulfones with dimethylsulfonium methylide yielded stereoselectively trans?1-(arylsulfonyl)-2-arylcyclopropanes. The configurational assignments of these compounds have been arrived at on the basis of IR and PMR spectral data. Chemical shifts for ring protons and other substituents reveal that all the substituents tend to cause protons cis to them to appear at higher fields than those trans to them. This has been used as a criterion to distinguish between cis and trans aryl cyclopropyl sulfones.