Carbon Bond Research Articles

Long-term performance: strength and metal encapsulation in alkali-activated iron ore tailings.

Understanding the strength behavior and leaching characteristics of mining tailings stabilized with alkali-activated cements in the short, medium, and long term is crucial for the feasibility of material applications. In this context, this study assessed the stabilization/solidification of iron ore tailings (IOT) using alkali-activated binder (AAB) composed of sugarcane bagasse ash and eggshell lime at curing times of 7, 28, 60, 90, 180, and 365days. Additionally, leaching tests were conducted, along with the examination of possible changes in the chemical and mineralogical composition resulting from exposure to acidic environments. Tests included unconfined compression strength (UCS), leaching, X-ray diffraction, and Fourier-transform infrared spectroscopy for the IOT-AAB mixtures. The highest increase in UCS was observed between 7 and 60days, reaching 6.47MPa, with minimal variation thereafter. The AAB-bonded IOT exhibited no metal toxicity over time. Elements Ba, Mn, Pb, and Zn present in IOT and ash were encapsulated in the cemented matrix, with complete encapsulation of all metals observed from 90days of curing time. The mineralogy of the stabilized/solidified tailings showed no changes resulting from leaching tests. Characteristic bands associated with the presence of N-A-S-H gel were identified in both pre-leaching and post-leaching samples for all curing times analyzed. Exposure to acidic environments altered bands related to carbonate bonds formed in the IOT-AAB mixture.

Study on the thermodynamic mechanism of external magnetic field on gas explosion characteristics

To investigate the thermodynamic mechanism of the magnetic field on the explosion characteristics of gases, experiments were carried out to study the influence of the applied magnetic field of 300 mT on the explosion characteristics of 5.7 % C2H6, 6.5 % C2H4 and 7.7 % C2H2 by volume. CHEMKIN-PRO software was used to simulate the three kinds of gas explosion chain reaction process. The chemical bond strength, stability and bond energy of the three gases were calculated and analyzed by Materials Studio software to derive the strength of chemical bond stability of the three gas molecules in the explosion process. The results show that the magnetic field weakened the breaking rate of CC, CC, and CC, the maximum explosion pressures of C2H6, C2H4, and C2H2 were reduced by 12.14 %, 16.47 %, and 18.71 %. The three gases carbon–carbon bond strength was weaker than the strength of the carbon-hydrogen bond, carbon-hydrogen bond was not easy to break, which in turn reduced the rate of generation of ·H in the chain initiation stage of the cleavage reaction, thus presenting a significant inhibitory effect of the magnetic field on C2H6, C2H4, and C2H2 explosions. The COOP of CC is 0.377 Ha, and the bond energy is 839 KJ/mol, which was greater than CC and CC, so the number of free radicals generated in the C2H2 cleavage reaction was lower, leading to a slower chain reaction rate which led to a stronger inhibitory effect of the magnetic field on C2H2 explosions than that on C2H6 and C2H4.

A combined experimental and theoretical study on the mechanism of catalytic oxidation of lignite to carboxylic acids by iron

The oxygen-oxidation of lignite to carboxylic acids (CAs) using environmentally friendly iron catalyst represents an efficient and clean technology for lignite utilization. However, the mechanism remains unclear due to the difficulty in observing the cleavage of chemical bonds and the challenge in capturing transient intermediates and radicals. In this work, the microscopic reaction mechanism of iron-catalytic oxidation of lignite was investigated by combining experimental and theoretical methods. Catalytic oxidation experiments revealed that water-soluble intermediates generated by solid-state lignite decomposition underwent a continuous carbon–carbon bond cleavage oxidation (including oxidative cleavage of aliphatic moieties and oxidative ring-opening of aromatic moieties) to form CAs with aldehyde moieties as the direct precursor. Based on molecular dynamics simulations and density functional theory, a reaction network from lignite to CAs was proposed. The iron catalyst was present in the form of iron-aqua complexes in the liquid phase and iron-phenyl complexes in the solid phase. These iron-aqua/iron-phenyl complexes could reduce the energies of oxidation reactions, promoting the cleavage of bridge bonds, the formation of o-quinones and the oxidation of aromatic moieties, thus accelerating elementary reactions for the formation of CAs. These findings provide a theoretical support for the oxidation of lignite and an in-depth insight into iron-catalytic mechanism.

Cobalt Carbon Bonding during Carbon Hydrogasification Revealed by 59Co Internal Field NMR

Cobalt Carbon Bonding during Carbon Hydrogasification Revealed by ⁵⁹Co Internal Field NMR

Construction of graphdiyne-based photocatalysts with strong built-in electric field by loading bimetallic oxides to promote the photocatalytic hydrogen evolution activity

The novel carbon material graphdiyne (GDY) is a two-dimensional planar structure material formed by the hybridization of sp and sp2, which has abundant carbon–carbon bonds and stable semiconductor properties. In this work, CoTiO3 was coupled with a carbon material GDY to successfully construct an S-scheme GDY/CoTiO3 heterojunction. This form of heterojunction can effectively promote the separation of charge carriers and shorten the electron transfer pathn. The loading of CoTiO3 effectively enhances the charge transfer rate of GDY and increases the number of photo-generated electrons involved in the hydrogen production reaction, thereby promoting hydrogen generation. The tests results demonstrate that GDY/CoTiO3-25 achieves a hydrogen production of 123.95 μmol under visible light irradiation, which is 13 times higher compared to GDY. This work provides insights into improving the photocatalytic performance of the novel carbon material GDY.

Long carbon–carbon bonds and beyond

Advances in synthetic organic chemistry have facilitated the preparation and exploration of compounds exhibiting unusual bonding states. This review delves into carbon–carbon single bonds that are exceeding typical length of bonds, elucidating recent advances in understanding their bonding nature, properties, and chemical reactivity. Additionally, we examine factors contributing to the occurrence of such elongated bonds and their effects on other bonding parameters. Furthermore, we shift our focus toward the π-dimers of radical species, surpassing the limit of two-center two-electron (2c/2e) bonds, discussing their formation mechanisms, stability, and inherent properties. A key feature in the electronic structure of π-dimers is the bonding interaction of two unpaired electrons spanning multiple atoms, that is, multicenter two-electron (mc/2e) bonding. This review sheds light on the significant role played by extended carbon–carbon bonds (2c/2e bonds) and radical π-dimers (mc/2e bonding) in organic chemistry, providing valuable insight for future research on new functional materials.

Enhanced tribological behavior and corrosion resistance in AlSiC-based coatings through varied carbon content

A series of AlSiC-based nanocomposite coatings with varying carbon concentrations were fabricated by filtered cathodic vacuum arc (FCVA) technology. These coatings featured an amorphous matrix with embedded Al4Si3C6 nanocrystals. With the increase in carbon content, the proportion of amorphous structure within the structure grew, which was accompanied by a rise in sp3 hybridized carbon bonds. This compositional change led to a significant enhancement in hardness and toughness. Notably, the AlSiC coating deposited at a flow rate of 50 sccm displayed exceptional mechanical properties, including a high hardness of approximately 23.2 GPa, toughness indices of H/E = 0.096 and H3/E2 = 0.216 GPa, a low friction coefficient around 0.18, a wear rate as low as ∼1.09 × 10−5 mm3 N−1 m−1, and a corrosion current density of approximately 1.08 × 10−9 A/cm2. The coating's superior tribological characteristics and corrosion resistance can be attributed to two main factors. The enhanced hardness and toughness indices (H/E and H3/E2) contributed to its improved deformability, which is essential for wear resistance. Secondly, the presence of a graphite layer formed during friction provided self-lubrication, further reducing wear. Additionally, the chemical inertness of both the amorphous SiC and the amorphous carbon phases within the nanocomposite structure significantly bolstered the coating's resistance to corrosion. The AlSiC nanocomposite coatings deposited by FCVA exhibit outstanding mechanical properties, tribological performance, and corrosion resistance, making them highly suitable for applications in environments where wear and corrosion are significant concerns.

Paddlanes revisited: Which are the smallest possible?

AbstractPaddlanes are tricyclic molecules with four bridging chains that share the same two bridgehead carbon atoms. The smallest known paddlane containing only carbon atoms in the main framework has a total of 18 atoms. We utilized computational chemistry (MP2/cc‐pVTZ) to locate the smallest possible all‐carbon paddlanes that meet the criterion suggested by Hoffmann, Schleyer, and Schaefer as being “fleeting,” meaning frequency calculations suggest the structures are energy minima on their respective potential energy surfaces (PES). Our results suggest that paddlane compounds with a total of 10 or fewer atoms can be considered to be non‐viable either because they are not energy minima on the PES or due to strain in the system that manifests as especially long carbon–carbon bonds. Some paddlanes with a total of 11 carbon atoms proved to be energy minima but still exhibited longer carbon–carbon bonds than normal. Finally, several paddlanes with a total of 12 carbons appear to be the least strained since carbon–carbon bond lengths remain reasonable.

Investigation on the steam gasification mechanism of different chars using isotopic tracing method

Gasification can provide syn-gas for consequent chemical production from carbon resources. The control of CO2 emission produced from gasification calls for the lower temperature and the more biomass char for the feed compared with traditional gasification, and the mechanism for steam gasification of different chars is more important. The gasification behaviors of four biomass chars and four coal chars are studied. The mechanism is probed using H216O/H218O period step tracing method coupled with various solid-state analyses on char structures. The increment of intermediates with increasing conversion demonstrate other slow step exists during gasification, and the solid state spectra of chars after and before gasification demonstrates that the condensation of poly-aromatic clusters in chars occurs accompanied with gasification. The addition reactions of radicals generated from gasifying agents and unsaturated carbon bonds C = C in chars is the slower step during gasification and enhancing the addition of radicals to unsaturated C = C bonds may be helpful for the higher gasification rate.

Large-deformation elastic hardening of a structured graphene kirigami nano-spring with re-entrant honeycombs

The programmable nature of graphene kirigami enables it highly applicable in the development of stretchable nanodevices. In this study, we employed molecular dynamics simulations to investigate the large deformation behavior of a structured graphene kirigami nano-spring (GKNS) with re-entrant honeycombs. During a uniaxial test, the elastic deformation can be categorized into two stages based on the applied load level. Stage I exhibits a maximal strain (εYstart) exceeding 50 % under low loading conditions, while stage II demonstrates a strain (εYend) surpassing 70 % at a high hardening rate. Both εYstart and εYend are greater than those observed in GKNS with transversal periodic boundary conditions. Furthermore, increasing the length or decreasing the width of bars within GKNS with cells of identical shape leads to an increase in both εYstart and εYend values. Ambient temperature has minimal impact on εYstart and εYend however, higher temperatures result in lower hardening rates due to weakened carbon–carbon bonds within GKNS structures. Additionally, variations in cell/void arrangement within structured GKNS affect both εYstart and εYend values, whereas widening the GKNS structure leads to reduced hardening rates. The findings presented herein provide valuable insights for designing nanodevices that necessitate significant deformations.

Visible light-driven organocatalyzed radical ring-opening polymerization of Bicyclo[1.1.0]butanes

Radical ring-opening polymerization (rROP) offers an essentially practical strategy to introduce a broad scope of functional groups in the polymer backbone. While suitable cyclic monomers mostly possess a vinyl group to facilitate the radical addition step, we herein present an efficient rROP of highly strained bicyclo[1.1.0]butane (BCB)-derived monomers through radical addition to bridge σ-carbon–carbon bond by photoinduced electron/energy transfer reversible addition−fragmentation chain transfer (PET-RAFT) polymerization technique, producing poly(BCBs) with relatively predictable molecular wight and low to moderate dispersity. Spatiotemporal control over the polymer chain-growth was achieved and high chain-end fidelity was imparted to access intriguing random and block copolymers with complex structures.

Enhancing optical biosensing: Comparing two physical treatments for GPTES chemical functionalization of Cyclo-Olefin Copolymer foil

Cyclo-olefin-copolymer (COC) transparent films are currently the best choice for micro-fluidic bio-sensors for point-of-care diagnostic applications using optical signal detection. However, while the optical and mechanical properties of this polymer are extremely good, the adhesion of the bio-probes on this surface is not optimal, due to its chemical structure, that presents only saturated carbon bonds. The deposition of organo-silane molecules on the COC surface is one of the most effective ways to overcome this problem. But, for the surface functionalization, a surface physical treatment is necessary before the chemical modification of the COC surface. In this paper a comparison of the effectiveness of two different physical treatments, oxygen plasma and UV-ozone, is reported. In particular, the exposure time of the UV-Ozone treatment has been selected to avoid the problem of auto-fluorescence of the modified COC surface, that was observed also for relatively short UV exposure (around 10 min). An investigation of the reactive radicals created on the surface after the physical treatments and the following chemical modification with the organo-silane molecule (GPTES) has been performed using X-ray photoemission spectroscopy. The surface energy and morphology of the films have been also measured by contact angle and optical profilometry. Finally, the bio-probes adhesion performances of the COC surfaces obtained with the two physical treatments and the chemical modification were tested in a fluorescence-based assay, using an organic light emission diode to excite the fluorescence. We observed that the UV-ozone treatment allows to obtain a siloxane network with some reactive epoxy radicals on the COC surface, however, their quantity and distribution are less important and homogeneous than in the oxygen plasma treated surfaces.

Anion- and water-facilitated oxidative carbon–carbon bond cleavage and diketonate carboxylation in Cu(II) chlorodiketonate complexes

The O2-dependent carbon–carbon (CC) bond cleavage reactions of the mononuclear Cu(II) chlorodiketonate complexes [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 (1-ClO4) and [(bpy)Cu(PhC(O)CClC(O)Ph)(ClO4)] (3-ClO4) have been further examined in terms of their anion and water dependence. The bpy-ligated Cu(II) chlorodiketonate complex 3-ClO4 is inherently more reactive with O2 than the 6-Ph2TPA-ligated analog 1-ClO4. Added chloride is needed to facilitate O2 reactivity for 1-ClO4 but not for 3-ClO4 at 25(1) °C. Evaluation of kobs for the reaction of 1-ClO4 with O2 under pseudo first-order conditions as a function of the amount of added chloride ion produced saturation type behavior. The bpy-ligated 3-ClO4 exhibits different behavior, with rate enhancement resulting from both the addition of chloride ion and water. Computational studies indicate that the presence of water lowers the barrier for O2 activation for 3-ClO4 by ∼12 kcal/mol whereas changing the anion from perchlorate to chloride has a smaller effect (lowering of the barrier by ∼3 kcal/mol). Notably, the effect of water for 3-ClO4 is of similar magnitude to the barrier-lowering chloride effect found in the O2 activation pathway for 1-ClO4. Thus, both systems involve lower energy O2 activation pathways available, albeit resulting from different ligand effects. Probing the effect of added benzoate anion, it was found that the chloro substituent in the diketonate moiety of 1-ClO4 and 3-ClO4 will undergo displacement upon treatment of each complex with tetrabutyl ammonium benzoate to give Cu(II) benzoyloxydiketonate complexes (4 and 5). Complexes 4 and 5 exhibit slow O2-dependent CC cleavage in the presence of added chloride ion. These results are discussed in the context of the chemistry identified for various divalent metal chlorodiketonate complexes, which have relevance to catalytic systems and metalloenzymes that mediate O2-dependent CC cleavage within diketonate substrates.

A cobalt templated outer sphere hydrogen bond donor catalyst derived from 2-guanidinobenzimidazole: Synthesis, applications in carbon–carbon bond forming reactions, structure

A lipophilic tricationic cobalt tris(chelate) complex of 2-guanidinobenzimidazole (GBI), [Co(GBI)3]3+ 3BArf– (23+ 3BArf–; BArf = B(3,5-C6H3(CF3)2)4), is prepared from the corresponding hydrophilic trichloride salt and Na+ BArf– or Ag+ BArf– under aqueous/organic biphasic conditions. This racemic chiral complex, which is obtained as a mer isomer and a tetradecahydrate as assayed by NMR and TGA, is an excellent catalyst for additions of dimethyl malonate and indole to trans-ß-nitrostyrenes (10 mol%), and cycloadditions of CO2 to epoxides (1 mol%; solvent-free). Average yields (84 %, 91 %, 81 %) and rates are slightly greater than those obtained with a monocationic ruthenium GBI complex [(η5-C5H5)Ru(CO)(GBI)]+ BArf– prepared earlier. Attempted crystallization of 23+ 3Cl– gives a tetramethanol solvate of a salt derived from loss of two molecules of HCl. This can be represented as [Co(GBI)(GBI–H)2]+ Cl−, and bond lengths and hydrogen bonding motifs are carefully analyzed, especially in the context of dominant chelate resonance forms.

Tailoring crystalline orientation of electrodeposited cobalt by alkynol additives

Additives play a pivotal role in achieving high-quality electrodeposited cobalt films for diverse applications in microelectronics. In this work, 1,4-butynediol (BYD) bearing function groups of CC and -OH, 1,4-butenediol (BED) featuring C = C and -OH, and glycol (EG) with only -OH were studied to reveal the potential underlying mechanism of unsaturated carbon bonds on cobalt electrodeposition. It is found that BYD inhibits both the cobalt deposition and the formation of adsorbed hydrogen, forming compact cobalt film. Furthermore, the surface and cross-section morphology, grain structure, and resistivity of electrodeposited cobalt are characterized to investigate the effects of alkynol additives. It was observed that BYD induces a change in surface morphology from a mixture of elongated ridges and granular shapes to a flattened granular structure. The texture of the electrodeposited cobalt film transformed from hcp(100) and hcp(101) to hcp(002) with the addition of BYD due to the selective absorption of BYD on specific cobalt orientation. This study not only regulates the grains orientations and properties of electrodeposited cobalt, but also enhances the comprehension of the effect and mechanism of unsaturated carbon bonds on cobalt electrodeposition. These findings provide a theoretical foundation for the selection of additives and their practical applications.

Functional group tolerant hydrogen borrowing C-alkylation

Hydrogen borrowing is an attractive and sustainable strategy for carbon–carbon bond formation that enables alcohols to be used as alkylating reagents in place of alkyl halides. However, despite intensive efforts, limited functional group tolerance is observed in this methodology, which we hypothesize is due to the high temperatures and harsh basic conditions often employed. Here we demonstrate that room temperature and functional group tolerant hydrogen borrowing can be achieved with a simple iridium catalyst in the presence of substoichiometric base without an excess of reagents. Achieving high yields necessitates the application of anaerobic conditions to counteract the oxygen sensitivity of the catalytic iridium hydride intermediate, which otherwise leads to catalyst degradation. Substrates containing heteroatoms capable of complexing the catalyst exhibit limited room temperature reactivity, but the application of moderately higher temperatures enables extension to a broad range of medicinally relevant nitrogen rich heterocycles. These newly developed conditions allow alcohols possessing functional groups that were previously incompatible with hydrogen borrowing reactions to be employed.

Review of TiO2 as Desulfurization Catalyst for Petroleum

In the relentless pursuit of sustainable energy solutions, the petroleum industry faces the imperative challenge of mitigating sulfur emissions. This comprehensive review scrutinizes Titanium Dioxide (TiO2) as an extraordinary catalyst, pushing the boundaries of desulfurization performance in petroleum refining. The abstract begins by underscoring the urgent need for advanced desulfurization technologies, driven by stringent environmental mandates and escalating global energy demands. The spotlight then shifts to the unparalleled physicochemical attributes of TiO2, showcasing its inherent advantages such as exceptional surface area, stability, and photocatalytic process. A profound exploration of TiO2’s catalytic mechanisms follows, unraveling its capacity to disintegrate stubborn sulfur–carbon bonds, thereby elevating desulfurization efficiency to unprecedented levels. This review meticulously dissects diverse forms of TiO2, ranging from nanoparticles to mesoporous structures, and provides a critical analysis of their respective strengths and limitations in catalyzing sulfur removal. Delving into operational nuances, this review examines the impact of temperature, pressure, and catalyst loading on TiO2 performance, offering crucial insights for optimizing desulfurization processes. The narrative then unfolds to explore cutting-edge developments in TiO2-based catalysts, encompassing ingenious modifications, composites, and hybrid materials designed to augment catalytic activity and selectivity. Anticipating the road ahead, this review contemplates the challenges and prospects of deploying TiO2 on an industrial scale, pointing toward avenues for future research and development. This abstract encapsulates a wealth of knowledge, serving as an indispensable resource for researchers, engineers, and policymakers navigating the dynamic landscape of sustainable petroleum refining. TiO2 emerges as a transformative force, propelling the industry toward cleaner, greener, and more efficient energy production.

The tension-activated carbon–carbon bond

The tension-activated carbon–carbon bond

Cross-Double Deoxygenative Carbon–Carbon Bond Formation between Benzyl Benzoates and Allylic Alcohols

Cross-Double Deoxygenative Carbon–Carbon Bond Formation between Benzyl Benzoates and Allylic Alcohols

Vanadium (IV)oxo catalyzed One-Pot transformation of cinnamate to aromatic ester and its mechanistic aspects

Metal-catalyzed oxidative cleavage of unsaturated carbon–carbon bond is among the utmost valuable chemical transformations in synthetic organic chemistry. However, the direct transformation of cinnamate to benzoate remains an unsolved task in the series. Herein, we have developed an unprecedented one-pot strategy for the direct transformation of cinnamate esters to aromatic ester using V-catalyst [(L2)VIVO](ClO4) and green oxidant H2O2 in alcohol-reflux condition. The reaction on cinnamate proceeded via CC bond breaking to generate aldehyde intermediate, followed by oxidative esterification to yield two carbon less aromatic esters in 52–95% yields. Further, experimental and DFT studies confirmed the mechanism and in-situ aldehyde formation which consequently supported to the developed protocol.