Sustainable utilisation of calcium-rich industrial wastes in soil stabilisation: Potential use of calcium carbide residue.

Calcium carbide residue (CCR), a by-product of the acetylene industry, is generated at a rate of 136 million tonnes per year, posing significant environmental risks. This review examines the potential utilisation of CCR in soil stabilisation, focusing on its stabilisation mechanism, performance in improving mechanical properties, environmental safety, and sustainability. The aim is to identify future research directions for CCR-based stabilisation to promote its broader application, and to provide references for managing similar Ca-rich wastes. CCR-based materials demonstrate promising benefits in enhancing various soil properties, such as uniaxial strength, swelling properties, triaxial shear behaviour, compressibility, and dynamic responses, while also reducing the mobility of contaminants. Compared to conventional stabilisers, CCR-based materials exhibit comparable performance in soil improvement, environmental impact and safety, and economic feasibility. However, further research is required to delve deeper into stabilisation mechanisms, mechanical properties, and stability of contaminants for the soil treated with CCR-based materials under diverse conditions.

Smoke-water obtained via different biotics: a cost-effective and safer approach to biochemically sound banana ripening with prolonged shelf-life.

This study was conducted to investigate the efficacy of smoke-water obtained from biotics, for example coconut shells, rice husk, and pine cones on banana ripening, and compared with calcium carbide. Bio-chemical composition and remarkable bactericidal effect towards ATCC cultures of Escherichia coli, Staphylococcus aureus, and Bacillus cereus discovered the biological safety of the smoke-water in all collected smoke-water samples. Further, inductively coupled plasma mass spectrometry (ICP-MS) was carried out to investigate heavy metals; however, no traces were found in all collected samples. Consequently, it is proposed that heavy metal-free smoke-water obtained from various biotics series might be employed as ultrasafe fruit ripening as compared to calcium carbide (CaC2) that was found with heavy metal traces.

Towards Sustainable Carbon Return from Waste to Industry via C2-Type Molecular Unit.

A general possibility of a sustainable cycle for carbon return to high-value-added products is discussed by turning wastes into acetylene. Pyrolyzed solid municipal wastes, pyrolyzed used cationic exchangers, and other waste carbon sources were studied in view of the design of a sustainable cycle for producing calcium carbide and acetylene. The yields of calcium carbide from carbon wastes were as high as those from industrial fossil raw materials (coke, charcoal, etc.). Conversion of carbon-containing wastes to calcium carbide provides an excellent opportunity to make acetylene, which is directly compatible with modern industry. Overall, the process returns carbon-containing wastes back to sustainable cycles to produce high-value-added products involving only C2-type molecules (calcium carbide and acetylene). Calcium carbide may be stored and transported, and on-demand acetylene generation is easy to realize. Upon incorporation into the waste processing route, calcium carbide may be an efficient carbon reservoir for quick industrial uptake.

Selective Monoethynylation of 2-Oxoacetamides Using Calcium Carbide as a Concise Solid Alkyne Source.

An efficient selective monoethynylation of 2-oxoacetamides using calcium carbide as a concise solid alkyne source is described. A series of multifunctional compounds, 2-hydroxybut-3-ynamides, are synthesized by this strategy. The salient features of this protocol are the use of inexpensive and easy-to-handle solid alkyne source as a surrogate of inflammable and explosive gaseous acetylene, transition-metal-free and mild condition, wide scope of substrates, high selectivity, high yield, and simple work-up procedure.

Dinuclear gold(I) Complexes with Bidentate NHC Ligands as Precursors for Alkynyl Complexes via Mechanochemistry.

The use of alkynyl gold(I) complexes covers different research fields, such as bioinorganic chemistry, catalysis, and material science, considering the luminescent properties of the complexes. Regarding this last application, we report here the synthesis of three novel dinuclear gold(I) complexes of the general formula [(diNHC)(Au-C≡CPh)2]: two Au-C≡CPh units are connected by a bridging di(N-heterocyclic carbene) ligand, which should favor the establishment of semi-supported aurophilic interactions. The complexes can be easily synthesized through mechanochemistry upon reacting the pristine dibromido complexes [(diNHC)(AuBr)2] with phenylacetylene and KOH. Interestingly, we were also able to isolate the monosubstituted complex [(diNHC)(Au-C≡CPh)(AuBr)]. The gold(I) species were fully characterized by multinuclear NMR spectroscopy and mass spectrometry. The emission properties were also evaluated, and the salient data are comparable to those of analogous compounds reported in the literature.

Enantioseparation on helical poly(diphenylacetylene)s bearing optically-active pendants: Effects of differences in higher-order structures of kinetically-trapped and thermodynamically-stable states on chiral recognition ability.

An optically-active poly(diphenylacetylene) (PDPA) bearing carboxy pendant groups with left-handed helicity memory (M-h-poly-1), synthesized using the noncovalent helicity-induction-and-memory strategy, was converted into a PDPA bearing optically-active pendant groups through an amide bonding (M-hKT-poly-2S), while maintaining the left-handed helicity memory, by reaction with (S)-1-phenylethylamine ((S)-2) using a condensing reagent at room temperature. Its chiral recognition ability was investigated as a chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). M-hKT-poly-2S exhibited significantly different chiral recognition ability towards racemates compared to the previously reported corresponding helical PDPA bearing the same optically-active pendant groups (M-hTS-poly-2S) (prepared by the reaction of an optically-inactive PDPA bearing carboxy pendants with (S)-2, followed by thermal annealing, to induce a left-handed helical structure in the polymer main chain). Although the main chains of both M-hKT-poly-2S and M-hTS-poly-2S formed almost completely left-handed helical structures, their higher-order structures varied slightly, as confirmed by various spectroscopic methods (UV-Vis, circular dichroism (CD), IR, and vibrational CD). M-hKT-TS-poly-2S, the PDPA formed on the thermal annealing of M-hKT-poly-2S, exhibited the same higher-order structure and chiral discrimination ability as M-hTS-poly-2S. Therefore, slight differences in the higher-order structures of the kinetically-trapped metastable state (M-hKT-poly-2S) and the thermodynamically-stable state (M-hTS-poly-2S), due to differences in synthetic procedures, significantly impact their chiral recognition abilities as CSPs, even with identical primary structures and helix-sense of the polymer main chain.

Photostability and Dynamic Helical Behavior in Chiral Poly(phenylacetylene)s with a Preferred Screw-Sense.

Helical polymers such as poly(phenylacetylene)s (PPAs) are interesting materials due to the possibility of tuning their helical scaffold (sense and elongation) once they have been prepared and by the presence of external stimuli. The main limitation in the application of PPAs is their poor photostability. These polymers degrade under visible light exposure through a photochemical electrocyclization process. In this work, it was demonstrated, through a selected example, how the photochemical degradation in PPAs is directly related to their dynamic helical behavior. Thus, while PPAs with dynamic helical structures show poor photostability under UV/Vis light exposure, poly-(R)-1, bearing an enantiopure sulfoxide group as pendant group and designed to have a quasi-static helical behavior, shows a large photostability due to the restricted conformational composition at the polyene backbone, needed to orient the conjugated double bonds prior to the photochemical electrocyclization process and the subsequent degradation of the material.

Evaluation of the mechanical performance of concrete containing calcium carbide residue and nano silica using response surface methodology.

Calcium carbide residue (CCR) is generated from acetylene gas production, and it is highly alkaline and contains a very high amount of calcium. Nano silica (NS), on the other hand, is mostly used in combination with other pozzolanic materials in concrete to ignite the reactivity of the material and to improve the properties of the concrete. This study investigated the effect of CCR incorporated in concrete mixtures to partially replace cement content at 0 to 30% (interval of 7.5%). NS was used as an additive by weight of binder at levels 0 to 4% in increment of 1%. Thus, response surface methodology (RSM) was employed to investigate the effects of CCR and NS on the properties of the concrete, including compressive strength, flexural strength, splitting tensile strength, modulus of elasticity (MoE), and water absorption. The RSM was used for model development predicted concrete's properties and carried out mixture multi-objective optimization by maximizing strengths, MoE, and minimizing water absorption. The results showed that using up to 15% CCR improved the strengths, MoE, and water absorption of the concrete. Adding up to 3% NS further enhanced the strengths, MoE, and water absorption significantly. The developed models for predicting the properties of the concrete using RSM were highly efficient with high degree of correlation. The optimization solutions indicated that the best optimum or best mix combination based on maximum strengths and MoE with minimum water absorption was achieved by replacing 10.6% cement with CCR and adding 1.95% NS by the weight of cementitious materials.

Spontaneous, co-translational peptide macrocyclization using p-cyanoacetylene-phenylalanine.

Peptide macrocycles (PMCs) are increasingly popular for the development of inhibitors of protein-protein interactions (PPIs). Large libraries of PMCs are accessible using display technologies like mRNA display and phage display. These technologies require macrocyclization chemistries to be compatible with biological milieu, severely limiting the types of technologies available for cyclization. Here, we introduce the novel non-canonical amino acid (ncAA) p-cyanoacetylene-L-Phe (pCAF), which facilitates spontaneous, co-translational cyclization through Michael addition with cysteine under physiological conditions. This new, robust chemistry creates stable macrocycles of a wide variety of ring sizes including bicyclic structures.

Well-Controlled Living Polymerization of Phenylacetylenes in Water: Synthesis of Water-Soluble Stereoregular Telechelic Poly(phenylacetylene)s.

Well-controlled living polymerization of water-soluble phenylacetylene derivatives in water was achieved for the first time using a multicomponent catalytic system consisting of [Rh(nbd)Cl]2 , an aryl boronic acid, diphenylacetylene having carboxy groups, a tetraalkylammonium hydroxide, and a water-soluble triphenylphosphine. This catalytic system enables a direct synthesis of various water-soluble cis-stereoregular poly(phenylacetylene)s having a narrow molecular weight distribution, the molecular weight of which can be controlled by the initial feed ratio of the monomer to the catalyst. Moreover, the syntheses of water-soluble telechelic poly(phenylacetylene)s having various functional groups at both chain ends as well as a water-soluble block copolymer were achieved.

One-Pot Synthesis of 1,2-Disubstituted Indoles from 2-Ethynylanilines and Benzaldehydes.

An efficient synthesis of a variety of 1,2-disubstituted indoles from 2-ethynylanilines was developed. Using 2-ethynylanilines and benzaldehydes as starting materials, the target products (1,2-disubstituted indoles) were obtained smoothly through condensation, reduction, and subsequent cyclization. Various functional groups attached to the aryl ring of 1,2-disubstituted indoles were well tolerated. The protocol features easy performance, easily available starting materials, good yield, and a broad substrate scope, showing potential synthetic value for the preparation of a variety of biologically or pharmaceutically active compounds.

Preparation of a novel composite geopolymer based on calcium carbide slag-fly ash and its characterization, mechanism and adsorption properties.

In this study, a mixed precursor system of fly ash (50 wt%) and calcium carbide slag (50 wt%) was used to prepare a geopolymer, and the hydration and hardening mechanism of the whole system and the microscopic characterization of the calcium carbide-fly ash based polymer were investigated after the addition of calcium carbide slag. Ca(OH)2 in calcium carbide slag can effectively excite the volcanic ash activity of fly ash, which leads to a more adequate geopolymerization reaction and produces more hydrated calcium silicate (C-S-H) gels. These gels have very high specific surface area and surface adsorption energy. The results showed that the specific surface area of geopolymer was as high as 79.76 m2/g, and through the study of its adsorption capacity of Cu(II) in aqueous solution, the results showed that its removal efficiency of Cu(II) was 97.63% and its adsorption capacity was 58.58 mg/g. By using fly ash and calcium carbide slag as the auxiliary raw materials for the preparation of geopolymer, it not only can promote the reaction of proceeding, but can also act as an excellent adsorption material, and also as an effective way to utilize industrial waste resources.

Thermal Mapping of Self-Promoted Calcium Carbide Reactions for Performing Energy-Economic Processes.

The syntheses of various chemical compounds require heating. The intrinsic release of heat in exothermic processes is a valuable heat source that is not effectively used in many reactions. In this work, we assessed the released heat during the hydrolysis of an energy-rich compound, calcium carbide, and explored the possibility of its usage. Temperature profiles of carbide hydrolysis were recorded, and it was found that the heat release depended on the cosolvent and water/solvent ratio. Thus, the release of heat can be controlled and adjusted. To monitor the released heat, a special tube-in-tube reactor was assembled using joining part 3D-printed with nylon. The thermal effect of the reaction was estimated using a thermoimaging IR monitor. It was found that the kinetics of heat release are different when using mixtures of water with different solvents, and the maximum achievable temperature depends on the type of solvent and the amount of water and carbide. The possibility of using the heat released during carbide hydrolysis to initiate a chemical reaction was tested using a hydrothiolation reaction-the nucleophilic addition of thiols to acetylene. In a model experiment, the yield of the desired product with the use of heat from carbide hydrolysis was 89%, compared to 30% in this intrinsic heating, which was neglected.

The use of calcium carbide in food and fruit ripening: Potential mechanisms of toxicity to humans and future prospects.

The global increase in the demand for ripe fruits has induced unhealthy use of toxic chemicals in fruit ripening. One of such chemicals in common use is calcium carbide (CaC2). Due to its nature, commercial CaC2 is consistently found to contain impurities such as Arsenic and other toxic and carcinogenic chemicals. Few studies have only reported acute associative effects of CaC2, whereas there is only sparse evidence of its chronic and long-term impact. This article reviewed all the information on the nature of commercial CaC2 used for food processing. Meanwhile, all reports on the acute effects of CaC2, such as skin burns, skin irritations and inflammation, were summarized. Despite reported acute cases, an increase in commercial CaC2 for fruit ripening has been reported in recent times, especially in developing countries, as many vendors may consider the toxic effects/risks as negligible. Therefore, this study highlighted the paucity in research studies on the chronic impact of commercial CaC2 while proposing possible mechanisms for CaC2 induction of cancer, cardiovascular dysfunction, diabetic mellitus and others. Furthermore, suggestions on further studies to unravel the chronic impacts of CaC2 on health and recommendations for viable alternatives of fruit ripening with minimal or zero toxicity were proffered. Finally, other suggestions such as improving CaC2 detection technologies and innovative grassroots educational programs will strengthen national and international agencies to enforce restrictions on the illicit use of the toxicant for fruit ripening.

Antileishmanial Effects of Acetylene Acetogenins from Seeds of Porcelia macrocarpa (Warm.) R.E. Fries (Annonaceae) and Semisynthetic Derivatives.

As part of our continuous studies involving the prospection of natural products from Brazilian flora aiming at the discovery of prototypes for the development of new antiparasitic drugs, the present study describes the isolation of two natural acetylene acetogenins, (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-yn-19'-enyl)butanolide (1) and (2S,3R,4R)-3-hydroxy-4-methyl-2-(n-eicos-11'-ynyl)butanolide (2), from the seeds of Porcelia macrocarpa (Warm.) R.E. Fries (Annonaceae). Using an ex-vivo assay, compound 1 showed an IC50 value of 29.9 µM against the intracellular amastigote forms of Leishmania (L.) infantum, whereas compound 2 was inactive. These results suggested that the terminal double bond plays an important role in the activity. This effect was also observed for the semisynthetic acetylated (1a and 2a) and eliminated (1b and 2b) derivatives, since only compounds containing a double bond at C-19 displayed activity, resulting in IC50 values of 43.3 µM (1a) and 23.1 µM (1b). In order to evaluate the effect of the triple bond in the antileishmanial potential, the mixture of compounds 1 + 2 was subjected to catalytic hydrogenation to afford a compound 3 containing a saturated side chain. The antiparasitic assays performed with compound 3, acetylated (3a), and eliminated (3b) derivatives confirmed the lack of activity. Furthermore, an in-silico study using the SwissADME online platform was performed to bioactive compounds 1, 1a, and 1b in order to investigate their physicochemical parameters, pharmacokinetics, and drug-likeness. Despite the reduced effect against amastigote forms of the parasite to the purified compounds, different mixtures of compounds 1 + 2, 1a + 2a, and 1b + 2b were prepared and exhibited IC50 values ranging from 7.9 to 38.4 µM, with no toxicity for NCTC mammalian cells (CC50 > 200 µM). Selectivity indexes to these mixtures ranged from >5.2 to >25.3. The obtained results indicate that seeds of Porcelia macrocarpa are a promising source of interesting prototypes for further modifications aiming at the discovery of new antileishmanial drugs.

Synthetic Diphenylacetylene-Based Retinoids Induce DNA Damage in Chinese Hamster Ovary Cells without Altering Viability.

All-trans-retinoic acid (ATRA), the active metabolite of vitamin A, plays a pivotal role in cell differentiation, proliferation and embryonic development. It is an effective therapy for dermatological disorders and malignancies. ATRA is prone to isomerization and oxidation, which can affect its activity and selectivity. Novel diphenylacetylene-based ATRA analogues with increased stability can help to overcome these problems and may offer significant potential as therapeutics for a variety of cancers and neurodegenerative diseases, including amyotrophic lateral sclerosis. Here, we investigated the effects of these retinoids on cell viability and genotoxicity in the widely used model system of the rapidly proliferating Chinese hamster ovary cell line. DC360 is a fluorescent ATRA analogue and DC324 is a non-active derivative of DC360. EC23, DC525, DC540, DC645, and DC712 are promising analogues with increased bioactivity. The cytotoxic activity of the compounds was evaluated by ATP assay and DNA damage was tested by comet assay. No cytotoxicity was observed in the 10-6-10-5 M concentration range. All compounds induced DNA migration similar to ATRA, but DC324, DC360 and EC23 did so to a greater extent, particularly at higher concentrations. We believe that retinoid receptor-independent genotoxicity is a general characteristic of these compounds; however, further studies are needed to identify the molecular mechanisms and understand their complex biological functions.

Solvent-dependent helix inversion in optically active poly(diphenylacetylene)s and their chiral recognition abilities as chiral stationary phases for high-performance liquid chromatography.

We report the first example of solvent-dependent helix inversion in poly(diphenylacetylene) (PDPA) derivatives. Asymmetrically substituted PDPAs bearing optically active substituents linked through amide bonds formed preferred-handed helical conformations because of the optically active substituents in the pendants, whose helix-senses were inverted upon thermal annealing in polar solvents such as N,N-dimethylformamide and dimethylsulfoxide and in nonpolar solvents such as tetrachloroethane. Unlike the solvent-dependent helix inversion reported for other dynamic helical polymers, the macromolecular helicity induced in the polymer backbone of these PDPAs upon thermal annealing was stably maintained at room temperature, independent of the solvent polarity. These diastereomeric PDPAs with opposite helix-senses generated almost mirror-imaged left- and right-handed circularly polarized light in the same solvent at room temperature. Taking advantage of this unique solvent-dependent helix inversion property, the diastereomeric PDPAs with opposite helix-senses were coated on macroporous silica gel and applied to chiral stationary phases for high-performance liquid chromatography. Despite having the same optically active substituents on the pendant phenyl rings, they showed completely different chiral recognition abilities toward many racemates depending on the helix-sense of the polymer backbone, and the elution order of the enantiomers was reversed for some racemates. The combination of the helix-sense of the polymer backbone and the chirality of the pendants, which afforded a higher chiral recognition ability, differed depending on the racemates.

One-Pot Synthesis of 3-Methyl-2-arylimidazo[1,2-a]pyridines Using Calcium Carbide as an Alkyne Source.

An efficient method for the construction of 3-methyl-2-arylimidazo[1,2-a]pyridines from the reactions of calcium carbide, 2-aminopyridines, and aromatic aldehydes is described. The notable advantages for this strategy include the use of an inexpensive and concise solid alkyne source, cheap and readily available raw materials, wide-scope substrates, and a simple work-up procedure.

Redesigning of the cap conformation and symmetry of the diphenylethyne core to yield highly potent pan-genotypic NS5A inhibitors with high potency and high resistance barrier.

Herein, we report the discovery of several NS5A inhibitors with potency against HCV genotype 1b in the picomolar range. Compounds (15, 33) were of extremely high potency against HCV genotype 1b (EC50 ≈ 1 pM), improved activity against genotype 3a (GT 3a) and good metabolic stability. We studied the impact of changing the cap conformation relative to the diphenylethyne core and/or compound symmetry on both potency and metabolic stability. The analogs obtained exhibited improved potency against HCV genotypes 1a, 1b, 3a and 4a compared to the clinically approved candidate daclatasvir with EC50 values in the low picomolar range and SI50s > 7 orders of magnitude. Compound 15, a symmetrically m-, m'-substituted diphenyl ethyne analog, was 150-fold more potent than daclatasvir against GT 3a, while compound 33, an asymmetrically m-, p-substituted diphenyl ethyne analog, was 35-fold more potent than daclatasvir against GT 3a. In addition, compound 15 exhibited a higher resistance barrier than daclatasvir against genotype 1b.

Visualisation of helical structures of poly(diphenylacetylene)s bearing chiral amide pendants by atomic force microscopy.

The helical structures of poly(diphenylacetylene)s bearing optically active substituents linked through amide bonds and with a helicity memory have been visualised using atomic force microscopy. The polymers self-assembled into an ordered 2D monolayer on highly oriented pyrolytic graphite upon exposure to solvent vapour, whose helical pitch and handedness (right- and left-handed) were for the first time directly revealed at molecular resolution.