Presence Of Polyphosphoric Acid Research Articles

Identification of coumarin – benzimidazole hybrids as potential antibacterial agents: Synthesis, in vitro and in vivo biological assessment, and ADMET prediction

The direct-linked coumarin-benzimidazole hybrids, featuring aryl and n-butyl substituents at the N1-position of benzimidazole were synthesized through a Knoevenagel condensation reaction. This reaction involved the condensation of 1,2-diaminobenzene derivatives with coumarin-3-carboxylic acids in the presence of polyphosphoric acid (PPA) at 154 °C. The in vitro antibacterial potency of the hybrid molecules against different gram-positive and gram-negative bacterial strains led to the identification of the hybrids 6m and 6p with a MIC value of 6.25 μg/mL against a gram-negative bacterium, Klebsiella pneumonia ATCC 27736. Cell viability studies on THP-1 cells demonstrated that the compounds 6m and 6p were non-toxic at a concentration of 50 µM. Furthermore, in vivo efficacy studies using a murine neutropenic thigh infection model revealed that both compounds significantly reduced bacterial (Klebsiella pneumonia ATCC 27736) counts (more than 2 log) compared to the control group. Additionally, both compounds exhibited favorable physicochemical properties and drug-likeness characteristics. Consequently, these compounds hold promise as lead candidates for further development of effective antibacterial drugs.

Investigating the anti-aging properties of asphalt modified with polyphosphoric acid and tire pyrolysis oil

Abstract This research focuses on the aging resistance properties of asphalt, which are crucial for determining the lifespan of asphalt pavement. To combat aging, waste tire pyrolysis oil (TPO) is often added to asphalt, enhancing its resistance to aging but compromising high-temperature performance. This study offered a pioneering solution by integrating TPO with polyphosphoric acid (PPA) to address these issues. In this study, we conducted a series of tests to characterize the properties of PPA/TPO modified asphalt, including temperature sweep and bending beam rheometer tests. The results demonstrated that the presence of PPA in the PPA/TPO modified asphalt could improve its high-temperature performance while maintaining its low-temperature properties. Moreover, PPA in the PPA/TPO modified asphalt enhanced the modified asphalt’s resistance to fatigue and deformation during the aging process, while the presence of TPO effectively reduced the impact of thermo-oxidative aging on the modified asphalt during the aging process. Additionally, physicochemical interactions between the base asphalt and modifiers were observed before and after aging. In summary, this study had offered an innovative method to enhance the anti-aging properties of asphalt, and had provided more options for sustainable, environmentally friendly roads.

Effect of Aging on Healing Capacity of Bituminous Composites Containing Polyphosphoric Acid.

This study examines how aging affects the healing capacity of bituminous composites containing polyphosphoric acid (PPA). PPA is commonly used in bituminous composites to enhance its elasticity, however, PPA effectiveness highly depends on other constituents on the matrix and the environmental (internal and external) factors. In terms of internal factors, the interplay between PPA and various bitumen modifiers have been extensively studied. Here, we study how external factors such as exposure to ultraviolet radiation affect PPA's efficacy, measured in terms of change in bitumen's healing index. The study results showed that the introduction of PPA to bituminous composites significantly increases the bitumen healing index, however, the change in the healing index becomes less pronounced as aging progresses. The presence of additives such as taconite were found to affect the effect of PPA on bitumen's healing index. For instance, bitumens containing 30% taconite showed the highest increase in their healing index in the presence of PPA among studied scenarios. Overall, bitumen containing PPA had a higher healing index than those without PPA regardless of the extent of aging and dosage of modifiers. This, in turn, indicates that PPA is highly effective for enhancing bitumen healing. This can be attributed to the role of PPA in promoting intermolecular interactions within the bitumen matrix.

Effects of temperature and age on stress relaxation in straight and modified asphalt binders from a northern Ontario pavement trial

The effects of temperature and age on stress relaxation were investigated for a set of seven asphalt binders from a northern Ontario pavement trial. It was found that between binders, there were rather wide variations for different modes of relaxation. The first peak in the relaxation spectrum, originating from the rapid relaxation within the mobile saturates domains, was relatively insensitive to ageing. The second and third peaks at higher relaxation times changed more with both laboratory ageing and temperature changes. The straight-run Cold Lake asphalt binder showed the least amount of change, and this can likely explain its superior field performance. High styrene–butadiene (SB and SBS) polymer loadings, the presence of polyphosphoric acid (PPA), or re-refined engine oil bottoms (REOB) all resulted in solid-like behaviour, delayed stress relaxation, and associated reduced lifecycles.

Design, synthesis, and molecular docking study of novel cinnoline derivatives as potential inhibitors of tubulin polymerization.

The preparation of a novel 4-methylbenzo[h] cinnolines entity via a three-step synthetic protocol is described. Cyclization of the naphthylamidrazones, in the presence of polyphosphoric acid (PPA), furnishes the respective target benzo[h]cinnolines directly. This one-pot synthesis involves intramolecular Friedel-Crafts acylation followed by instant elimination under heating conditions. It is noteworthy that the yield of the product from this step decreases dramatically if the heating is extended beyond 3h. The target novel cinnolone derivatives were identified by mass spectrometry and their structures elucidated by spectroscopic techniques. Subsequently, molecular docking was performed to shed light on the putative binding mode of the newly synthesized cinnolines. The docking results indicate that these derivatives are potential inhibitors of tubulin polymerization and the best interaction was achieved with a computational ki=0.5nM and posed correctly over the lexibulin.

Synthesis, Charaterization and Bioactivities of Fused Pyrimidobenzothiazol-4-one

Heterocyclic compounds are an important class of basic building blocks, being used by chemists to create compounds of biological or medical relevance. Various heterocyclic building blocks are used in medicinal research, agriculture, and medication discoveries. Considering the significance of heterocyclic ring-containing molecules, 2-amino-6-cyanobenzothiazole is combined with ethylacetoacetate in the presence of polyphosphoric acid to form 8-cyano-2-methyl-4H-pyrimido[2,1-b]benzothiazol-4-one. The structure of the produced chemical is characterised using H1NMR, IR, and mass spectrometry and The synthesized compound successfully showed Biochemical activity against E.Coli, as well as antifungal efficacy against Bacillus subtilis species.

Effect of polyphosphoric acid on fracture properties of asphalt binder and asphalt mixtures

This paper examines the effect of polyphosphoric acid (PPA) on asphalt’s fracture properties. While PPA has been commonly used in the asphalt industry to increase the elasticity and stiffness of asphalt binder, its effects on fracture properties are not thoroughly understood. Fracture as relates to thermal cracking is often associated with asphalt binder rather than a stone skeleton. However, because PPA not only interacts with molecules of asphalt binder but also strongly interacts with stone aggregates due to its highly polar molecules, we hypothesize that the presence of PPA in asphalt will change both bulk and interface properties in asphalt composites, which consequently alter asphalt fracture properties. To test this hypothesis, various PPA dosages (0.5–1.5% wt.) were introduced to the original asphalt binder, and thermo-mechanical and fracture properties of asphalt binder and asphalt mixture were examined. The study results showed that introducing up to 1% PPA enhances the asphalt resistance to fracture; however, excessive PPA weakens the asphalt against cracking. Considering that polar molecules of bitumen supersede others to adsorb to stone aggregate surfaces, the observed weakening effect could be attributed to PPA’s preferential adsorption to stone aggregate surfaces compared to those of asphalt binder. The study outcomes provide insights pertaining to PPA's role and its interplay with other components in asphalt pavements.

Superhydrophobic and phosphorus‑nitrogen flame-retardant cotton fabric

In recent years, various functions including electrical conductivity, superhydrophobicity, magnetism, flame retardancy and antibacterial activity have been considered to allow cotton fabric (CF) a wider the application range. A new strategy for the preparation of superhydrophobic and flame-retardant CF is described here. Phytic acid (PA) and 1-[3-(trimethoxysilyl)propyl]urea (UPTMS) were firstly coated on CF to provide phosphorus‑nitrogen flame retardancy. Then silica particles grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) for the construction of surface roughness and further improvement of flame retardancy and low-surface-energy polydimethylsiloxane (PDMS) were covered on the surface of CF, and the superhydrophobic and flame-retardant CF (SFR-CF) was obtained after thermal curing. The SFR-CF displayed a high water contact angle of 155.9° and excellent anti-adhesion properties and self-cleaning capabilities. In addition, the SFR-CF could be used to efficiently separate oil-water mixtures with a separation efficiency of up to 96.1%. Moreover, the SFR-CF possessed outstanding flame retardancy. The damage length in vertical burning test was only 5.2 cm. This was attributed to not only the release of non-flammable gases such as NH3 and H2O to dilute the concentration of the flammable gas and retard the combustion speed, but also the formation of a dense protective char layer promoted by the presence of poly-phosphoric acid from PA and DOPO-silica. The method used is facile and efficient, and the fabricated superhydrophobic and flame-retardant CF has great potential in a wide range of applications such as oil-pollution treatment, firefighter clothing, outdoor tents and fold-top cars.

Does electrophilic activation of nitroalkanes in polyphosphoric acid involve formation of nitrile oxides?

The mechanistic rationale involving activation of nitroalkanes towards interaction with nucleophilic reagents in the presence of polyphosphoric acid (PPA) was re-evaluated. Could nitrile oxide moieties be formed during this process? This experiment demonstrates that at least in some cases this could happen, as generated nitrile oxides were successfully intercepted as adducts of [3 + 2] cycloadditions.

Preparation of 1,3,4-oxadiazoles and 1,3,4-thiadiazoles via chemoselective сyclocondensation of electrophilically activated nitroalkanes to (thio)semicarbazides or thiohydrazides

Unusual reaction proceeding via the electrophilic activation of nitroalkanes in the presence of polyphosphoric acid has been discovered. Subsequent nucleophilic attack with semicarbazides or thiosemicarbazides allows to access 2-amino-1,3,4-oxadiazoles and 2-amino-1,3,4-thiadiazoles, respectively.

Biocatalytic Synthesis of Moclobemide Using the Amide Bond Synthetase McbA Coupled with an ATP Recycling System.

The biocatalytic synthesis of amides from carboxylic acids and primary amines in aqueous media can be achieved using the ATP-dependent amide bond synthetase McbA, via an adenylate intermediate, using only 1.5 equiv of the amine nucleophile. Following earlier studies that characterized the broad carboxylic acid specificity of McbA, we now show that, in addition to the natural amine substrate 2-phenylethylamine, a range of simple aliphatic amines, including methylamine, butylamine, and hexylamine, and propargylamine are coupled efficiently to the native carboxylic acid substrate 1-acetyl-9H-β-carboline-3-carboxylic acid by the enzyme, to give amide products with up to >99% conversion. The structure of wild-type McbA in its amidation conformation, coupled with modeling and mutational studies, reveal an amine access tunnel and a possible role for residue D201 in amine activation. Amide couplings were slower with anilines and alicyclic secondary amines such as pyrrolidine and piperidine. The broader substrate specificity of McbA was exploited in the synthesis of the monoamine oxidase A inhibitor moclobemide, through the reaction of 4-chlorobenzoic acid with 1.5 equiv of 4-(2-aminoethyl)morpholine, and utilizing polyphosphate kinases SmPPK and AjPPK in the presence of polyphosphoric acid and 0.1 equiv of ATP, required for recycling of the cofactor.

Design, Synthesis, In Vitro Antimicrobial, Antioxidant Evaluation, and Molecular Docking Study of Novel Benzimidazole and Benzoxazole Derivatives

A series of novel 2‐substituted benzimidazole and benzoxazole derivatives as a potential antimicrobial and antioxidant agent were synthesized via coupling of N‐methyl‐o‐phenylenediamine or 2‐amino‐phenol with aromatic aldehyde and acid in the presence of polyphosphoric acid as an efficient catalyst as well as solvent by conventional method in short reaction times with excellent yield. The newly synthesized benzimidazole and benzoxazole derivatives were evaluated for antimicrobial and antioxidant activity and exhibited excellent to good activities compared to the standard drugs. Furthermore, the theoretical predictions based on molecular docking against microbial DNA gyrase could provide an insight into the plausible mechanism of action and establish a link between the observed antimicrobial activity and the binding affinity shedding light on specific thermodynamic (bonded and nonbonded) interactions governing the activity. Furthermore, the synthesized compounds were analyzed for absorption, distribution, metabolism, and excretion properties and exhibited potential properties to build up as good oral drug candidates.

Synthesis and structure of functionalized podands containing 4,7-dihydrotetrazolo[1,5-а]pyrimidine ring. Differently substituted dihydropyrimidine podands

The reaction of 3-oxobutanoate-containing polyethers with benzaldehyde and 5-aminotetrazole in the presence of polyphosphoric acid was used to synthesize podands containing two terminal tetrazolo[1,5-а]dihydropyrimidine groups. Byproducts were isolated and identified as podands containing different substituents – one 4,7-dihydrotetrazolo[1,5-а]pyrimidine ring system and a free hydroxy group at the other terminus of the polyether chain. Analogous differently substituted podands, including one 3,4-dihydropyrimidine-2(1H)-thione moiety, were isolated from the reactions of 3-oxobutanoate-containing polyethers with benzaldehyde and thiourea.

New One-Pot Synthesis of Polysubstituted Benzofurans and Benzo-1,4-dioxines

It has been revealed that the copper(II) triflate catalyzed reaction of ethyl-2-diazo-3-oxobutanoate with phenols followed by cyclization of the intermediate enol in the presence of polyphosphoric acid is a simple and efficient method of synthesis of polysubstituted benzofurans. The use of pyrocatechol leads to the corresponding substituted 1,4-benzodioxine-2-carboxylates as major products.

Modification of thermal and rheological behavior of asphalt binder by the addition of an ethylene-methyl acrylate-glycidyl methacrylate terpolymer and polyphosphoric acid

Abstract This study evaluated the modification effects of adding ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMGMA) in the presence of polyphosphoric acid (PPA) to an asphalt binder graded as 50/70 (0.1mm) in the Brazilian penetration grade specification (AC 50/70). The EMGMA terpolymer has been presented as a new alternative to modify asphalt binders properties, as scientific literature is scarce on its usage in this context and also on the role of PPA when used in combination with reactive polymers. The characteristics of the modified binder were analyzed by standard and rheological testing, including Multiple Stress Creep Recovery test (MSCR) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The MSCR test showed that the modified binder presented lower values of non-recoverable compliances (Jnr) and a higher percent recovery, when compared to the conventional binder. This behavior indicates that addition of EMGMA and PPA in asphalt binders could enhance the resistance to rutting of asphalt mixtures. The statistical evaluation showed that EMGMA had greater influence on the studied properties of Jnr (0.1kPa), MSCR recovery, softening point and elastic recovery at 25°C and that the PPA had also significant influence on these properties. FTIR analysis showed that chemical reactions occurred between the asphalt binder and EMGMA, forming a three-dimensional polymeric network, which promotes improved characteristics.

Electrophilically activated nitroalkanes in the synthesis of 6,7-dihydro-1H-cyclopenta[g]perimidines

A highly efficient synthetic route to 6,7-dihydro-1H-cyclopenta[gh]perimidines has been proposed on the basis of a novel reaction of nitroalkanes with 4,5-diaminoacenaphthene in the presence of polyphosphoric acid. The reaction involves phosphorylation of the aci-nitro compound, followed by intramolecular cyclization.

(Invited) High Temperature Membrane Electrode Assemblies for Intermediate Temperature Fuel Cells: Past, Present, and Future

Fuel cells that operate between approximately 150 oC and 250 oC accrue certain advantages, most notably facilitated operation with low grade / low cost hydrogen sourced from carbon feedstocks, robust cathode performance in the presence of air contaminants, absence of balance of plant components for stack water management, high quality heat, and readily sourced materials of construction. Fuel cells running at these intermediate temperatures with phosphoric acid as the electrolyte currently hold the record for a commercial lifetime warrantee (1). Yet, lower temperature polymer electrolyte fuel cells (PEFC) operating at under 100 oC and comprised of a conductive membrane, electrodes, and gas diffusion layers offer the potential for low cost assembly at high volumes, especially if these components are made in roll-to-roll processes. The better of these two technologies would be a hybrid high temperature Membrane Electrode Assembly (MEA) based on phosphoric acid electrolyte. The first hybrid high temperature (HT) MEA made use of polybenzimidazole (PBI) as a membrane matrix for phosphoric acid and originated from the Case Western Reserve University team of Litt, Savinell and Wainright in the early 1990s as part of a research proposal to the Defense Advanced Research Projects Agency (DARPA). Their initial motivation was to develop a system that could overcome the limitations of direct methanol oxidation at under 100 oC (2). Although ultimately not viable for direct methanol oxidation, hydrogen oxidation with 1-2 % CO proved good enough to license the technology to PEMEAS, the company that developed the first commercial PBI HT MEA based on pre-formed membranes of PBI. However, using a preformed PBI membrane posed some limitations on acid content, and through the efforts of Calundann and Benicewicz, a second generation PBI membrane was invented (3). This new process identified a technique to polymerize PBI in the presence of polyphosphoric acid (PPA), and then hydrolyze the cast film to phosphoric acid (PA). The change of solvent from PPA to PA also radically changed the morphology of the PBI from a viscous solution into a tough second generation PBI plastic that held over 90 % by weight PA. This development also radically simplified the construction of HT MEAs by eliminating the acid soaking step. Due to the nature of these materials, new gas diffusion electrode architectures were developed and optimized to accommodate a membrane-electrode interface substantially different than that found in LT MEA assemblies. This electrode effort on roll coaters was awarded a Department of Energy Manufacturing R&D award (4). Ultimately, BASF purchased PEMEAS, as well as the electrode team at PEMEAS. In parallel to the development of the polybenzimidazole (PBI) system, Advent Technologies identified and developed a pyridine polymer based TPS® system also using PA imbibed into the membrane matrix. Advent’s TPS membranes operate over a wide temperature range from ~120 °C to greater than 200 °C. In 2014, Advent became the licensee of BASF’s PBI MEA and gas diffusion electrode technology. Advent develops, manufactures, and markets both the PBI and TPS MEAs. This presentation will present an overview of the commercial and technical history of developing HT MEAs, including some of the latest membrane advances like the third generation PBI MEAs, and cross-linked TPS MEAs operating at 210 oC, and conclude with future directions such as the application of HT MEAs in facilitating direct oxidation of dimethyl ether (DME). http://www.doosanfuelcell.com/en/main.doRobert F. Savinell and Jesse Wainright, "Overture: The Early History of PBI/Phosphoric acid membranes," in High Temperature Polymer Electrolyte Membrane Fuel Cells: Approaches, Status and Perspectives, edited by Qingfeng Li, David Aili, Hans Aage Hjuler and Jens Oluf Jensen, Spring International Publishing, 2016.For example, G. Calundann et al. US Patent 7,820,314.US Department of Energy Annual Merit Review, 2013.

Synthesis of Novel Indole-Benzimidazole Derivatives

2-Methylindole-3-acetic acid and its 5-methoxy derivative were prepared from the respective phenylhydrazines and levulinic acid. Indole-3-carboxylic acid was obtained from indole, dimethylformamide and trifluoroacetic acid. These indole carboxylic acids were then condensed with substituted o-phenylenediamines under high temperature conditions in the presence of polyphosphoric acid as a catalyst to give the combined indole-benzimidazoles.

Design and application of tri-benzimidazolyl star-shape molecules as fluorescent chemosensors for the fast-response detection of fluoride ion

Three tri-benzimidazolyl star-shape molecules have been successfully designed and applied as new fluorescent chemosensors for the detection of fluoride ion for the first time. They are easily obtained by the simple condensation of o-phenylenediamines and trimesic acid in the presence of polyphosphoric acid as catalyst. Three chemosensors show good selectivity, high sensitivity, and fast response toward F−. The addition of fluoride ion to the chemosensors causes a dramatically observable colour change from blue to light cyan not only in solution, but also in solid state under UV light. 1H NMR and DFT calculations studies confirm that the F− ion facilitates its recognition due to the formation of NH⋯F hydrogen bond and subsequent deprotonation as designed. In addition, chemosensors 3 can be reversible and reusable for sensing fluoride ion, resulting that they can be developed as an IMPLICATION type logic gate at molecular level. Moreover, these chemosensors have also been successfully applied to the detection of fluoride ion from inorganic origin and commercial toothpaste sample.

SYNTHESIS AND ANTIOXIDANT ACTIVITY OF THE 2-METHYL BENZIMIDAZOLE

2-methyl benzimidazole is a heterocyclic organic compound having an important pharmacophoric group which is used in medicinal industry. o- Phenyldiamine was treated with acid in the presence of polyphosphoric acid and other solvents. The presence of specific group was determined by FTIR spectroscopy. The obtaining compound was screened by the antioxidant activity by using the DPPH method. Key words- 2- methyl benzimidazole, o- phenyldiamine, antioxidant activity, DPPH method.