Strong Basic Conditions Research Articles

Extending the S-benzimidazolyl (SBiz) platform: N-alkylated SBiz glycosyl donors with the universal activation profile.

This article describes the development of alkylated S-benzimidazolyl (SBiz) imidates as versatile building blocks for chemical glycosylation. The SBiz imidates have been originally developed as a new platform for active-latent glycosylations and its utility was further extended to other common strategies for oligosaccharide synthesis. This article expands upon the utility of these compounds. We developed a general protocol for the synthesis of a series of N-alkylated SBiz glycosides from N-protected SBiz aglycones by Lewis acid-mediated coupling with glucose pentaacetate. The N-alkylated SBiz moiety was found to be stable under strong basic conditions which allowed us to obtain both armed and disarmed N-alkylated SBiz donors. These donors showed good reactivity at a variety of activation conditions, and generally provided high yields in glycosylations.

Development of Silver Based Catalysts Promoted by Noble Metal M (M = Au, Pd or Pt) for Glycerol Oxidation in Liquid Phase

The liquid-phase oxidation of glycerol was studied to obtain glycolic acid as a value-added molecule. The effect of metal addition to silver based catalyst was investigated under strong basic condition. The best catalytic performance was obtained over silver catalyst promoted with a small amount of platinum Ag95–Pt5/CeO2. Namely, the conversion close to 54% was reached after 5 h of reaction at 60 °C, with the selectivity to glycolic acid of 51%. Further increase in the amount of promotor (up to 50%) changed the reaction mechanism to product selectively the glyceric acid.

The detection of copper ions based on photothermal effect of cysteine modified Au nanorods

The cysteine (CYS)-stimulated aggregation of Au nanorods (NRs) is used as an auxiliary reporting system for the optical detection of copper ions. CYS-Au NRs show end-to-end and side-by-side assembly at strong acidic and basic condition, and corresponding LSPR peaks shift to red or blue. However, Cu2+ can readily induce the end-to-end assembly of CYS-Au NRs based on the coordination between Cu2+ and CYS at weak acidic condition (pH 5). The assembly of Cu2+-CYS-Au make the decrease of LSPR peak at 800nm and appear a new peak at 1050nm, which reduce their photothermal conversion efficiency under 808nm laser irradiation. The different photothermal conversion efficiency has relation with the temperature change of Au NRs solution. So, a new nanosensor for detecting Cu2+ is developed based on the varied photothermal effect. Different from colorimetric detection for Cu2+, the sensor of photothermal effect is more sensitive to low concentration of Cu2+. It shows high sensitivity and selectivity. Here, the detection limit for Cu2+ is 5nM.

Reversible Absorption and Emission Responses of Nile Blue and Azure A Derivatives in Extreme Acidic and Basic Conditions.

Oxazinium derivatives have recently played an important role in bioanalysis attributing to the distinguished properties, thus a detailed study of the structure-property relationship is especially significant. Herein, pH-sensitive optical properties of Nile Blue (1a), N-monoalkyl-Nile Blue (1b) and Azure A (1c) have been carried out in extreme acid and base conditions. Dyes 1a and 1c showed colorimetric changes by the protonation of nitrogen atom in strong acidic condition (pH<2.0), and dyes 1a-c exhibited colorimetric changes by equilibrium between amino and imide groups in very strong basic case (pH>7.6). Besides, their fluorescent properties were closed to ON-OFF and OFF-ON emissions at 640-820nm under strong acidic and basic conditions. Moreover, the absorption and emission properties were reversible, and there were no remarkable optical intensity changes of dyes 1a-c under subacidic and neutral solutions (pH=3.0-7.0). The (TD) DFT calculations were used to optimize the most stable structures of their corresponding protonated and deprotonated forms, and their absorption and emission properties were also explained. Their fluorescent properties nearly ON-OFF and OFF-ON in strong acidic and basic conditions at near-infrared region will give the possible application in pH detection for extreme conditions. Graphical abstract ᅟ.

Facile Synthesis of Co3O4 with Different Morphologies via Oxidation Kinetic Control and Its Application in Hydrogen Peroxide Decomposition

Co3O4 nanoparticles (NPs) with tubular and hollow structures were successfully synthesized by the formation of CoOOH and subsequent high-temperature calcination in air. The as-synthesized Co3O4 retained the morphologies of CoOOH. Therefore, the key step for the synthesis of Co3O4 was the controllable preparation of CoOOH NPs with tubular and hollow structures, which were prepared through a facile strategy involving the oxidation of β-Co(OH)2 under strong basic conditions (template-free, aqueous solution, and mild temperature). The morphology of CoOOH was tuned by employing air and H2O2 as the oxidizing agents which possessed different oxidation abilities and thus resulted in different oxidation kinetics. The plausible formation mechanism of CoOOH NPs with tubular and hollow structures was both related to the Kirkendall effect. In contrast to the commercial Co3O4, the as-prepared Co3O4 NPs with tubular and hollow structures showed superior catalytic activities for the decomposition of H2O2. The reaction ra...

Reversible Hydrolysis Reaction with the Spore Photoproduct under Alkaline Conditions.

DNA lesions may reduce the electron density at the nucleobases, making them prone to further modifications upon the alkaline treatment. The dominant DNA photolesion found in UV-irradiated bacterial endospores is a thymine dimer, 5-thyminyl-5,6-dihydrothymine, i.e., the spore photoproduct (SP). Here we report a stepwise addition/elimination reaction in the SP hydrolysis product under strong basic conditions where a ureido group is added to the carboxyl moiety to form a cyclic amide, regenerating SP after eliminating a hydroxide ion. Direct amidation of carboxylic acids by reaction with amines in the presence of a catalyst is well documented; however, it is very rare for an amidation reaction to occur without activation. This uncatalyzed SP reverse reaction in aqueous solution is even more surprising because the carboxyl moiety is not a good electrophile due to the negative charge it carries. Examination of the base-catalyzed hydrolyses of two other saturated pyrimidine lesions, 5,6-dihydro-2'-deoxyuridine and pyrimidine (6-4) pyrimidone photoproduct, reveals that neither reaction is reversible even though all three hydrolysis reactions may share the same gem-diol intermediate. Therefore, the SP structure where the two thymine residues maintain a stacked conformation likely provides the needed framework enabling this highly unusual carboxyl addition/elimination reaction.

Evaluation of leaching characteristics of heavy metals from municipal solid waste incineration fly ash by up-flow percolation column tests

To determine the potential release of heavy metals from municipal solid waste incineration fly ash (MSWI-FA), the leaching behaviors of MSWI-FA from Likeng waste incineration power plant in China were characterized according to the US EPA method 1314. Heavy metals (i.e. Pb, Cr, Cd, Cu and Zn) leaching characteristics were investigated over a wide range of liquid-to-solid ratios (L/S 0.2–10 mL/g-dry) and different pH conditions (2, 4 and 6). The test results revealed that eluent with high pH of about 12 increased a little with increase of influent solutions pH. Similar concentration patterns of a heavy metal were observed at different pH influent solutions, and different concentration patterns for different heavy metals were showed at different liquid-to-solid ratio (L/S) range. Cumulative maximum release of heavy metals followed the pattern of Cr > Pb > Cu > Cd > Zn. The release of Pb and Cd decreased with pH of influent solutions while Cu and Zn changed oppositely. However, concentration of Cr did not significantly change and cumulative release linearly increased with L/S due to the leaching process was controlled by solubility. The effect of L/S ratio on Pb, Cd and Cu release in MSWI-FA indicated the prevalence of the dominant mechanism was either solubility or diffusion controlled. Zn extract concentrations were observed to decrease initially with L/S increase to 5 followed by a slight increase due to the presence of soluble zinc compounds in strong basic conditions.

Structure and Long-Term Stability of Alkylphosphonic Acid Monolayers on SS316L Stainless Steel.

Surface modification of stainless steel (SS316L) to improve surface properties or durability is an important avenue of research, as SS316L is widely used in industry and science. We studied, therefore, the formation and stability of a series of organic monolayers on SS316L under industrially relevant conditions. These included acidic (pH 3), basic (pH 11), neutral (Milli-Q water), and physiological conditions [10 mM phosphate-buffered saline (PBS)], as well as dry heating (120 °C). SS316L was modified with alkylphosphonic acids of chain length (CH2)n with n varying between 3 and 18. While alkylphosphonic acids of all chain lengths formed self-assembled monolayers with hydrophobic properties, only monolayers of chain lengths 12-18 formed ordered monolayers, as evidenced by static water contact angle (SCA), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and infrared reflection absorption spectroscopy (IRRAS). A long-term stability study revealed the excellent stability of monolayers with chain lengths 12-18 for up to 30 days in acid, neutral, and physiological solutions, and for up to 7 days under dry heating. Under strong basic conditions a partial breakdown of the monolayer was observed, especially for the shorter chain lengths. Finally, the effect of multivalent surface attachment on monolayer stability was explored by means of a series of divalent bisphosphonic acids.

Communication—Anion-Conductive Perfluoroheteroaromatic Composite Membranes: High Chemical Stability under Strong Alkaline Conditions

Nafion is used as cation-conductive fluoropolymeric membranes in proton-exchange membrane fuel cells, flow batteries, etc. However, its fluoropolymer-based anion-exchange counterparts that are stable under strong basic conditions of alkaline membrane fuel cells have not yet been documented. In this communication, we report a fluoropolymer-based anion-conductive membrane comprised of perfluoro(phenyl-2,2′:6′,2″-terpyridine), 2,2′:6′,2″-terpyridine, and ZrO(ClO4)2, which was found stable in a 7 M KOH solution at 120°C for >2,200 h—unprecedented in literatures. Such high stability is due to its fluorinated polymeric structure, covalent C-C bonds that link the polymer side chains and the heteroaromatic ligands, and ZrO(ClO4)2 nanoclusters as anion-exchange groups.

Stable Tricyclic Antitubercular Ozonides Derived from Artemisinin.

New, highly stable tricyclic antitubercular ozonides 9 and 10 derived from artemisinin are reported in 39 and 9% yields, respectively. The ozonide groups of 9 and 10 were found to be stable under strong basic and acidic conditions. The absolute configuration of ozonides 9 was confirmed by X-ray crystallography. Ozonide 10 shows promising antitubercular activity against M. tuberculosis H37Ra and M. tuberculosis H37Rv with MIC values of 0.39 and 3.12 μg/mL, respectively.

Effect of pH on the stability and molecular structure of nitrosyl hemochromogen

This study explored the effect of pH on the stability and molecular structure of nitrosyl hemochromogen (NO-Heme) using ultraviolet (UV), electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopy. The NO-Heme was extracted from pre-cooked cured beef and was dissolved in an 80% acetone solution pre-adjusted to different pH values with 2mol/L HCl and 2mol/L NaOH. The results show that pH significantly influences the optical properties and stability of NO-Heme. Strong acidic and weak basic conditions favor the red stability of NO-Heme. The conjugate structure of NO-Heme changed under strong basic conditions, as the NO− group was shown to be still associated with the iron porphyrin, but the color of NO-Heme changed from pink to yellow. NO-Heme is extremely unstable at weakly acidic pH, and this may be the why pH affects the apparent color of cured meat products during storage.

Jacket-free stir bar sorptive extraction with bio-inspired polydopamine-functionalized immobilization of cross-linked polymer on stainless steel wire

Stainless steel wire (SSW) is a good substrate for stir bar sorptive extraction (SBSE). However, it is still a challenge to immobilize commonly used cross-linked polymers onto SSW. In this work, we present a new approach for immobilization of the cross-linked organic polymer onto SSW for jacket-free SBSE. A dopamine derivative was firstly synthesized; by introducing a mussel-inspired polydopamine process, a stable coating layer was finally generated on the surface of SSW. Secondly, the cross-linked polymer was synthesized on the polydopamine-modified SSW by using acetonitrile as the porogen, acrylamide (AA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker and 2,2′-azobis (2-methylpropionitrile) as the initiator. A diluted pre-polymerization solution was carefully prepared to generate a thin layer of the polymer. The prepared poly(EGDMA-AA)-modified stir bar showed high stability and good tolerance toward stirring, ultrasonication, organic solvents, and strong acidic and basic conditions. Morphology and structure characterization of coatings were performed by scanning electron microscopy and Fourier transform infrared spectra, respectively. The prepared poly(EGDMA-AA)-modified stir bar showed great extraction efficiency toward protoberberines, with enrichment factors of 19–42. An SBSE-HPLC method was also developed for quantitative analysis of protoberberines. The method showed low limits of detection (0.06–0.15ngmL−1), wide linear range (0.5–400ngmL−1), good linearity (R≥0.9980) and good reproducibility (RSD≤3.60% for intra-day, RSD≤4.73% for inter-day). The developed method has been successfully applied to determine protoberberines in herb and rat plasma samples, with recoveries of 88.53–114.61%.

Photocatalytic hydrogen generation from water–methanol mixtures using “black” anatase obtained by annealing of titanate nanotubes

Digestion for an extended period of a commercial nanoparticulated TiO2 sample under strong basic conditions (10M NaOH) leads to the formation of titanate nanotubes with long aspect ratio. The most remarkable observation was the appearance of light-brown colour in the titanate sample that is reflected in the presence for this titanate nanotube sample of a continuous absorption in the visible region decreasing in intensity towards the red. Titanate nanotubes were annealed under hydrogen atmosphere at 350 and 500°C. The last temperature leads to the reconstitution of anatase phase and an increase in the intensity of the black colour. The photocatalytic activity of the set of titanium samples was tested for hydrogen generation from water–methanol mixtures under monochromatic visible light (532nm) or UV light (355nm) or under simulated sunlight. It was determined that the most active sample in all conditions was the one that after NaOH digestion was submitted to hydrogen annealing at 500°C. This sample exhibits even higher activity than that observed for “black” titania prepared as previously reported by direct treatment of nanoparticulated TiO2 with H2 without NaOH digestion.

Sonochemical Synthesis of Hematite Nanoparticles

Hematite nanoparticles were prepared by a procedure consisting in sonication of μ3-oxo trinuclear iron(III) acetate of composition [Fe3O(OOCCH3)6(H2O)3]NO3∙4H2O, {Fe3O}NO3 as iron source, in strong basic conditions followed by thermal treatment at 600 C. The formation of the hematite was confi rmed by IR spectroscopy, X-ray powder diffraction and Raman spectroscopy while, the shape and size of the nanoparticles and their agglomeration were evidenced and estimated on the basis of the images taken with TEM techniques.

Nano-graphene oxide carboxylation for efficient bioconjugation applications: a quantitative optimization approach

A method for carboxylation of graphene oxide (GO) with chloroacetic acid that precisely optimizes and controls the efficacy of the process for bioconjugation applications is proposed. Quantification of COOH groups on nano-graphene oxide sheets (NGOS) is performed by novel colorimetric methylene blue (MB) assay. The GO is synthesized and carboxylated by chloroacetic acid treatment under strong basic condition. The size and morphology of the as-prepared NGOS are characterized by scanning electron microscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effect of acid to base molar ratio on the physical, chemical, and morphological properties of NGOS is analyzed by Fourier-transformed infrared spectrometry (FTIR), UV–Vis spectroscopy, X-ray diffraction (XRD), AFM, and zeta potential. For evaluation of bioconjugation efficacy, the synthesized nano-carriers with different carboxylation ratios are functionalized by octaarginine peptide sequence (R8) as a biomolecule model containing amine groups. The quantification of attached R8 peptides to graphene nano-sheets’ surface is performed with a colorimetric-based assay which includes the application of 2,4,6-Trinitrobenzene sulfonic acid (TNBS). The results show that the thickness and lateral size of nano-sheets are dramatically decreased to 0.8 nm and 50–100 nm after carboxylation process, respectively. X-ray analysis shows the nano-sheets interlaying space is affected by the alteration of chloroacetic acid to base ratio. The MB assay reveals that the COOH groups on the surface of NGOS are maximized at the acid to base ratio of 2 which is confirmed by FTIR, XRD, and zeta potential. The TNBS assay also shows that bioconjugation of the optimized carboxylated NGOS sample with octaarginine peptide is 2.5 times more efficient compared to bare NGOS. The present work provides evidence that treatment of GO by chloroacetic acid under an optimized condition would create a functionalized high surface area nano-substrate which can be used for subsequent efficient bioconjugation applications.

An unexpected deamination reaction after hydrolysis of the pyrimidine (6-4) pyrimidone photoproduct.

Pyrimidine (6-4) pyrimidone photoproduct (6-4PP), a common DNA photolesion formed under solar irradiation, was indicated to hydrolyze under strong basic conditions, breaking the N3–C4 bond at the 5′-thymine. The reanalysis of this reaction revealed that the resulting water adduct may not be stable as previously proposed; it readily undergoes an esterification reaction induced by the 5-OH group at 6-4PP to form a five-membered ring, eliminating a molecule of ammonia.

Superhydrophobic mesoporous material as a pH-sensitive organic dye adsorbent

A superhydrophobic material was synthesized using a one-pot approach via the self-hydrolysis and condensation of polymethylhydrosiloxane (PMHS) under a base catalyst in ethanol and water media. The obtained superhydrophobic polymethylhydroxysiloxane (PMHOS) material was stable up to temperatures as high as 500°C, even under strong acidic and basic pH conditions. The micro–nano particles of PMHOS exhibited a hierarchical morphology with a mesoporous structure. The superhydrophobic PMHOS, however, become superhydrophilic by calcination at 600°C. The superhydrophobic and superhydrophilic PMHOS exhibited a good ability to adsorb organic dyes at a certain pH (pH 12).

PH-dependent magnetic phase transition of iron oxide nanoparticles synthesized by gamma-radiation reduction method

In this study, the influence of pH variation on structural and magnetic phase transition of gamma radiolytic synthesized iron oxide nanoparticles is investigated. The structure and magnetic properties of irradiated samples are characterized using X-ray diffraction, Fourier transfer infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometer. It was found that, in acidic irradiated solution, Fe3+ ions make various complexes with polyvinyl alcohol and water molecules which exhibit a multiphase magnetic property as a mixture of dia and paramagnetic materials. On the other hand, in basic condition, rate of radiation induced reduction of Fe3+ ions increased which leads to the formation of superparamagnetic Fe3O4 nanoparticles. By increasing pH value, in strong basic condition, the tendency of paramagnetic iron (III) oxy-hydroxide formation was high compared to other phases. This variation in the magnetic properties was explained based on iron ions reduction mechanism and the variation of the ligands’ properties during formation of nanoparticles under irradiation.

Investigations on the degradation of aspartame using high-performance liquid chromatography/tandem mass spectrometry

Abstract Aspartame is a widely used sweetener, the long-term safety of which has been controversial ever since it was accepted for human consumption. It is unstable and can produce some harmful degradation products under certain storage conditions. A high-performance liquid chromatography/tandem mass spectrometry method was developed for the simultaneous analysis of aspartame and its four degradation products, including aspartic acid, phenylalanine, aspartyl-phenylalanine and 5-benzyl-3,6-dioxo-2-piperazieacetic acid in water and in diet soft drinks. Aspartame and its four degradation products were quantified by a matrix matched external standard calibration curve with excellent correlation coefficients. The limits of detection were 0.16–5.8 μg/L, which exhibited higher sensitivity than common methods. This method was rapid, sensitive, specific and capable of eliminating matrix interferences. It was also applied to the study of the degradation of aspartame at various pH and temperatures. The results indicated that aspartame was partly degraded under strong acidic or basic conditions and the extent of degradation increased with increasing temperature.

Linear or Cyclic Clusters of Cu(II) with a Hierarchical Relationship

The polydentate ligand 2,6-bis(5-(2-hydroxyphenyl)-pyrazol-3-yl)-pyridine, H4L, exhibits a series of coordination pockets favoring the establishment of metal sequences with predetermined motifs, together with a degree of flexibility for the formation of clusters with various overall topologies. With Cu(II) under strong basic conditions it has a marked tendency to stabilize a cyclic [Cu16L8] cluster. The sequential formation of this compound via [Cu7L8](2-) intermediates, recognized in its structure, is suggested by crystallographic evidence, which shows the persistent formation of the complex salt (NBu4)2[Cu7L8] in the presence of the organic cation. Also, the crystallographic identification of the related cluster [Cu11L5(OH)2(py)12] from similar reaction conditions underscores the rich multiplicity of species attainable from this simple reaction system.