824-78-2

Two picolinamide-based zinc(II) coordination polymers {[Zn(SO 4)(3-bpit) (CH3OH)2]·2CH 3OH}n (1)(3-bpit = N,N'-bis(3-pyridylformyl)imidazolidine- 2-thione) and [Zn(SCN)2(4-bpit)]n(2) (4-bpit = N,N'-bis(4-pyridylformyl)imidazolidine -2-thione) have been synthesized and structurally characterized. In complexes 1 and 2, the picolinamide-based ligands, 3-bpit and 4-bpit, function as bridging bidentate mode, leading to polymeric structures. Complex 1 is a two-dimensional coordination polymer while 2 exhibits a one-dimensional chain structure. The hydrolysis of 4-nitrophenyl acetate catalyzed by complexes 1 and 2 under mild conditions was also investigated.

Controlling the structure, morphology, and composition of noble metals is of great significance to improve the catalytic activity and stability of catalysts. Herein, we have successfully synthesized self-interconnecting Pt-Cu alloy nanowire networks (NWNs) with controllable compositions via the co-reduction of the metal precursors potassium chloroplatinate (K2PtCl6) and CuCl2 with sodium borohydride (NaBH4). Owing to the hydrogen bubbles formed by NaBH4 hydrolysis and oxidation as a dynamic template, the facile strategy was carried out without any organic solvent, capping agent, polymer, or special experimental device, ensuring that the surfaces of NWNs were definitely “clean”. The performance of the as-prepared Pt-Cu alloy NWNs for the reduction of 4-NP was dramatically improved compared with that of pure Pt NWNs and the commercial Pt/C catalyst. Particularly, the PtCu NWNs with a Pt/Cu atomic ratio of 1?:?1 exhibited excellent catalytic activity and reusability for the reduction of toxic 4-NP. The reaction rate constant and activity factor of the PtCu NWNs reached 1.339 × 10?2 s?1 and 66.95 s?1 g?1, respectively, which were dramatically better than those of pure Pt NWNs (11.5-fold) and commercial Pt/C (13-fold). The superior catalytic activity and reusability can mainly be attributed to the clean surface, the synergistic effect of Cu and Pt atoms and the self-interconnecting nanowire network structure.

We report on a bottom up approach for the synthesis of a Pd-polypyrrole nanocomposite material. The composite material was characterized by means of different techniques, such as UV-vis, IR, and Raman spectroscopy, which offered information about the chemical structure of the polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the polymer matrix. During the synthesis of the nanocomposite, the Pd nanoparticles act as a catalyst for a model proton-coupled electron transfer reaction. The Pd-polypyrrole nanocomposite material was also used as a catalyst for the electro-catalytic detection of tryptophan, a precursor for some neurotransmitters. This journal is the Partner Organisations 2014.

A series of thiocyanato-bridged heterometallic coordination polymers with a 3D reticular network have been synthesised by the reaction of [PtIV(SCN)6]2- with MII ions to form {MII[PtIV(SCN)6]}n and {[MII(CH3OH)2][PtIV(SCN)6]}n (MII = MnII, FeII, CoII, NiII or CuII) in water and methanol, respectively. Single-crystal X-ray analyses revealed the absence of open metal sites in {MII[PtIV(SCN)6]}ns and the formation of potential open metal sites at the MII ions of {[MII(CH3OH)2][PtIV(SCN)6]}ns by the coordination of methanol. One of the two coordinating methanol molecules in {[CoII(CH3OH)2][PtIV(SCN)6]}n was replaced with pyridine to stabilise the open metal sites, because the methanol molecules are too labile to maintain open metal sites in water. The heterogeneous catalysis of coordination polymers with and without open metal sites was examined for organophosphate hydrolysis and photocatalytic water oxidation to clarify the requisites for heterogeneous catalysts.

The α-deuterium secondary kinetic isotope effect for the uncatalysed hydrolysis of 2-(p-nitrophenoxy)tetrahydropyran is 1.17 in water (46 deg C), a result which is very similar to values for the solvolysi of simple secondary alkyl arenesulfonates which proceed with rate-limiting ionization and appreciably higher than results for enzyme-catalysed hydrolysis of other acetals.

A change in the reactivity of ethyl p-nitrophenyl chloromethylphosphonate in the sodium bis(2-ethylhexyl)sulfosuccinate-n-nonane-water system around the percolation threshold was found. Study of location sites of the reactants by NMR self-diffusion and optical spectroscopy and modeling of the kinetic data in terms of the pseudophase approach demonstrated that below the percolation threshold, the reaction occurs in the surface layer. The observed rate constant for substrate hydrolysis in a microemulsion below the percolation threshold is described by the Arrhenius equation, like that in aqueous solutions. Above the percolation threshold, the slope of the Arrhenius plot sharply changes, which is apparently due to a change in the reactant location pattern and, hence, the microscopic properties of the medium in the region of their solubilization.

The alkaline hydrolysis reaction of O-(4-cyanophenyl), O-(4-methylphenyl), and phenyl O-(4-nitrophenyl) thionocarbonates (1, 2, and 3, respectively) and O-(4-cyanophenyl) and phenyl O-(4-nitrophenyl) carbonates (4 and 5, respectively) has been spectrophotometrically studied in aqueous borate buffer media, in the presence of the cationic surfactant CTAB. The pseudophase model successfully explained the results obtained, in the presence of this cationic micelle, and various kinetic parameters were determined. Results show that the catalytic efficiency increases in carbonates and thionocarbonates. In fact, a catalytic efficiency ( kobsmax/k'w) of 485-fold was found in the hydrolysis reaction of thionocarbonate 1, while in the carbonate homolog 4, the effect was of 146-fold. In addition, we found that at the same experimental conditions (Borate buffer pH = 9.0 and 25°C), an increase in the concentration of the buffer led to a decrease of the hydrolysis rate.

The reaction of p-nitrophenyldiethylphosphate with sodium phenolate takes place readily in aprotic polar solvents.Bimolecular rate constants of this reaction increase with increased concentration of the phenolate in such solvents as dimethylsulfoxide (DMSO), dimethylformamide (DMF), or hexamethylphosphoric amide (HMPA), but decrease in acetonitrile or acetone; this is caused by the association of sodium phenolate, and the different reactivities of free ions and ion pairs.The addition of 18-crown-6 to the reaction mixture decreases the reaction rate, because of the reduced reactivity of the complex formed by the crown ether with the phenolate ion pair.

A facile method for one-step synthesis of size-controlled gold nanoparticles (AuNPs) supported on collagen fiber (CF) at room temperature was proposed. Epigallocatechin-3-gallate (EGCG), a typical plant polyphenol, was grafted onto CF surface to serve as reducing/stabilizing agent, so that the AuNPs were generated on CF surface without introduction of extra chemical reagents or physical treatments. The prepared AuNPs were fully characterized, and the results showed that the dispersed AuNPs were successfully produced and the mean particle size of AuNPs could be effectively controlled in range of 18 to 5 nm simply by varying the grafting degree of EGCG on CF surface. These stabilized AuNPs were found to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol in aqueous phase. The catalytic behaviors of AuNPs depended on the particle size and the grafting degree of EGCG. A distinct advantage of these catalysts is that they can be easily recovered and reused at least twenty times, because of the high stability of the AuNPs supported by EGCG-grafted CF. The Royal Society of Chemistry.

Diastereomeric phosphotriesters 1 and 2 are rapidly cleaved by micellar iodosobenzoate, iodosonaphthoate, and cetyltrimethylammonium hydroperoxide; diastereoselectivity is modest.

The invention discloses a synthesis process of sodium p-nitrophenolate, and belongs to the technical field of fine chemical product synthesis. The synthesis process comprises the following steps of: 1, introducing nitrogen into a reaction kettle, then preheating the reaction kettle to 160-165 DEG C, controlling the pressure to be 0.75-0.8 MPa, adding a quaternary ammonium salt surfactant into p-nitrochlorobenzene, and preheating p-nitrochlorobenzene and a sodium hydroxide solution to 150-155 DEG C; 2, feeding: during feeding, controlling the flow of p-nitrochlorobenzene to be 600-640g/h and the flow of the sodium hydroxide solution to be 5100-5200g/h; and 3, cooling and crystallizing the obtained reaction liquid to obtain sodium p-nitrophenolate. According to the invention, the quaternary ammonium salt surfactant is added in the synthesis of sodium p-nitrophenolate, so that the reaction is milder, the occurrence of side reaction caused by black material formation due to too fast local reaction is prevented to a certain extent, and the yield and the purity are further improved.

Non-heme iron complexes with cis-FeIII(OH)(SAr/OAr) coordination were isolated and examined for their reactivity with a tertiary carbon radical. The sulfur-ligated complex shows a temperature dependence on ?OH versus ArS? transfer, whereas the oxygen-ligated complex does not. These results provide the first working model for C-S bond formation in isopenicillin N synthase and indicate that kinetic control may be a key factor in the selectivity of non-heme iron "rebound"processes.

The reactions of CuCl2·2H2O with chromone thiosemicarbazone ligands containing a-H or-CH3 substituent on terminal N yielded monometallic Cu(ii) complexes [Cu(HL1)Cl2] (1) and [Cu(HL2)Cl2] (2), whereas bimetallic Cu(ii) complexes [Cu(μ-Cl)(HL3)]2Cl2 (3), [Cu(μ-Cl)(HL4)]2Cl2 (4) and [Cu(μ-Cl)(L5)]2 (5) were obtained when a-C2H5,-C6H11 or-C6H5 substituent was present, respectively, in the ligands. The complexes were characterized using elemental analyses, UV-Vis, FT-IR, EPR, mass and TGA studies. The structures of neutral monometallic and dicationic bimetallic complexes were confirmed by single crystal X-ray diffraction, and they exhibited a distorted square pyramidal geometry around Cu(ii) ions. The catecholase-mimicking activity of complexes 1-5 was examined spectrophotometrically, and the results revealed that all the complexes except 5 had the ability to oxidize 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) under aerobic conditions with moderate turnover numbers. In order to find the possible complex-substrate intermediates, a mass spectrometry study was carried out for complexes 1-4 in the presence of 3,5-DTBC. The phosphatase-like activity of 1-5 was also investigated using 4-nitrophenylphosphate (4-NPP) as a model substrate. All the complexes exhibited excellent phosphatase activity in DMF-H2O medium. The complexes displayed significant biomolecular interactions and antioxidant potential. Complex 3 showed good interaction with apoptotic CASP3 protein, VEGFR2 and PIM-1 kinase receptors as revealed by a molecular docking study. Complexes (3-5) exhibited promising cytotoxicity against HeLa-cervical cancer cells with IC50 values of 2.24 (3), 2.25 (4) and 3.77 (5) μM, respectively, and showed a two-fold higher activity than cisplatin. The active complex 3 showed complete inhibition of colony formation at 10 μM concentration. In addition, the acridine orange (AO)/ethidium bromide (EB) staining and real-time live cell imaging results confirmed that complex 3 induced cell death in HeLa cells.

The invention discloses a preparation method of sodium p-nitrophenolate. The preparation method comprises the following steps: a) heating and melting p-chloronitrobenzene in a melting kettle, and preparing a sodium hydroxide solution in a dissolving kettle; b) repeatedly introducing nitrogen into a system 3-6 times to replace air before a reaction, pumping the heated and molten p-chloronitrobenzene and the sodium hydroxide solution into a micro-reactor by using a feeding valve, uniformly mixing, and carrying out a high-temperature and high-pressure reaction; and c) transferring the solution after the reaction to a cooling crystallization kettle, and cooling to separate out a sodium p-nitrophenolate solid containing crystal water. According to the invention, a hydrolysis reaction is carriedout by adopting a micro-channel, so that the instant uniform mixing and the efficient heat transfer of the raw materials are realized while the equivalence ratio of the materials in the reaction process is reduced, the generation of side reactions and the difficulty in post-treatment are reduced, water can be recycled so as to reduce the energy consumption in production, improve the utilization rate of the raw materials and achieve the environment-friendly production process, the production cost is low, and the reaction time is greatly shortened; and the color of the prepared sodium p-nitrophenolate is faint yellow or orange yellow, and by-products are few.

A supramolecular catalytic system for hydrolytic decomposition of toxic phosphorus acid esters has been obtained on the basis of a cationic surfactant with a morpholinium head group and sodium polystyrene sulfonate. Self-organization of the new binary catalytic system has been studied by tensiometry, conductometry, pH-metry, spectrophotometry, and dynamic and electrophoretic light scattering, and its aggregation thresholds have been determined. High solubilizing ability of the system with respect to a hydrophobic guest has been revealed. The morpholinium surfactant has been found to accelerate the hydrolysis of phosphonates up to 50 times in comparison to the reaction in water. The apparent hydrolysis rate constant in the presence of the polyelectrolyte decreases threefold due to reduction of the reactant binding constants.

Covalent B-functionalization of B-doped graphene has been performed for the first time. The electronic properties and Hall effect of functionalized N- and B-doped graphene can be tuned by tailoring the electron-donating/-withdrawing properties of the organic addend.

A supramolecular catalyst of Pd/β-cyclodextrin thin film is synthesized via a facile and one-pot procedure at an oil-water interface. Macrocyclic oligosaccharides of cyclodextrins with glucose units have a wide range of applications due to their hydrophobic and chiral interior. Due to the ability of this supramolecular catalyst to form inclusion complexes with small organic molecules, the as-synthesized catalyst was applied for the reduction of toxic nitroaromatic compounds (p, o, m-nitrophenol and 4-Cl-2-nitrophenol) and the degradation of harmful azo dyes (methyl orange and bismarck brown) with considerable results. This investigation illustrates the change of the catalyst properties in the presence of molecular receptors attached to the catalyst surface.

Supramolecular systems based on a novel tetracationic amphiphilic multiheterocycle have been studied by tensiometry, conductometry, pH-metry, spectrophotometry, and dynamic and electrophoretic light scattering. The critical micelle concentration of the system has been determined (0.4 mM), and the possibility of open and closed association models realization has been demonstrated. A high solubilizing ability of the aggregates toward hydrophobic guest species has been revealed. Micellar catalysts based on the new multiheterocycle have shown substrate specificity in the hydrolysis of phosphonates possessing different hydrophobicities.

The 4H+/4e- reduction of O2 to water, a key fuelcell reaction also carried out in biology by oxidase enzymes, includes the critical O-O bond reductive cleavage step. Mechanistic investigations on active-site model compounds, which are synthesized by rational design to incorporate systematic variations, can focus on and resolve answers to fundamental questions, including protonation and/or H-bonding aspects, which accompany electron transfer. Here, we describe the nature and comparative reactivity of two low-spin heme-peroxo-Cu complexes, LS-4DCHIm, [(DCHIm)F8FeIII-(O2 2-)-CuII(DCHIm)4]+, and LS-3DCHIm, [(DCHIm)F8FeIII-(O2 2-)-CuII(DCHIm)3]+ (F8 = tetrakis(2,6-difluorophenyl)-porphyrinate; DCHIm = 1,5-dicyclohexylimidazole), toward different proton (4-nitrophenol and [DMF·H+](CF3SO3 -)) (DMF = dimethylformamide) or electron (decamethylferrocene (Fc?)) sources. Spectroscopic reactivity studies show that differences in structure and electronic properties of LS-3DCHIm and LS-4DCHIm lead to significant differences in behavior. LS-3DCHIm is resistant to reduction, is unreactive toward weakly acidic 4-NO2-phenol, and stronger acids cleave the metal-O bonds, releasing H2O2. By contrast, LS-4DCHIm forms an adduct with 4-NO2-phenol, which includes an H-bond to the peroxo O-atom distal to Fe (resonance Raman (rR) spectroscopy and DFT). With addition of Fc?(2 equiv overall required), O-O reductive cleavage occurs, giving water, Fe(III), and Cu(II) products; however, a kinetic study reveals a one-electron rate-determining process, ket = 1.6 M-1 s-1 (-90 °C). The intermediacy of a high-valent [(DCHIm)F8FeIV=O] species is thus implied, and separate experiments show that one-electron reduction-protonation of [(DCHIm)F8FeIV=O] occurs faster (ket2 = 5.0 M-1 s-1), consistent with the overall postulated mechanism. The importance of the H-bonding interaction as a prerequisite for reductive cleavage is highlighted.

Organic-inorganic hybrid nano-building blocks of aromatic nitro-, aldehyde-, and bromo-functionalized polyhedral oligomeric silsesquioxanes were easily prepared through nucleophilic substitutions, starting from the reactions between octakis(3-chloropropyl)octasilsesquioxane and phenoxide derivatives. These phenoxide anions not only supply the substitution functions to a silsesquioxane cage, but can also induce a cage-rearrangement leading to the formation of octa-, deca-, and dodecahedral silsesquioxane cages. This journal is

Innovative in situ characterization tools are essential for understanding the reaction mechanisms leading to the growth of nanoscale materials. Though techniques, such as in situ transmission X-ray microscopy, fast single-particle spectroscopy, small-angle X-ray scattering, etc., are currently being developed, these tools are complex, not easily accessible, and do not necessarily provide the temporal resolution required to follow the formation of nanomaterials in real time. Here, we demonstrate for the first time the utility of a simple millifluidic chip for an in situ real time analysis of morphology and dimension-controlled growth of gold nano- and microstructures with a time resolution of 5 ms. The structures formed were characterized using synchrotron radiation-based in situ X-ray absorption spectroscopy, 3-D X-ray tomography, and high-resolution electron microscopy. These gold nanostructures were found to be catalytically active for conversion of 4-nitrophenol into 4-aminophenol, providing an example of the potential opportunities for time-resolved analysis of catalytic reactions. While the investigations reported here are focused on gold nanostructures, the technique can be applied to analyze the time-resolved growth of other types of nanostructured metals and metal oxides. With the ability to probe at least a 10-fold higher concentrations, in comparison with traditional microfluidics, the tool has potential to revolutionize a broad range of fields from catalysis, molecular analysis, biodefense, and molecular biology.

Three new metal-coordinating ligands, L1·4HCl [1-(2-guanidinoethyl)-1,4,7-triazacyclononane tetrahydrochloride], L 2·4HCl [1-(3-guanidinopropyl)-1,4,7-triazacyclononane tetrahydrochloride], and L3·4HCl [1-(4-guanidinobutyl)-1,4,7- triazacyclononane tetrahydrochloride], have been prepared via the selective N-functionalization of 1,4,7-triazacyclononane (tacn) with ethylguanidine, propylguanidine, and butylguanidine pendants, respectively. Reaction of L 1·4HCl with Cu(ClO4)2·6H 2O in basic aqueous solution led to the crystallization of a monohydroxo-bridged binuclear copper(II) complex, [Cu2L 12(μ-OH)](ClO4)3·H 2O (C1), while for L2 and L3, mononuclear complexes of composition [Cu(L2H)Cl2]Cl· (MeOH)0.5· (H2O)0.5 (C2) and [Cu(L 3H)Cl2]Cl· (DMF)0.5· (H 2O)0.5 (C3) were crystallized from methanol and DMF solutions, respectively. X-ray crystallography revealed that in addition to a tacn ring from L1 ligand, each copper(II) center in C1 is coordinated to a neutral guanidine pendant. In contrast, the guanidinium pendants in C2 and C3 are protonated and extend away from the Cu(II)-tacn units. Complex C1 features a single μ-hydroxo bridge between the two copper(II) centers, which mediates strong antiferromagnetic coupling between the metal centers. Complexes C2 and C3 cleave two model phosphodiesters, bis(p-nitrophenyl)phosphate (BNPP) and 2-hydroxypropyl-p-nitrophenylphosphate (HPNPP), more rapidly than C1, which displays similar reactivity to [Cu(tacn)(OH2)2] 2+. All three complexes cleave supercoiled plasmid DNA (pBR 322) at significantly faster rates than the corresponding bis(alkylguanidine) complexes and [Cu(tacn)(OH2)2]2+. The high DNA cleavage rate for C1 {kobs = 1.30 (±0.01) × 10-4 s-1 vs 1.23 (±0.37) × 10-5 s-1 for [Cu(tacn)(OH2)2]2+ and 1.58 (±0.05) × 10-5 s-1 for the corresponding bis(ethylguanidine) analogue} indicates that the coordinated guanidine group in C1 may be displaced to allow for substrate binding/activation. Comparison of the phosphate ester cleavage properties of complexes C1-C3 with those of related complexes suggests some degree of cooperativity between the Cu(II) centers and the guanidinium groups.

Gold nanoparticles (AuNP) supported on hydrotalcite, γ-Al 2O3 and TiO2 P25 have been prepared photochemically under mild conditions using ketyl radicals as the primary reducing agent; these nanocomposites were prepared directly in the solid phase. Such dry, solventless methods are attractive from an environmental perspective. The composite materials were successfully characterized using diffuse reflectance UV-visible spectroscopy, SEM, TEM, X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The supported AuNP were predominantly spherical and ranged in size from 20-140 nm depending on the support and the percent Au loading, indicating the potential applications of these particles as photocatalysts. The catalytic activity of the supported AuNP was evaluated using the well-studied reduction of 4-nitrophenol. UV-visible spectroscopy was used to monitor the reaction and illustrated the ability of these easily prepared AuNP composites to act has heterogeneous catalysts. The role of percent Au loading and type of support on the catalytic activity of supported AuNP was also investigated. Composites with relatively large AuNP may hold promise as efficient catalysts in plasmon-mediated light-driven reactions.

The micellization properties, solubilization capability, and catalytic effect of conventional nonionic surfactants and amphiphilic compounds of oligomeric (Tyloxapol) and polymeric (Synperonic F-68, Pluronic F-127) structure were compared. The systems studied demonstrate a marked catalytic effect toward basic hydrolysis of p-nitrophenyl laurate, which exceeds the effect of aqueous alkali solutions by two orders of magnitude. Correlations between the solubilization capacity of aggregates and their catalytic effect were observed. The maximum efficiency was found for the Tyloxapol solution. The synergetic enhancement of the catalytic effect was observed for the mixed Tyloxapol-cetyltrimethylammonium bromide systems in the presence of small amounts of cationic surfactant

Second-order rate constants (kOH-) have been measured spectrophotometrically for alkaline hydrolysis of Y-substituted phenyl phenyl carbonates (2a-j) and compared with the kOH- values reported previously for the corresponding reactions of Y-substituted phenyl benzoates (1a-j). Carbonates 2a-j are 8 ～ 16 times more reactive than benzoates 1a-j. The Hammett plots correlated with σ- and σo constants exhibit many scattered points, while the Yukawa-Tsuno plot results in excellent linear correlation with ρ = 1.21 and r = 0.33. Thus, the reaction has been concluded to proceed through a concerted mechanism in which expulsion of the leaving group is advanced only a little. However, one cannot exclude a possibility that the current reaction proceeds through a forced concerted mechanism with a highly unstable intermediate.

(Figure Presented) The need to have a measure of the strength of some substituted benzoic acids in ionic liquid solution led us to use the protonation equilibrium of sodium p-nitrophenolate as a probe reaction, which was studied by means of spectrophotometric titration at 298 K. In order to evaluate the importance of electronic effect of the substituents present on the aromatic ring, both electron-withdrawing and -donor substituents were taken into account. Furthermore, to have a measure of the importance of the steric effect of the substituents both para- and ortho-substituted benzoic acids were analyzed. The probe reaction was studied in two ionic liquids differing for the ability of the cation to give hydrogen bond and π-π interactions, namely [bm 2im][NTf2] and [bmpyrr][NTf2]. Data collected show that benzoic acids are less dissociated in ionic liquid than in water solution. Furthermore, the equilibrium constant values seem to be significantly affected by both the nature of ionic liquid cation and the structure of the acid. In particular, the ortho-steric effect seems to operate differently in water and in the aromatic ionic liquid, determining in this solvent medium a particular behavior for ortho-substituted benzoic acids.

Resorcinarene-functionalized gold nanoparticles (AuNPs) were prepared conveniently in aqueous solution in the presence of amphiphilic tetramethoxyresorcinarene tetraaminoamide. The obtained AuNPs were characterized and analyzed by UV-vis, FT-IR, XRD and TEM, respectively. The results showed that the size of AuNPs and the standard deviations were all decreasing with the increase of resorcinarene concentration. In addition, the catalytic activity of the obtained AuNPs in the reduction of aromatic nitro compounds was also investigated. In aqueous solution the reaction follows a first order kinetics and the size of AuNPs has influence on the rate of reduction.

Metal nanoparticle-chitosan (NPs-chitosan) bioconjugates were formed by exposure of chitosan to an aqueous solution of metal salts under thermal treatment. The metal nanoparticles that are formed strongly bound to chitosan, which encouraged us to investigate their catalytic performance. It was demonstrated that the metal NPs-chitosan bioconjugates functioned as effective catalysts for the reduction of 4-nitrophenol in the presence of NaBH4, which was monitored by means of spectrophotometry as a function of reaction time. The silver NPs-chitosan bioconjugates exhibited excellent catalytic activity and were reusable for up to seven cycles. In contrast, the gold NPs-chitosan catalyst displayed poor catalytic activity, even in the second cycle. A highlight of our approach is that chitosan simultaneously acts as an active support for the synthesis and assembly of nanoparticles, and the resultant bioconjugates bear the advantage of easy separation from the reaction medium.

Hexakis(3-0-methyl)-α,-cyclodextrin (3α) bound tom-and p-nitrophenolate ions more strongly, whereas hexakis(2-0-methy1)-α- cyclodextrin (2α) bound less strongly than native α-cyclodextrin. ROESY spectra showed that the 3-0-mefhyl groups of 3a interact with the guest protons, whereas 2-0-methyl groups of 2a do not. 3a accelerated and 2a decelerated the cleavage of m-nitrophenyl acetate in an alkaline solution, suggesting that the C(2)-OH of α-cyclodextrin is more catalytic than the C(3)-OH. However, the catalytic effect of 3a was much smaller than that of native a-cyclodextrin. Loss of hydrogen bonding between the C(3)-OH and C(2)-OH by 3-O-permethylation is responsible for the small catalytic effects of 3α. Similar results were obtained for β-cyclodextrin analogs.

(Chemical Equation Presented) N-Heterocyclic carbenes (NHCs) catalyze a new Mannich-type reaction to form β-amino acid derivatives in high yield and enantioselectivity. The reaction is initiated by the addition of an NHC to an C-aryloxyaldehyde followed by elimination of a phenoxide anion which generates an enol/enolate. A Mannich addition to a tosylimine proceeds with excellent control over enantioselectivity. In a new carbene catalysis concept, catalyst regeneration is promoted by return, or rebound, and acylation of the phenoxide group which served as the activating component in the first step of the catalytic cycle. The activated ester products formed in situ are manipulated to form a variety of useful compounds including β-amino acids, β-amino amides, and peptides.

The reaction catalyzed by the protein phosphatase-1 (PP1) has been examined by linear free energy relationships and kinetic isotope effects. With the substrate 4-nitrophenyl phosphate (4NPP), the reaction exhibits a bell-shaped pH-rate profile for kcat/KM indicative of catalysis by both acidic and basic residues, with kinetic pKa values of 6.0 and 7.2. The enzymatic hydrolysis of a series of aryl monoester substrates yields a Bronsted βlg of -0.32, considerably less negative than that of the uncatalyzed hydrolysis of monoester dianions (-1.23). Kinetic isotope effects in the leaving group with the substrate 4NPP are 18(V/K)bridge = 1.0170 and 15(V/K) = 1.0010, which, compared against other enzymatic KIEs with and without general acid catalysis, are consistent with a loose transition state with partial neutralization of the leaving group. PP1 also efficiently catalyzes the hydrolysis of 4-nitrophenyl methylphosphonate (4NPMP). The enzymatic hydrolysis of a series of aryl methylphosphonate substrates yields a Bronsted βlg of -0.30, smaller than the alkaline hydrolysis (-0.69) and similar to the βlg measured for monoester substrates, indicative of similar transition states. The KIEs and the βlg data point to a transition state for the alkaline hydrolysis of 4NPMP that is similar to that of diesters with the same leaving group. For the enzymatic reaction of 4NPMP, the KIEs are indicative of a transition state that is somewhat looser than the alkaline hydrolysis reaction and similar to the PP1-catalyzed monoester reaction. The data cumulatively point to enzymatic transition states for aryl phosphate monoester and aryl methylphosphonate hydrolysis reactions that are much more similar to one another than the nonenzymatic hydrolysis reactions of the two substrates.

In a study of the origin of the α-effect and its dependence on the nature of the reaction medium as well as structural effects, we report herein a kinetic study of the reactions of p-nitrophenyl benzoate (PNPB) with butan-2,3-dione monoximate (Ox-, α-nucleophile) and p-chlorophenoxide (p-ClPhO-, the reference nucleophile) in dimethyl sulfoxide (DMSO)-H2O mixtures of varying compositions at 25.0 ± 0.1°C. The second-order rate constants (kN) decrease modestly on addition of DMSO to the medium up to 10 mol% DMSO but increase significantly beyond that point for both nucleophiles. Ox- is more reactive than p-ClPhO- in all solvent mixtures studied (i.e., the α-effect). The α-effect increases as the DMSO content in the medium increases up to 40 mol% DMSO and then decreases beyond that point resulting in a bell-shaped α-effect profile. The bell-shaped α-effect profile obtained for the current reaction is similar to that found previously for the corresponding reaction of p-nitrophenyl acetate (PNPA), differing notably however, in the magnitude of the α-effect beyond 40 mol% DMSO. The PNPB/p-ClPhO- reaction gains greater rate enhancement than the PNPA/p-ClPhO- reaction in the DMSO-rich region, resulting in the smaller α-effect for PNPB beyond 40 mol% DMSO. It is proposed that the observed modulation of the α-effect by the solvent medium is explicable as a ground-state effect in the H2O-rich region and a transition-state effect in the DMSO-rich region.

For a simple biphasic hydrolysis, we show that the application of various reaction conditions in microreactors using segmented flow can dramatically increase the reaction rate. A tandem diazotation/ Heck reaction served as an example that even homogeneous reactions can be accelerated by segmentation in microreactors.

We report on a nucleophilic study of esters R-C(=X)-Y-Ar in which the electrophilic center has been modified by replacing O by S in the leaving group or carbonyl center: 4-nitrophenyl acetate (1), S-4-nitrophenyl thioacetate (2), 4-nitrophenyl benzoate (3), and O-4-nitrophenyl thionobenzoate (4). The studies include O- and S- nucleophiles as well as α nucleophiles in H2O at 25.0 ± 0.1°C. The sulfur nucleophile (4-chlorothiophenoxide, 4-ClPhS-) exhibits significant enhanced reactivity for the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. On the contrary, the common nucleophile OH- is much less reactive towards 2 and 4 compared with 1 and 3. The effect of changing both the electrophilic center and the nucleofugic center on the reactivity of the other oxygen nucleophiles is not so significant: 4-chlorophenoxide (4-ClPhO-) is four to six times more reactive in the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. The α effects exhibited by butan-2,3-dione monoximate (Ox-) and HOO- are strongly dependent on the nature of the electrophilic center of the substrates, indicating that the difference in the ground-state solvation energy cannot be fully responsible for the α effect. Our results clearly emphasize the strong dependence of the α effect on the substrate structure, notably, the nature of the electrophilic center. The impact of change in the nucleofuge (1-→2) and the electrophilic center (3-→4) on reactivity indicates that anucleophiles will need to be "purpose built" for decontamination and nucleophilic degradation of specific biocides.

The invention relates to a method of preparing a high-purity nitrophenol and, more specifically, p-nitrophenol from a nitrohalobenzene. The inventive method comprises the following steps: (a) hydrolysis of a nitrohalobenzene compound by reacting said compound with a base; (b) acidification in order to produce the nitrophenol compound from the salt thereof by means of an acid treatment; (c) crystallisation of the nitrophenol compound obtained; and (d) separation of the product obtained. The invention is characterised in that it also comprises at least the following steps: (e) concentration of the reaction medium after hydrolysis (a) and before acidification (b); and (f) liquid/liquid decantation after acidification (b) and before crystallisation (c), which is intended to eliminate the water phase obtained after acidification (b).

Provided are methods for synthesizing radiotracers, including no carrier added (n.c.a.) tracers suitable as PET scan tracers that contain a 18F—P bond. The radiolabeled products may be synthesized from precursors including phosphorus(V) and/or phosphorus (III) atoms bound to a suitable leaving group or group(s). For example, precursors incorporating a nitrophenoxy leaving group bound to a phosphorus(V) atom tend to exhibit an acceptable combination of stability and reactivity and also tend to allow the precursor compound(s) to be separated more easily from the 18F-labeled products. The methods disclosed herein for producing radiolabeled compounds incorporating a P—18F chemistry may particularly useful radiolabeling oligonucleotides, phospholipids, phosphorilated proteins, sugars and steroids for use as PET radiotracer compounds for medical imaging applications.

The present invention provides 4-hydroxyquinoline-3-carboxamide and hydrazide compounds of formula I These compounds are useful to treat or prevent the herpesviral infections, particularly, human cytomegaloviral infection.

Nearly all of the reported studies of reactions of sulfate diesters are for dialkyl or alkyl aryl diesters, which undergo reaction by carbon-oxygen bond fission. Sulfuryl transfer reactions of sulfate diesters (RO-SO 2-OR′) proceeding by attack at sulfur have been little explored. When both ester groups are aryl groups the hydrolysis reaction (sulfuryl transfer to water) occurs by way of attack at sulfur. The alkaline hydrolysis of diaryl sulfate diesters was shown to obey first-order kinetics with respect to [-OH] and proceed through S-O bond fission, in a mechanism that is most likely concerted. Activation parameters for 4-chloro-3-nitrophenyl phenyl sulfate and 4-nitrophenyl phenyl sulfate gave the following respective values: ΔH? = 88.0 ± 0.1 and 84.83 ± 0.06 kJ mol-1 and ΔS? = -37 ± 1 and -50.2 ± 0.5 J mol-1 deg-1. The dependence of the second-order rate constant for hydrolysis on leaving group pKa was analyzed giving a β1g slope of -0.7 ± 0.2 and a Leffler α parameter value of 0.36. A 15k kinetic isotope effect (KIE) for the hydroxide attack on 4-nitrophenyl phenyl sulfate of 1.0000 ±0.0005 and an 18k1g KIE value of 1.003±0.002 were obtained.

The effect of electrostatic interactions on the transition-state character for enzymatic phosphoryl transfer has been a subject of much debate. In this work, we investigate the transition state for alkaline phosphatase (AP) using linear free-energy relationships (LFERs). We determined fcat/K M for a series of aryl sulfate ester monoanions to obtain the Bronsted coefficient, βIg, and compared the value to that obtained previously for a series of aryl phosphorothioate ester dianion substrates. Despite the difference in substrate charge, the observed Bronsted coefficients for AP-catalyzed aryl sulfate and aryl phosphorothioate hydrolysis (-0.76 ± 0.14 and -0.77 ± 0.10, respectively) are strikingly similar, with steric effects being responsible for the uncertainties in these values. Aryl sulfates and aryl phosphates react via similar loose transition states in solution. These observations suggest an apparent equivalency of the transition states for phosphorothioate and sulfate hydrolysis reactions at the AP active site and, thus, negligible effects of active site electrostatic interactions on charge distribution in the transition state.

A process for the preparation of 5-[[4-[2-(5-ethyl-2-pyridinyl)ethoxy]phenyl]methyl]-2,4-thiazolidinedione (formula 1) comprising a. reacting diazonium salt of 4-[2-(5-Ethyl-2-pyridyl) ethoxy] amino- benzene, compound of formula 2, with acrylamide, aqueous HX (wherein X is Br or Cl), under meerwein arylation conditions to yield compound of formula 3; b. condensing compound of formula 3 with thiourea to obtain compound of formula 4; and c. converting compound of formula 4 to compound of formula 1.

In the reaction of paraoxon with alkali metal ethoxides, ion-paired EtO-M+ species are more reactive than the dissociated EtO- with the reactivity order EtO-Li+ EtO-Na+ > EtO-K+ > EtO-, while in the reaction of parathion, the reactivity follows the order

In continuation of our studies of alkali metal ion catalysis and inhibition at carbon, phosphorus, and sulfur centers, the role of alkali metal ions in nucleophilic displacement reactions of p-nitrophenyl phenylphosphonate (PNPP) has been examined. All al

Use of commercial perpropionic acid (PPA), the first stable, industrial and water-miscible peroxyacid, allows the destruction of toxic organophosphorus and organosulfur compounds under micellar conditions. The destruction of paraoxon (O,O-diethyl O-p-nitrophenylphosphate), di-n-butyl sulfide and 2-chloro-2′-phenyldiethyl sulfide has been studied.

The kinetics of the hydrolysis of 4-nitrophenyl glycine ester (PNPG) catalysed by [Co(OH)(trien)(OH2)]2+, [Co(OH)(tren)(OH2)]2+ and [Co(OH)(en)2(OH2)]2+ complexes has been studied spectrophotometrically in weakly basic aqueous media (pH = 6.5 to 7.4). Kinetic experiments were carried out as a function of the pH, complex concentration and temperature. The rate of hydrolysis increases linearly with the complex concentration with a trend to wards rate saturation, suggesting the formation of associative species in a pre-equilibrium step. The pseudo-first order rate constant, kobs, increases rapidly with a decrease in the hydrogen-ion concentration. The complexes promote the hydrolysis of 4-nitrophenyl glycinate significantly, and the acceleration rate is about 400-600. An attack of external OH- on the chelated ester is suggested as a probable mechanism for the hydrolysis. The lower rate enhancements observed in the present study could probably be ascribed to a weaker cobalt(III) alkoxy carbonyl interaction in the chelate, owing to a decreased nucleophilicity of the carbonyl oxygen in the p-nitrophenyl ester. The activation parameters for all three complex-promoted reactions are found to be comparable, thus suggesting a common mechanism operative in all complex catalysed reactions.

Chemical decontamination of toxic compounds (chemical warfare agents and/or insecticides) is of increasing importance. In this study, we report the use of ω-phthalimidoperoxyalkanoic acids 2 in the destruction of paraoxon (O,O-diethyl-O-para-nitrophenylphosphate), a well-known insecticide, and 2-chloro-2′-phenyldiethyl sulfide (a half mustard). We show that while all the peroxyacids used in this series allow the destruction of toxic compounds, the length n of the alkanoic side chain is important to the choice of the optimal industrial compound, which is 2d (n = 5).

New initiators 1-7, analogues of tetra-acetylethylenediamine, have been prepared and their use in the in situ generation of peroxyacids by reaction with sodium peroxycarbonate described. The kinetics of perhydrolysis of these initiators in aqueous solutio

The nickel(II) complexes, [(tpa)Ni(II)(μ-OH)2Ni(II)(tpa)](ClO4)2 (tpa = tris(2-pyridylmethyl)amine) (2), [Ni(II)(CH3CN)(tpa)(H2O)](ClO4)2 (3) have been prepared and fully characterized. X-Ray crystallography of complex 2 and its methanol adduct, [(tpa)Ni(II)(μ- OH)2Ni(II)(tpa)](ClO4)2·2MeOH ((2)·2MeOH) revealed a molecular structure containing two Ni centers bridged by two OH ligands. The Ni-O distances in 2·2MeOH are longer than those in 2. The MeCN ligand in complex 3 is replaced by EtCN to give [Ni(II)(EtCN)(tpa)(H2O)](ClO4)2 (4), which was characterized by X-ray crystallography. The kinetic study of p-NPA (p- nitrophenyl acetate, 0.1, 0.5, 1 mM) hydrolysis by complex 2 (20, 10, 6 mM) was performed in the presence of ethanol (100 mM) in MeCN solution (1 M = 1 mol dm-3). By following the 400 nm absorption derived from p-nitrophenolate ion, we obtained the second-order kinetics; first-order in [2] and first- order in [p-NPA]. Addition of ethanol resulted in enhancement of the second- order rate constant (from 1.6x10-3 M-1 s-1 to 1.6x10-2 M-1 s-1 at 25°C) as well as formation of a transesterified product, ethyl acetate. The second-order rate constant of the reaction in the presence of added ethanol (0.016 M-1 s-1) at 25°C is much larger than that of the reaction without ethanol (0.0016 M-1 s-1). Also observed was a transesterified product, ethyl acetate, from the reaction of 2 with p-NPA in the presence of ethanol. The pK(a) value of the ligated water molecule in 3 was estimated to be 10.7 by kinetic measurements in 40% MeCN aqueous solution at 25°C, I = 0.3.

Reactions of OH- and F- with p-nitrophenyl diphenyl phosphate (pNPDPP) are inhibited by very dilute dodecyl (10) and (23) polyoxyethylene glycol (C12E10 and C12E23, respectively), but rate constants become independent of surfactant concentrations at concentrations above the critical micelle concentration. Low charge density anions, e.g., ClO4-, inhibit and low charge density cations, e.g., (n-C7H15)4N+, accelerate reactions, probably by controlling concentrations of nucleophiles in the palisade layer. Diphenyl phosphorofluoridate, generated by attack of F-, is not detected but is rapidly hydrolyzed to phenyl phosphorofluoridate or diphenyl phosphate ion with loss of phenol or F-. The products are different in DMSO containing modest amounts (- on the initial phosphorofluoridate. These differences are consistent with the micellar palisade layer being water-rich. Although the nonionic surfactants do not intervene nucleophilically in reactions of pNPDPP, considerable amounts of ether are formed in the reaction of 2,4-dinitrochlorobenzene (DNCB), in C12E10 and C12E23 at high pH by attack of alkoxide ion with the relatively hydrophilic DNCB located close to the micellar surface. The differences in the chemistries of reactions of pNPDPP and DNCB appear to be associated largely with differences in locations of these substrates in the nonionic micelles.

Hydrlysis of aryl carbazates (H2NNHCO2Ar with Ar=phenyl, 3- or 4-chlorophenyl, 3- or 4-nitrophenyl, 4-methylphenyl and 4-methoxyphenyl) and/or their 2- or 3-methyl derivatives in aqueous buffers or sodium hydroxide solutions gives phenolate and sodium carbazate. the kinetics and acidity constants and thermodynamic parameters are given.By analysing the pH profiles, the activation entropy, and effects of the substituent on the aromatic ring it was found that aryl carbazates containing a methyl group in the 2 position are hydrolysed by a BAc2 mechanism and the others by an E2cB mechanism.The pH profiles of nitrophenyl carbazates show a maximum.The rate of decarboxylation of carbazic acid decreases with increasing pH value.

Cetyltrimethylammonium hydroperoxide solutions are easily prepared by mixing cetyltrimethylammonium hydroxide and hydrogen peroxide and are very efficient in promoting paraoxon (diethyl p-nitrophenyl phosphate) hydrolysis.

Second-order rate constants of reactions of HO- with phosphate, phosphinate and thiophosphinate esters, (PhO)2PO.OC6H4NO2-p, Ph2PO.OC6H4NO2-p, Ph2PO.SPh, Ph2PO.SC6H4NO2-p and Ph2PO.SEt, go through minima with decreasing water content of H2O-MeCN or H2O-t-BuOH. The rate decrease is due to stabilization of the non-ionic ester on addition of organic solvent to H2O. This inhibition is partially offset by stabilization of the anionic transition states and in the drier solvents partial desolvation of HO- increases rates.

Specific salting-in effects that lead to striking substrate selectivity were observed for the hydrolysis of p-nitrophenyl alkanoates 2 (n = 2-16) catalyzed by 4-(dialkylamino)pyridine-functionalized polymer 1 in aqueous Tris buffer solution at pH 8.0 and 30°C. Macromolecule 1 was found to exhibit clear substrate preference for 2 (n = 6) in 0.05 M aqueous Tris buffer solution, as contrasted with the corresponding reaction in 0.05 M aqueous phosphate or borate buffer solutions where the substrate selectivity is absent. The formation of a reactive catalyst substrate complex, 1·2, appears to be promoted by the presence of tris(hydroxymethyl)methylammonium ion, an efficient salting-in agent, from the Tris buffer system. The salting-in effect on formation of 1·2 complex is presumed responsible for the substrate specificity. The salting-out effects of sodium chloride on the solvolysis of 2 catalyzed by 1 were also investigated in 1:1 (v/v) methanol-water solution at pH 8.0 and 30°C. The rate of 1-catalyzed solvolysis of 2 (n = 10-16) was found to vary inversely with NaCl concentration (0-1.0 M). The magnitude of the salting-out effects is dependent on the alkyl chain length in 2 and the concentrations of 1 and NaCl. At 7.5 x 10-5 unit mol L-1 1 and 0-1.0 M NaCl the order of reactivity for 2 (n = 10-16) was n = 10 > 12 > 14 > 16. However, at 5.0 x 10-6 unit mol L-1 1, a revised reactivity order, 2, n = 14 > 12 > 16, was obtained at [NaCl] 0.15 M. A significant decrease in the substrate preference for 1-catalyzed solvolysis of 2 (n = 10-16) was observed at higher NaCl concentrations. We suggest that the reduced catalytic efficiency and selectivity expressed by 1 in the presence of sodium chloride should be attributed to changes in the morphology and composition of aggregates containing 1 and 2 in aqueous methanol solution that lead to decreased dependence of aggregate formation on the hydrophobicity of the substrate.