4-fluorobenzoic Acid Research Articles

Influence of noncovalent intermolecular interactions on crystal packing: syntheses and crystal structures of three layered Zn(ii)/1,2,4-triazole/carboxylate coordination polymers

Three 2D layered zinc coordination polymers: Zn(trz)(HBDC) (1), Zn4(trz)4(4-FBA)4·(H2O)0.5 (2) and Zn4(trz)4(4-CBA)4 (3) (trz = 1,2,4-triazole, H2BDC = 1,3-benzenedicarboxylic acid, 4-HFBA = 4-fluorobenzoic acid and 4-HCBA = 4-chlorobenzoic acid) have been synthesized by hydrothermal reactions and characterized by IR, elemental analysis, TGA measurements and X-ray single-crystal analysis. Compounds 1–3 have the same 2D layer constructed by zinc(II) with trz and carboxylate. The main difference in the structure of the three compounds is the interactions between the layers. Compound 1 shows unusual intermolecular hydrogen bonding and C–O⋯π interactions, compound 2 exhibits intermolecular hydrogen bonding and C–F⋯π interactions, while compound 3 only shows intermolecular C–Cl⋯π interactions. It is found that the noncovalent intermolecular interactions have an influence on crystal packing.

Antituberculosis activity of hydrazones derived from 4-fluorobenzoic acid hydrazide

A series of substitututed methylene/ethylene 4-fluorophenylhydrazide derivatives (3a–p) was synthesized with the aim of evaluating their antimycobacterial activity toward a strain of Mycobacterium tuberculosis H37Rv. Their chemical structures were confirmed by 1H-nuclear magnetic resonance (NMR) and electrospray mass spectrometry (ES-MS) spectral data, and elemental analysis. The in vitro antimycobacterial evaluation was performed according to the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) antituberculosis drug discovery program. Compound 3a, 4-fluorobenzoic acid [(2,6-dichlorophenyl) methylene]hydrazide, showed the highest inhibitory activity of all the compounds under study.

Synthesis and Crystal Structure of Complex [Nd(2-FC6H4COO)3·(2-FC6H4COOH)·H2O

The neodymium complex with 2-fluorobenzoic acid was synthesized and characterized by X-ray diffraction. The complex crystallizes in the triclinic system with space group Pī, lattice parameters: a = 9.2747(10) A, b = 11.7594(13) A, c = 13.5158(14) A, α = 110.220(2)°, β = 93.930(2)°, γ = 90.894(2)°, V = 1378.8(3) A3, Z = 1, Dcalc = 1.733 Mg/m3. The complex is a binuclear molecule in which four 2-fluorobenzoato groups act as bidentate and tridentate bridges between the two Nd3+ ions. Each Nd3+ ion is additionally chelated by one 2-fluorobenzoato group and coordinated by one 2-fluorobenzoic acid and one water molecule.

A selective 19F NMR spectroscopic method for determination of insecticide diflubenzuron in different media

A selective and rapid 19F NMR spectroscopic analytical procedure for insect growth regulator diflubenzuron, a phenylurea insecticide, has been developed. Optimal NMR sensitivity based upon T 1 relaxation time was investigated for diflubenzuron and 4-fluorobenzoic acid as internal standard in dimethyl sulphoxide. The method was validated through spike and recovery for diflubenzuron from apple juice and its commercial sample (Dimilin) without any interference, separation steps and lengthy instrument time. The calibration curve was linear for diflubenzuron over the range of 25–1000 μg/ml, with detection limit (S/N = 3) of 6 μg/ml. The within- and between-day repeatability coefficients of variation were lower than 6 ( n = 3) and 7 ( n = 5), respectively. Recovery of diflubenzuron from spiked apple juice samples at two fortification levels were 96% and 92% with relative standard deviation of <10% ( n = 3).

Synthesis, structure and luminescence properties of two novel lanthanide complexes with 2-fluorobenzoic acid and 1,10-phenanthroline

Two lanthanide complexes with 2-fluorobenzoate (2-FBA) and 1,10-phenanthroline (phen) were synthesized and characterized by X-ray diffraction. The structure of each complex contains two non-equivalent binuclear molecules, [Ln(2-FBA)3 · phen · CH3CH2OH]2 and [Ln(2-FBA)3 · phen]2 (Ln = Eu (1) and Sm (2)). In [Ln(2-FBA)3 · phen · CH3CH2OH]2, the Ln3+ is surrounded by eight atoms, five O atoms from five 2-FBA groups, one O atom from ethanol and two N atoms from phen ligand; 2-FBA groups coordinate Ln3+ with monodentate and bridging coordination modes. The polyhedron around Ln3+ is a distorted square-antiprism. In [Ln(2-FBA)3 · phen]2, the Ln3+ is coordinated by nine atoms, seven O atoms from five 2-FBA groups and two N atoms of phen ligand; 2-FBA groups coordinate Ln3+ ion with chelating, bridging and chelating-bridging three coordination modes. The polyhedron around Ln3+ ion is a distorted, monocapped square-antiprism. The europium complex exhibits strong red fluorescence from 5D0 → 7F j ( j = 1–4) transition emission of Eu3+.

Crystal structure of (2,2′-bipyridine-N,N′)bis(2-fluorobenzoato)lead(II), Pb(C7H4O2F)2(C10H8N2)

Abstract C24H16F2N2O4Pb, triclinic, P1̅ (no. 2), a = 9.494(2) Å, b = 10.231(2) Å, c = 11.996(2) Å, α = 82.84(3)°, β = 85.53(3)°, γ = 70.25(3)°, V = 1087.3 Å3, Z = 2, Rgt(F) = 0.027, wRref(F2) = 0.063, T = 293 K.

Synthesis and characterization of novel hydrazide–hydrazones and the study of their structure–antituberculosis activity

A series of hydrazide–hydrazones, based on a series of 4-substituted benzoic acid, were synthesized, and their structures were elucidated and screened for the antituberculosis activity against Mycobacterium tuberculosis H37Rv with the help of the BACTEC 460 radiometric system. Compound 3, 4-fluorobenzoic acid [((5-nitro)thiophen-2yl) methylene]hydrazide showed the highest inhibitory activity in this series. The search of pharmacophores was done by means of the Electronic-Topological Method (ETM). The model developed in this study is supposed to be applied to the design, preparation and screening of new compounds of similar structure in order to further test and optimize the model with the eventual goal of preparing new anti-tubercular agents.

Acidity of Frozen Electrolyte Solutions

Ice is selectively intolerant to impurities. A preponderance of implanted anions or cations generates electrical imbalances in ice grown from electrolyte solutions. Since the excess charges are ultimately neutralized via interfacial (H(+)/HO(-)) transport, the acidity of the unfrozen portion can change significantly and permanently. This insufficiently recognized phenomenon should critically affect rates and equilibria in frozen media. Here we report the effective (19)F NMR chemical shift of 3-fluorobenzoic acid as in situ probe of the acidity of extensively frozen electrolyte solutions. The sign and magnitude of the acidity changes associated with freezing are largely determined by specific ion combinations, but depend also on solute concentration and/or the extent of supercooling. NaCl solutions become more basic, those of (NH(4))(2)SO(4) or Na(2)SO(4) become more acidic, while solutions of the 2-(N-morpholino)ethanesulfonic acid zwitterion barely change their acidity upon freezing. We discuss how acidity scales based on solid-state NMR measurements could be used to assess the degree of ionization of weak acids and bases in frozen media.

Adsorption of 2-X-benzoic acids (X = fluoro, chloro, and bromo) on Au(1 0 0) electrode in acidic media studied by IRAS

Adsorption behaviors of 2-fluoro-, 2-chloro-, and 2-bromobenzoic acids on Au(1 0 0) electrode in 0.1 M HClO 4 have been investigated by using in situ reflection adsorption IR spectroscopy and differential capacity measurements. It is found for the 2-substitued benzoic acids that the flat lying adsorbed species is present at negative potentials, and the vertically adsorbed benzoate with both oxygen atoms oriented toward the metal surface is present at positive potentials. A new adsorbed state due to the vertical orientation was observed around 0.75 V only in 2-fluorobenzoic acid solution, as well as the case of benzoic acid. This indicates that the new band is due to the formation of an ordered adsorption layer of the vertical 2-fluorobenzoate, and the formation of the arrangement adsorption is dependent on the size of the adsorbed molecule.

Synthesis of optically active aromatic poly(ether ketone)s containing 2,2′-bis (4-benzoylphenoxy)-1,1′-binaphthyl-6,6′-ene backbones

P 2O 5–MsOH mediated direct condensation of 2,2′-bis(4-benzoylphenoxy)-1,1′-binaphthyl ( 9) with 4-fluorobenzoic acid ( 10a) yielded the diaroylated monomer ( 11) in a moderate yield with the aid of P 2O 5–MsOH. The resulting monomer ( 11) was allowed to react with aromatic diols 2a- c, giving the corresponding optically active aromatic polyketones ( 6a– c). The resulting polyketones ( 6a– c) have high thermal resistance and excellent solubility to organic solvents.

Nanoparticle mediated photodefluorination monitored by 19F NMR

The photoreduction of monofluorinated phenols and benzoic acids on polyphosphate capped ZnS nanoparticles is examined. Defluorination is monitored using 19F NMR. Photoreductive defluorination on ZnS nanoparticles produces fluoride while direct photolysis produces ring opening products. Reaction on bulk ZnS produces ≪1% defluorination under the same conditions. The quantum yield and turnover numbers are presented for six compounds with the fluoride substituted at different positions around the aromatic ring. The reaction rates are affected by the presence of electron donating or withdrawing groups attached to the aromatic ring. The rates of product produced are 4-fluorophenol > 2-fluorophenol > 3-fluorophenol when the electron donating hydroxyl group is present and the opposite trend of 3-fluorobenzoic acid > 2-fluorobenzoic acid > 4-fluorobenzoic acid when an electron withdrawing group is attached to the benzene.

Conformational effects on vibronic spectra and excited state dynamics of 3-fluorobenzoic acid dimer

Two conformational isomers of 3-fluorobenzoic acid dimer (3-FBA(2)) have been identified in a supersonic jet expansion by use of laser-induced fluorescence excitation (FE), UV-UV hole-burning, and dispersed fluorescence (DF) spectroscopic methods. In the FE spectrum, the S(1) origins of the two isomeric species appear at a frequency gap of only 24 cm(-1), and the vibronic intensities of the redshifted dimer (dimer I) are about two times weaker than those of dimer II. However, ab initio quantum chemistry calculations at the MP2/6-31G(**) level of theory predict that all the isomeric species of 3-FBA(2) have almost the same binding energy (approximately 17 kcal/mol) in the ground state. Furthermore, unlike benzoic acid dimer, the present system shows intense activity for a low-frequency mode in both the FE and DF spectra. With the aid of DFT (B3LYP/6-311G(**)) predicted normal mode frequencies, we have assigned the mode to the in-plane gear (cogwheel) vibration of the cyclic hydrogen-bonded frame of the dimer. The Franck-Condon profiles for vibronic excitation of the mode indicate that the distortion of the cyclic hydrogen bond frame as a result of S(1)<--S(0) excitation is larger for dimer I than dimer II. Moreover, the fluorescence lifetime at the S(1) zero-point level of the former is also significantly smaller than the latter. Using the predictions of configuration interaction singles calculations, we have proposed that the spectral and dynamical differences between the two isomeric species observed in this study are manifestations of the different characteristics of their S(1) surfaces. By measuring FE, DF, and hole-burning spectra of a mixed dimer between 3-fluobenzoic acid and benzoic acid we have shown that the isomeric features in the homodimer spectra are due to two locally excited rotamers of the 3-fluorobenzoic acid moiety.

Inhibitory effects of 4-halobenzoic acids on the diphenolase and monophenolase activity of mushroom tyrosinase.

The effects of 4-halobenzoic acids (4-fluorobenzoic acid, 4-chlorobenzoic acid, and 4-bromobenzoic acid) on the activity of mushroom tyrosinase have been studied. The results show that 4-halobenzoic acids can strongly inhibit both monophenolase activity and diphenolase activity of the enzyme, and the inhibition displays a reversible course. The IC50 values were estimated as 0.26, 0.20, and 0.18 mM for diphenolase activity and as 1.03, 0.75, and 0.60 mM for monophenolase activity, respectively. Kinetic analyses show that the inhibition mechanism of all three 4-halobenzoic acids is noncompetitive inhibition to the diphenolase activity, and the inhibition constants (K1) were determined to be 0.25, 0.20, and 0.17 mM, respectively. The lag time of the monophenolase was obviously lengthened by these three 4-halobenzoic acids. When the concentration of inhibitors reached 1.4 mM, the lag time was lengthened from 30 s to 120, 125, and 150 s, respectively.

Synthesis of Some New Fluorine Containing Thiadiazolotriazinones as Potential Antibacterial Agents

2,4-dichloro-5-fluorophenyl, 4-fluoro-3-(Phenoxy)phenyl, 4-fluorophen-yl groups are known pharmacophores and can be used in the synthesis of new biologically active molecules. Therefore, 4-amino-6-arylmethyl-3-mercapto-1,2,4-triazin5(4H)-ones 1 are condensed with 3-phenoxy-4-fluoro-benzoic acid, 2,4-dichloro-5-fluorobenzoic acid, and 4-fluorobenzoic acid 2 to give 7-substituted-3-arylmethyl-4H-1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-ones 3 . Phosphorous oxychloride was used as cyclizing agent. All the newly synthesized compounds 3a-l was screened for their antibacterial activities. Most of them showed promising activity in the range of 10 w g/mL concentrations.

Clear Ag–Ag bonds in three silver(I) carboxylate complexes with high cytotoxicity properties

The reaction of Ag 2O and carboxylate ligands in ammonium solution results in three coordination polymers, [Ag(fbc)] n 1, [Ag 2(cpd)] n 2 and [Ag 2(idc)] n 3, where fbcH is 4-fluorobenzoic acid, cpdH 2 is cyclopentane-1,1-dicarboxylic acid and idcH 2 is iminodiacetic acid. The X-ray crystal structural analysis indicates that compounds 1 and 2 are two-dimensional frameworks and 3 is a three-dimensional framework. All the three complexes show clear Ag–Ag bonds and high cytotoxicity properties to normal cells and carcinoma cells. ▪

Selectivities in Reactions of Organolithium Reagents with Unprotected 2-Halobenzoic Acids

[reaction: see text] Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78 degrees C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b,c are trapped as such by chlorotrimethylsilane. In the absence of internal quench, 6Li-1b,c isomerize to the more stable 3Li-1b,c. The latter eliminate lithium halide and set free benzyne-3-carboxylate (2) that reacts regioselectively with LTMP to give 3-tetramethylpiperidinobenzoic acid (3).

Synthesis and Antimicrobial Activity of Some New Hydrazones of 4‐Fluorobenzoic Acid Hydrazide and 3‐Acetyl‐2,5‐disubstituted‐1,3,4‐oxadiazolines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and antimicrobial activity of some new hydrazones of 4-fluorobenzoic acid hydrazide and 3-acetyl-2,5-disubstituted-1,3,4-oxadiazolines

A series of hydrazide hydrazones and 1,3,4-oxadiazolines of 4-fluorobenzoic acid hydrazide were prepared and evaluated as potential antimicrobial agents and were tested for their antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. From these compounds, 4-fluorobenzoic acid[(5-nitro-2-furanyl)methylene]hydrazide ( 1a) showed equal activity with ceftriaxone against S. aureus. In addition, the MIC values of compounds 1c, 1d and 2a for the same strain were in the range of those reported for ceftriaxone according to NCCLS 1997.

Biodegradation studies of 4-fluorobenzoic acid and 4-fluorocinnamic acid: an evaluation of membrane inlet mass spectrometry as an alternative to high performance liquid chromatography and ion chromatography

The biodegradation of 4-fluorobenzoic acid (4-FBA) and 4-fluorocinnamic acid (4-FCA) has been monitored by membrane inlet mass spectrometry (MIMS) using a hollow-fibre silicone membrane. A novel in-membrane pre-concentration/thermal desorption (IMP-MIMS) technique was employed for MIMS analysis using an oven temperature profile that allowed semi-volatile organic compounds to be accumulated in the membrane and then released by rapid heating. Air drying of the membrane between the analyte pre-concentration and thermal desorption stages improved mass spectrometric performance by removing residual water from the membrane. The concentrations of 4-FBA and 4-FCA determined by MIMS compare well with data obtained by high performance liquid chromatography (HPLC). Stoichiometric amounts of fluoride were monitored using ion chromatography (IC). Intermediates in the biodegradation pathway were identified by liquid chromatography/mass spectrometry (LC/MS). These data establish the potential of MIMS as an alternative to chromatographic methods for monitoring the biodegradation of semi-volatile organic compounds.

Fluorine-18 labeled mouse bone marrow-derived dendritic cells can be detected in vivo by high resolution projection imaging

Immunization with ex vivo generated dendritic cells has become a focus for many clinical applications. The optimal site of injection and the migration pattern of these cells remain to be elucidated. We therefore developed a novel method for labeling mouse bone marrow-derived dendritic cells (BMDC) with the positron emitting radioisotope F-18 using N-succinimidyl-4-[F-18]fluorobenzoate, which covalently binds to the lysine residues of cell surface proteins. When we determined the stability of F-18 labeled BMDC, we found that at 4 h only 44±10% of the initial cell-bound activity was retained at 37 °C, whereas considerably more (91±3%) was retained at 4 °C. Labeled cells did not exhibit any significant alteration in cell viability or phenotype as determined by trypan blue exclusion and FACS analysis 24 h after radiolabeling. Furthermore, F-18-labeled BMDC stimulated allogeneic T cells in a mixed leukocyte reaction as potently as did sham-treated BMDC and migrated towards secondary lymphoid tissue chemokine (SLC) in a chemotaxis assay in vitro with the same efficiency as sham-treated BMDC. Migration of F-18-labeled BMDC was studied after footpad injection by (1) ex vivo counting of dissected tissues using a gamma counter and (2) in vivo by imaging mice with PiPET, a 2-mm resolution positron projection imager. After 4 h, the ratio between measured activity in draining vs. contralateral (D/C) lymph nodes (LN) was 166±96 ( n=7) in the case of live cell injections, whereas if we injected heat-killed F-18-labeled BMDC or F-18-labeled macrophages the D/C ratios were 17±2 ( n=2) and 14±4 ( n=2), respectively. Injection of cell-free activity in the form of F-18-labeled 4-fluorobenzoic acid resulted in a D/C ratio of 7±2 ( n=3), suggesting that the activity measured in the draining lymph node was associated with migrated F-18-labeled BMDC. When F-18-labeled live cells were injected into the footpad, 0.18±0.04% ( n=7) of footpad activity was found in the draining LN within 4 h, whereas none was found in the contralateral LN. Quantitative assessment of cell migration by PET projection imaging of mice confirmed the ex-vivo counting results. These studies indicate that PET imaging offers a new approach for in vivo studies of dendritic cell biodistribution and migration.