Attempt to incorporate ferrocenecarboxylic acid into polypyrrole during the electropolymerization of pyrrole in chloroform: its application to the electrocatalytic oxidation of ascorbic acid

 In this work, polypyrrole films with ferrocenecarboxylic acid incorporated (PPy/FCA) were prepared on a glassy carbon (GC) electrode in chloroform as an aprotic solvent with low dielectric constant, convenient for the preparation of the films by a precipitation mechanism. The electrochemical behaviour of the PPy/FCA-coated GC electrode was studied by cyclic voltammetry in aqueous solution with low pH. The results obtained show that the electrochemical response of FCA incorporated in polypyrrole is consistent with a reversible surface oxidation. An obvious electrocatalytic effect of PPy/FCA on the oxidation of ascorbic acid is observed in aqueous solution. Received: 30 July 1998 / Accepted: 3 March 1999     

Selective Analysis of Secondary Amines Using Liquid Chromatography with Electrochemical Detection (LC‐EC)

In a mixture of primary and secondary aliphatic amines, the primary amines were derivatized (masked) with o‐phthalaldehyde (OPA) followed by derivatization of the remaining secondary amines with ferrocenecarboxylic acid chloride (FAC). The “tagged” amines were analyzed by LC‐EC (liquid chromatography with electrochemical detection) using in‐series dual electrode detection. Chemically‐reversible oxidation of the FAC tagged secondary amines and their subsequent complementary oxidation and reduction signals coupled with chemically‐irreversible oxidation of OPA tagged primary amines provided the selectivity for quantitative secondary amine analysis. The procedure was also applied for the selective identification of fragment 4–11 (N‐terminus‐proline) of Substance P in the presence of other Substance P fragments with primary amino acids as their N‐termini.     

Coerced photodimerization reaction in the solid state through amine salt formation

Photodimerization of fumaric or several γ-form trans-cinnamic acids proceeded successfully in the solid state through amine salt formation with ammonia or some aromatic heterocyclic amines (especially, imidazole). It appears that this success is due to a small size or a planar structure of the amine. A layered or a channel-type clathrate crystal structure was revealed, respectively.     

Synthesis,structure and catalytic properties of Pdii-based bimetallic complexes with ferrocenecarboxylic acid

Novel highly soluble palladium-based complexes with ferrocenecarboxylic acid of general formula [Pd(lut)₂(FcCOO)₂] (lut is 2,6-or 3,4-lutidines) were synthesized and structurally characterized by single-crystal X-ray diffraction. The catalytic oxidation of 1,2-diphenyl-acetylene with these complexes gave dibenzo[a,e]pentalene derivative along with other products.     

An investigation about the solid state thermal degradation of acetylsalicylic acid: polymer formation

An investigation about the thermal degradation of acetylsalicylic acid (ASA) is performed. It is verified that the thermal degradation of ASA produces not only salicylic acid (SA) and acetic acid (AA) as products but also an ASA polymer, which is transparent and solid. And also verified that the temperature in which the polymer is obtained influences its physical consistence (solid or semi-solid). Furthermore, the ASA polymer is very stable from a thermic point of view, as verified by TG and DSC analysis. X-ray diffraction patterns obtained for the ASA polymer show that it exhibits a low crystallinity.     

Enantioresolution of 2-methoxy-2-(1-naphtyl)propionic acid using diastereomeric salt formation with chiral phenylethylamine

An enantioresolution of 2-methoxy-2-(1-naphtyl)propionic acid (MαNP acid) using the diastereomeric salt with chiral (R)-phenylethylamine was achieved to give enantiopure (R)-MαNP acid in 29% yield with >99% ee based on rac-MαNP acid. X-ray crystallographic analysis of diastereomeric salt revealed that (R)-MαNP acid was tightly arranged by four independent hydrogen bonds and one CH–π interaction with (R)-phenylethylamine.     

Electrochemical studies on the composition,stability constants and thermodynamics of TI(I) complexes with dithiodipropionic acid

The composition and stability constants of Tl(I) complexes with dithiodipropionic acid have been studied employingLingane's polarographic method,Calvin-Melchior'spH-metric technique, and conductance measurements. The thermodynamic functions G, H and S involved in complex formation are also determined at 30°C.

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Elektrochemische Untersuchungen von Zusammensetzung, Stabilitätskonstanten und Thermodynamic von Tl(I)-Komplexen mit Dithiodipropionsäure

Zusammenfassung Die Zusammensetzung und die Stabilitätskonstanten von Tl(I)-Komplexen mit Dithiodipropionsäure wurde mittels polarographischer Methoden (nachLingane),pH-metrischer Titration (nachCalvin-Melchior) und Leitfähigkeitsmessungen untersucht. Die thermodynamischen Funktionen der Komplexbildung (G, H und S) wurden bei 30°C bestimmt.

     

Sensing and formation of a stable gel in the presence of picric acid by a low-molecular-weight-gelator

In this work, a set of amide-based compounds, L1-L3, have been studied. These compounds are decorated with various H-bonding functional groups while the presence of aromatic rings not only promote π?π stacking but also made these molecules electron-rich. All three compounds were utilized for the sensing of electron-deficient nitro-explosives. These compounds were found to be highly selective for the nanomolar sensing of picric acid (PA). Out of three compounds, L3 acted as a low-molecular-weight-gelator and formed a more stable and stronger gel in the presence of PA. The resultant [email protected]L3?gel was studied by the SEM, powder XRD and rheological techniques while further supported by the molecular docking studies. These results illustrate that doping of L3 with PA not only enhances several noteworthy interaction avenues but also the stability of the resultant [email protected]L3?gel when compared to L3?gel.     

Solvent dependent dimercaptothiadiazole monolayers on gold electrode for the simultaneous determination of uric acid and ascorbic acid

Dimercaptothiadiazole compound, 2,5-dimercapto-1,3,4-thiadiazole (DMcT) forms ‘thin’ monolayers on Au electrode when it was adsorbed from methanol, ethanol or DMSO solutions while it forms ‘thick’ layers on Au electrode from an aqueous solution under identical experimental conditions. Thick DMcT layers formed from aqueous solution effectively blocks the redox reaction of couple in contrast to thin DMcT monolayers. The monolayer thickness did not vary when structurally related DMcT compounds, 5-methyl-1,3,4-thiadiazole-2-thiol or 5-amino-1,3,4-thiadiazole-2-thiol was adsorbed from aqueous and non-aqueous solutions. This indicates that the presence of two thiol groups in DMcT plays a crucial role in the formation of thick and thin DMcT layers on Au electrode when it was adsorbed from aqueous and non-aqueous solutions. Methanol, ethanol, or DMSO solution of DMcT is considered as strong acid because these solvents are able to deprotonate DMcT into DMcT⁻ and thus thin monolayers formed on Au electrode. The deprotonating ability of these solvents was further verified from the observed absorption spectrum characteristic of DMcT⁻ species. On the other hand, an aqueous solution of DMcT is less acidic due to weak deprotonation of DMcT by water and thus DMcT forms thick layer on Au electrode. Interestingly, thin DMcT monolayers formed from non-aqueous solvents separates the voltammetric signals of uric acid and ascorbic acid while thick DMcT layers formed from aqueous solution fails to separate them.     

Electrosynthesis of heteroaromatic aldehydes by palladium-catalyzed carbonylation of heteroaromatic iodides in the presence of formic acid

The palladium-catalyzed electrocarbonylation of heteroaromatic iodides, performed in the presence of formic acid under one atmosphere of carbon monoxide, affords heteroaromatic aldehydes in moderate to good yields. It has been developed a new application of palladium-catalyzed formylation using carbon monoxide, formic acid and tertiary amines as ligands under electrochemical reducing conditions.     

A synergetic effect in nitrous acid formation by sonolysis of nitric acid in the presence of nitrous oxide

A synergetic effect is found in the sonochemical formation of HNO₂ in HNO₃ solution in the presence of an N₂O–Ar gaseous mixture. The maximum rate of HNO₂ formation is observed at an N₂O : Ar ratio of 15 : 85 (v/v). During the sonolysis of 4 M HNO₃ solutions, the rate of HNO₂ formation increases multifold due to the synergetic effect. The rate of sonochemical hydrazine decomposition in nitrate solutions also increases considerably in the presence of N₂O.     

Influence of spacer in the formation of nanorings by templateless electropolymerization

In this original work, we want to control the shape of the resulting porous structures by templateless electropolymerization, by adjusting the spacer (flexible alkyl chains or rigid aromatic groups) between thieno[3,4-b]thiophene and carbazole used as the monomer and the substituent, respectively. A huge change is especially observed from ribbon-like structures to nanorings as the alkyl spacer increases. The presence of a significant amount of water is necessary for the formation of these porous structures because it allows releasing a high amount of gas bubbles. The size and number of nanorings are dependent on both the alkyl spacer and electrochemical parameters such as the number of deposition scans. These surfaces could be used in the future in various potential applications such as in water harvesting, oil/water separation membranes, optical devices, sensors or photocatalysis.     

Microwave assisted one-pot synthesis of novel molecular clefts with only one chiral arm based on deoxycholic acid

A rapid, safe, and efficient method for the synthesis of novel molecular clefts based on deoxycholic acid was reported. Seven new molecular clefts have been synthesized in good yields （89-98%）. This method proved to be extremely simple and highly efficient. The structures of these receptors were confirmed by 1H NMR, IR, MS spectra and elemental analysis. 2007 Zhi Gang Zhao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Direct formation of chromopyrrolic acid from indole-3-pyruvic acid by StaD, a novel hemoprotein in indolocarbazole biosynthesis

Indole-3-pyruvic acid was transformed to chromopyrrolic acid by a novel heme-containing enzyme StaD responsible for staurosporine biosynthetic pathway in Streptomyces sp. TP-A0274.     

Dynamic and equilibrium swelling of a sulfonic acid superabsorbent copolymer in salt solutions

Superabsorbent copolymers were synthesized by free radical reverse emulsion from the monomers acrylamide and 2‐acrylamido‐2‐methyl‐propanosulfonic acid with a divinyl crosslinker (methylene‐bisacrylamide). The copolymer synthesized was then identified by Fourier transform infrared spectroscopy, its porosity was examined by electronic microscopy, and its specific gravity was determined by the conventional procedure. The dynamic and equilibrium swelling behavior of the copolymer was studied, in water and in salt solutions, at 25 °C (chlorides and sulfates of sodium and magnesium). As to the equilibrium swelling, the influence of the pH as well as of the salt type and its concentration was observed. As to the dynamic swelling, it was interpreted in terms of both a simple power of time equation, and a more detailed model based on a coupled diffusion‐relaxation mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 505–514, 2004     

Trifluoromethanesulfonic acid as a catalyst for the formation of dansylhydrazone derivatives

Trifluoromethanesulfonic acid (TFMSA) is presented as a new, efficient catalyst in the pre-column fluorescent derivatization of the 3-ketosteroid budesonide with dansylhydrazine and compared to the commonly used catalyst trifluoroacetic acid. With TFMSA the derivatization reaction may be carried out at room temperature, with a considerably higher reaction rate compared to previously used acids. The chromatograms also show that TMFSA results in less formation of spurious peaks from the reagent. Derivatization of steroid solutions ranging from 0.5 to 64 μM could be performed using identical reaction conditions.     

Heterogeneous reactions of gaseous methanesulfonic acid with NaCl and sea salt particles

Methanesulfonic acid (MSA) has been identified as one of the most important intermediate products of DMS reactions in the atmosphere. Although considerable amounts of MSA have been found in the marine boundary layer, little is known about the interaction of gaseous MSA with sea salt particles. To understand the fate of MSA in the atmosphere and its potential importance in atmospheric chemistry, the heterogeneous reactions of gaseous MSA with micron-scale NaCl and sea salt particles were studied using diffuse reflectance infrared Fourier transform spectrometry, X-ray photoelectron spectroscopy, and scanning electron microscopy. The CH₃SO₃Na and CH₃SO₃ ⁻ were the major products of the condensed phase of the reaction of gaseous MSA with NaCl and with sea salt particles. The steady-state uptake coefficient was determined to be (5.94±2.32)×10⁻⁷ (1 σ) for the reaction of gaseous MSA with NaCl particles and (2.23±1.25)×10⁻⁷ (1 σ) for the reaction of gaseous MSA with sea salt particles. The heterogeneous reaction of MSA with NaCl particles was found to be first-order for MSA. The reaction mechanisms were discussed. Supported by the National Natural Science Foundation of China (Grant No. 40490265) and the National Basic Research Priorities Program (Grant No. 2002CB410802)     

Electroanalytical evidence for the formation of carbinolamines in the reactions of terephthalaldehyde with hydrazine

Electroanalytical techniques enable the detection and following of time changes of three intermediates (two carbinolamines and one monohydrazone) in the reaction of terephthalaldehyde with hydrazine at pH 7.3.     

Determination of citric acid by means of competitive complex formation in a flow injection system

A photometric method for the determination of citrate and other organic acids based on their ability to complex Fe³⁺-ions is presented. The red colored complex of [Fe(SCN)₂]⁺, used as reagent, is destroyed upon contact with the sample because the organic acid complexes the Fe³⁺-ion. The decrease in absorption is monitored at 460 nm. The reaction is carried out in a simple flow injection system either in single or preferably double channel configuration.The influence of pH was investigated. Best results were obtained by adjusting the carrier stream to pH 2.0–2.5 with a KCl/HCl-buffer. With an increasing concentration of reagent the linear range is shifted to higher citrate concentrations. The slope of the calibration graph and the linear range are influenced by the sample volume. Other variations of parameters include flow rate, reactor volume and diameter of tubing. Generally speaking, optimum conditions for the flow system are not specified because they vary with the application.The typical conditions for a calibration graph from 1 to 8 mmol/l citrate were a reagent concentration of 2.6 mmol/l [Fe(SCN)₂]⁺, a flow rate of 2.4 ml/ min, a reactor length of 50 cm with tubing of 0.97 mm inner diameter and a sample volume of 100 l. At these system settings the coefficients of variation were 2.5% and 1.6% for eight replicate measurements of samples containing 4 mmol/l and 8 mmol/l citrate, respectively. Up to 180 samples can be analyzed per hour.Naturally the method is disturbed by all other ions that form complexes or precipitates with Fe³⁺-ions. Therefore its application is limited to samples with a known matrix, which was given in the analysis of citrate in lemon flavored soft drinks, where the citric acid usually accounts for 95 to 99% of the total acidity and other interfering ions are absent.