Reaction hazard analysis for cumene hydroperoxide with sodium hydroxide or sulfuric acid

Organic peroxides (OPs) are very susceptible to thermal sources, chemical pollutants or even mechanical shock. Over the years, they have caused many serious explosions. Cumene hydroperoxide (CHP) is widely employed to produce phenol and dicumyl peroxide (DCPO) in the manufacturing process. Differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were employed to determine the potential thermal hazards and thermokinetic parameters (such as exothermic onset temperature (T ₀), maximum temperature (T _max), and enthalpy (ΔH)) of CHP mixed with sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄). High performance liquid chromatography (HPLC) was used to analyze the concentration vs. time of CHP.When CHP is mixed with NaOH, the T ₀ is induced earlier and reactions become more intricate than the pure CHP solution. CHP added to NaOH or H₂SO₄ is more dangerous than pure CHP alone. Depending on the operating conditions, NaOH and H₂SO₄ are the incompatible chemicals for CHP.     

Layers of cyclam-substituted PVC with sodium hydroxide aqua complexes with aza-crown ligands on cellulose tissue filled with active coal

A material with an electrically ОН^–-conductive porous layer of cyclam-substituted PVC filled with active coal containing NaOH aqua complexes with aza-crown ligands and cross-linked with the surface of cellulose tissue fibers has been synthesized. The structure of the material was studied. Its sorption capacity in vapors and liquid benzene and hexane, specific resistance, potential of ОН^- transfer from solution to layer, and rate constants of ОН^– travel in the layer of the material as an electrochemical bridge in vapors and liquid benzene and hexane were determined. The aqua complexes decomposed in the layer with formation of Н₂ during the cathodic polarization of the bridge and О₂ during the anodic polarization; the composition of the complexes was regenerated due to the motion of ОН^–.     

Gelation/fusion behavior of PVC plastisol with a cyclodextrin derivative and an anti-migration plasticizer in flexible PVC

We successfully evaluated the effects of 2,3,6-per-O-benzoyl-β-cyclodextrin (Bz-β-CD) on the rheological properties of PVC plastisols and the migration behavior of plasticizer from flexible PVC. Two types of plasticizer, di-isononyl phthalate (DINP) and diisononyl cyclohex-4-ene-1,2-dicarboxylate (Neocizer), along with Bz-β-CD as a migration inhibitor were mechanically mixed into an emulsion grade PVC resin to prepare plastisols. The presence of Bz-β-CD was expected to facilitate formation of stable complexes with DINP or Neocizer in the flexible PVC. It was necessary to determine whether changes in the processing conditions of the PVC plastisol were needed for use in this application. To this end, the viscoelastic properties of the plastisols, including the elastic modulus, G′, and the viscous modulus, G″, were continuously monitored as a function of temperature during the gelation and fusion processes using rheological analysis techniques. The results showed that complete gelation was slightly delayed and both moduli (G′ and G″) decreased upon addition of Bz-β-CD to the PVC matrix. FE-SEM images yielded insight into the gelation and fusion processes. The curing conditions and physical properties of the flexible PVCs containing Bz-β-CD were optimized, and the influence of Bz-β-CD on the migration of the plasticizers and the stability of the flexible PVC was studied. The results showed that Bz-β-CD reduced migration of DINP and Neocizer from the flexible PVC by almost 40% and 25%, respectively, thereby favorably restricting migration within the flexible PVC.     

Spectrophotometric flow injection determination of l-ascorbic acid with a packed reactor containing ferric hydroxide

A flow injection system with spectrophotometric detection is proposed for determining l-ascorbic acid in pharmaceutical formulations. In this system a column containing Fe(OH)(3) immobilized in polyester resin (packed reactor) is inserted before the detector. Fe(III)-1,10-phenanthroline complex is reduced by l-ascorbic acid to produce Fe(II)-1,10-phenanthroline complex which is monitored at 510 nm. Under the optimum analytical conditions, the linearity of the calibration equation for l-ascorbic acid ranged from 5.0x10(-6) to 6.0x10(-5) M of added amount. The detection limit was 5.0x10(-7) M and recoveries between 98.5-102.0% were obtained. No interference was observed from the common excipients of pharmaceutical formulations and other active substances such as acetylsalicylic acid, caffeine and thiamine.     

A specific chemodosimeter for fluoride ion based on a pyrene derivative with trimethylsilylethynyl groups

Pyrene derivative 1 containing four trimethylsilylethynyl substituents was synthesized and investigated as a chromogenic and fluorescent chemodosimeter sensor for fluoride ions. 1 showed a high sensitivity and specific selectivity over a rapid response time toward fluoride anions compared to other anions, such as Cl(-), Br(-), ClO(4)(-), H(2)PO(4)(-) and HPO(4)(2-). TD-DFT calculations showed that the delocalization of the σ-electrons of the silicon destabilized the HOMO energy level of 1, thus red shifting both its absorption and emission spectrum. The addition of F(-) removed the trimethylsilyl substituents and resulted in a blue shift of both the absorption and fluorescent spectra of 1, which could be monitored by the color change with the naked-eye. Moreover, an easy to prepare test paper, which was obtained by immersing a filter paper into a THF solution of 1, could be utilized to detect and estimate the concentration of fluoride anions in water.     

Stereoselective synthesis of a new chiral synthon: a cyclic pseudodipeptide containing an aspartic acid derivative and l-valine

A simple stereoselective synthesis of cyclic synthons 4a,b and 10a,b, derived from an l-valine unit and an unnatural derivative of the aspartic acid, has been accomplished starting from the chiral synthon 1 and following the procedure already reported by us for the synthesis of similar compounds. These cyclic synthons are interesting substrates because they can behave as both electrophiles and nucleophiles and could be useful starting materials for the preparation of higher peptides such as, for instance, the unnatural tetrapeptides 15 and 18, through the condensation of 4a with 6a or 13 with 17, respectively.     

Materials based on carbon-filled porous layers of PVC cyclam derivatives cross-linked with the surfaces of asbestos fabric fibers

The synthesis of bilayer materials with porous upper layers composed of PVC hydroxyethylcyclam derivatives filled with carbon and a layer consisting of hydroxyethylcyclam, cross-linked via Si–O–C groups with the silica chains of a developed surface of asbestos fabric, is described. The aza-crown groups in these materials are bound with aqua complexes of H₂SO₄ or NaOH. The structure of the materials is examined, their adsorption characteristics are determined, and the rate of motion of H⁺ or OH^– ions in electrochemical bridges is measured, while the formation of H₂ and O₂ in their cathodic and anodic polarization is determined as a function of voltage. It is shown that the upper layer of these materials is adsorption-active and electronand H⁺- or OH^–- conductive, while the bottom layer is only H⁺- or OH^–- conductive; through it, the upper layer is supplied with the H⁺ or OH^– ions needed for the regeneration of the aqua complexes broken down to H₂ and O₂ on carbon particles.     

Performance testing of a green plasticizer based on lactic acid for PVC

In order to develop alternative green plasticizers, a bio-based plasticizer, acetylated lactic acid 1,4-cyclohexanedimethyl ester(ALCH), with novel molecule geometry was synthesized from l-lactic acid and characterized by FTIR, ¹H NMR and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The prepared ALCH was mixed with poly(vinyl chloride) (PVC) as plasticizer and the results indicated that the PVC films plasticized by ALCH have better migration and volatility stability than acetyl tributyl citrate (ATBC). In addition, ALCH could endow PVC products with excellent performance of strength, elongation and elasticity. With the substitution of ALCH for ATBC, glass transition temperature (Tg) of PVC films decreased gradually from 61.3°C to 55.0 °C. The self-polymerization of lactic acid gives ALCH better plasticizing effectiveness than ATBC.     

Crystal structures of crown ethers containing an alkyl diarylphosphinate or a diarylphosphinic acid unit

This paper describes the structures of pseudo-18-crown-6 compounds (2, R,R-4 and 5) in the crystals together with theoretical calculations of the electronic circular dichroism (ECD) spectra. The achiral macrocyclic phosphinic acid 5 forms hydrogen-bonded dimers in the crystal. The O1–O2 distance (2.489 Ǻ) indicates strong H-bondings. The conformations of the macrorings of the achiral phosphinate 2 and the monomers of the achiral phosphinic acid 5 are chiral. A comparison of the torsion angles of the achiral methyl phosphinate 2 and the monomeric units of achiral 5 indicates a similar geometry. The torsion angles of the chiral methyl phosphinate (R,R)-4 differ more significantly from those in achiral methyl phosphinate 2. A negative ¹B_b exciton couplet was observed in the ECD spectrum of monomeric (R,R)-6 in MeOH and H₂O as in the spectra of (R,R)-4 in all solvents. To support the idea that (R,R)-4 has basically the same conformation in the crystal and in solution, the ECD spectrum of (R,R)-4 was calculated using the geometry of the molecule in the crystal. The calculated ECD spectrum shows a reasonable agreement with the ECD spectra obtained in solution. This shows that the steric structure observed in the crystal is predominant in solution as well.     

A spectral study of transition-metal complexes on a chelating ion-exchange resin containing aminophosphonic acid groups

The coordination mode of a commercial chelating ion-exchange resin, ES 467, containing aminomethylphosphonic acid groups anchored on a macroporous styrenedivinylbenzene copolymer, with several metal ions, such as chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II) has been studied with the aid of IR, ligand field and ESR spectra. The chelating group of ES 467, aminomethylphosphonic acid, appears to bind different metal ions mainly through oxygen atoms of the phosphonic acid group, though, in the case of those species containing low-loading of metal ions, the secondary amine nitrogen atom also appears to take part in coordination. Most of the metal ions studied seem to be present as six-coordinated species in the polymeric matrix, whereas cobalt(II) species show electronic spectra which are consistent with the presence of both four-coordinated (tetrahedral) and six-coordinated (octahedral) structures of these species. The distribution coefficients for cobalt(II), nickel(II), copper(II) and zinc(II) have been determined and it appears that the resin ES 467 binds copper(II) ions selectively. An attempt has been made to find a possible relationship between the selectivity of the chelating resin and the stereochemistry of the adsorbed metal ions.     

Mesoporous silica materials with an extremely high content of organic sulfonic groups and their comparable activities with that of concentrated sulfuric acid in catalytic esterification

Mesoporous silica materials (HS-JLU-20) with an extremely high content of mercaptopropyl groups have been successfully synthesized using fluorocarbon-hydrocarbon surfactant mixtures through a simple co-condensation approach of tetraethyl orthosilicate (TEOS) and (3-mercaptopropyl)trimethoxysilane (MPTS), which are characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms, transmission electron microscopy (TEM), CHNS elemental analysis, thermogravimetry analysis (TGA), and (29)Si NMR spectroscopy. The results show that HS-JLU-20 samples with molar ratios of MPTS/(MPTS + TEOS) at 0.5-0.8 in the starting synthetic gels still show their mesostructures, while HS-SBA-15 with the molar ratio of MPTS/(MPTS + TEOS) at 0.50 completely loses its mesostructure in the absence of fluorocarbon surfactant. Possibly, fluorocarbon surfactant containing N(+) species with a positive charge could effectively interact with negatively charged mercapto groups in the synthesis of HS-JLU-20 materials, resulting in the formation of mesoporous silicas with good cross-linking of silica condensation even at an extremely high content of organic mercapto groups. More interestingly, after the treatment with hydrogen peroxide, HSO(3)-JLU-20 materials with an extremely high content of organic sulfonic groups exhibit comparable activity with liquid concentrated sulfuric acid in catalytic esterification of cyclohexanol with acetic acid.     

Chiral sensing for amino acid derivative based on a [2]rotaxane composed of an asymmetric rotor and an asymmetric axle

A racemic [2]rotaxane, composed of an asymmetric rotor and an asymmetric axle, formed a diastereomer with an amino acid derivative, and showed an optical response for the chiral recognition.     

Preparation and characterization of humidity sensor based on poly(3-alkyl)pyrrole containing phosphonic acid groups

Poly(3-alkyl)pyrroles containing phosphonic acid groups with different alkyl segment lengths were chemical synthesized and the properties were measured by FTIR and UV-Vis spectroscopy. FTIR and UV-Vis results showed that the synthesized polymers were in a low doping level through chemical polymerization. By spin-coating on the surface of substrates, the polymer can be used as a humidity sensor. The change of DC electric current of the polypyrroles varies with the chain length of the alkyl substituents. The capacitance increases with the increase of the humidity and resistance decreases with the increase of humidity. This result is different from that of polypyrrole without alkyl substituents due to the influence of the phosphonic acid group. The sensor showed the resistive-type at high relative humidity, and the capacitivetype at the low relative humidity. The sensor exhibited very fast response to the change of environment humidity.     

Synthesis and preliminary studies on novel enantiopure crown ethers containing an alkyl diarylphosphinate or a proton-ionizable diarylphosphinic acid unit

This paper reports the synthesis, characterization and electronic circular dichroism (ECD) spectroscopic studies of a new type of crown ethers and their achiral analogues containing a tetrahedral phosphorous centre. The synthetic routes to the two chiral phosphinate derivatives [(R,R)-10 and (R,R)-11] were similar, starting from the earlier reported ethyl bis(2-hydroxyphenyl)phosphinate and the unreported methyl bis(2-hydroxyphenyl)phosphinate, respectively. The enantiopure crown ether containing phosphinic acid unit (R,R)-14 was obtained by hydrolysis of the phosphinates (R,R)-10 and (R,R)-11, respectively. ECD spectroscopy was used for investigation of the chiroptical properties as well as complex formation ability of the novel enantiopure ligands. Owing to the presence of the aryl substituents the ECD spectra are rich in bands in the ¹B_b, ¹L_a and ¹L_b regions (190-250 nm and 260-330 nm, respectively). In the case of (R,R)-14, a solvent dependent conformational behaviour was observed due to the strong dimer or aggregate forming ability of the POOH groups. This finding was supported by theoretical calculation of the monomer and the dimer forms. Phosphinates (R,R)-10 and (R,R)-11 form complexes with α-phenylethylammonium perchlorate (PEA) and α-(1-naphthyl)ethyl ammonium perchlorate (NEA) but do not discriminate between their enantiomers. All three chiral crown ethers bind strongly cations of ionic radii <∼1 Å.     

Ligand concentration-dependent supramolecular complexes with uncoordinated carbonyl groups based on a new pyrazole carboxylic acid ligand

One new pyrazole-based ligand, 1-carboxymethyl-3,5-dimethyl-1H-pyrazole-4-carboxylic acid (H₂cmdpca), has been synthesized and characterized. Structural analysis reveals that H₂cmdpca crystallizes in the monoclinic system and adopts a 3-D supramolecular network via the interaction of intermolecular hydrogen bonds. The reactions of Cd(II) ions with H₂cmdpca and 4,4′-bipyridine (4,4′-bpy) afforded three metal complexes, [Cd(4,4′-bpy)(Hcmdpca)₂(H₂O)₃]·H₂O (1), [Cd(4,4′-bpy)(Hcmdpca)₂(H₂O)]·3H₂O (2), and [Cd(4,4′-bpy)(Hcmdpca)₂(H₂O)] (3). Structural analyses reveal that these complexes are all monoclinic and 1, 2, and 3 exhibit mononuclear, 1-D chain, and 1-D with binuclear loop structures, respectively, which are further assembled into 3-D supramolecular frameworks through non-covalent interactions. 1 and 2 are true supramolecular isomers, while 2 and 3 are “pseudo-supramolecular” isomers. In addition, the thermal stability and luminescent properties of the complexes are also investigated.     

Ion-exclusion chromatographic behavior of aliphatic carboxylic acids and benzenecarboxylic acids on a sulfonated styrene--divinylbenzene co-polymer resin column with sulfuric acid containing various alcohols as eluent

The addition of C1-C7 alcohols (methanol, ethanol, propanol, butanol, heptanol, hexanol and heptanol) to dilute sulfuric acid as eluent in ion-exclusion chromatography using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as the stationary phase was carried out for the simultaneous separations of both (a) C1-C7 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, 2-methylvaleric, isocaproic, caproic, 2,2-dimethyl-n-valeric, 2-methylhexanoic, 5-methylhexanoic and heptanoic acids) and (b) benzenecarboxylic acids (pyromellitic, hemimellitic, trimellitic, o-phthalic, m-phthalic, p-phthalic, benzoic and salicylic acids and phenol). Heptanol was the most effective modifier in ion-exclusion chromatography for the improvement of peak shapes and a reduction in retention volumes for higher aliphatic carboxylic acids and benzenecarboxylic acids. Excellent simultaneous separation and relatively highly sensitive conductimetric detection for these C1-C7 aliphatic carboxylic acids were achieved on the TSKgel SCX column (150 x 6 mm I.D.) in 30 min using 0.5 mM sulfuric acid containing 0.025% heptanol as eluent. Excellent simultaneous separation and highly sensitive UV detection at 200 nm for these benzenecarboxylic acids were also achieved on the TSKgel SCX column in 30 min using 5 mM sulfuric acid containing 0.075% heptanol as eluent.     

Chemiluminescence behavior based on oxidation reaction of rhodamine B with cerium(IV) in sulfuric acid medium

The chemiluminescence (CL) of the rhodamine B (RhB)-cerium(IV) system was investigated by flow-injection. Rhodamine B was suggested to be a suitable chemiluminescent reagent in acidic conditions. When the concentration of rhodamine B was 100 mg l⁻¹ and cerium sulfate was 1.6 mmol l⁻¹ in sulfuric acid, the chemiluminescent intensity was found to be highest by using 0.3 mol l⁻¹ sulfuric acid as a carrier solution. The particular chemiluminescent system could tolerate such distinct acidic environments that it was utilized for detecting many compounds that are stable in acidic solutions. Furthermore, by virtue of IR, UV-Vis and luminescence spectroscopic measurements, the chemiluminescent behavior of rhodamine B was studied and a possible mechanism for this chemiluminescent reaction was proposed. The emitter was affirmed to be a radical species due to one of the oxidation products of RhB; the chemiluminescent emissive wavelength was about 425 nm.