Aromatic hydroxylation with peroxymonophosphoric acid

Aromatic hydroxylation of mesitylene, phenol and anisole (ArH) with peroxymonosphosphoric acid (H₃PO₅) in acetonitrile has been studied. H₃PO₅ is shown to be an effective reagent for aromatic hydroxylation, the reactivity being comparable to that with CF₃CO₃H. Mesitylene gives mesitol (over 70%). The hydroxylation with H₃PO₅ is ca 100 fold faster than that with MeCO₃H or PhCO₃H. The rate equation is: v = k₂[ArH][H₃PO₅] instead of our previous one. The oxidation is catalyzed by H₂SO₄, giving a linear plot of log k₂ vs H₀ with a slope of 1.26 for phenol and 1.17 for mesitylene.     

Hydroxyl radical mediated degradation of phenylarsonic acid

Phenyl-substituted arsonic acids have been widely used as feed additives in the poultry industry. While very few studies have been reported on the environmental impact of these compounds, they have been introduced into the environment through land application of poultry litter in large quantities (about 10(6) kg/year). Phenylarsonic acid (PA) was used as a model for problematic arsonic acids. Dilute aqueous solutions of PA were subjected to gamma radiolysis under hydroxyl radical generating conditions, which showed rapid degradation of PA. Product studies indicate addition of (.)OH to the phenyl ring forms the corresponding phenols as the primary products. Arsenite, H3As(III)O3, and arsenate, H3As(V)O4, were also identified as products. The optimized structures and relative calculated energies (using GAUSSIAN 98, the B3LYP/6-31G(d) method) of the various transient intermediates are consistent with the product studies. Pulse radiolysis was used to determine the rate constants of PA with (.)OH (k = 3.2 x 10(9) M(-1) s(-1)) and SO4(.-) (k = 1.0 x 10(9) M(-1) s(-1)). PA reacts slower toward O(.-) (k = 1.9 x 10(7) M(-1) s(-1)) and N3(.) (no detectable transient), due to the lower oxidation potential of these two radicals. Our results indicate advanced oxidative processes employing (.)OH and SO4(.-) can be effective for the remediation of phenyl-substituted arsonic acids.     

Transformation of organic and inorganic compounds in trifluoroacetic acid

It is established that the effectiveness of fluorine-containing acids in the transformation of organic and inorganic substrates is due to the ability of the acid to perform several functions: to accumulate relatively high concentrations of molecular oxygen, to activate it, and to serve as a hydrogen-containing medium.     

Aromatic nucleophilic substitution or CuI-catalyzed coupling route to martinellic acid

Condensation of beta-amino ester 8b with triflate 7 gives N-aryl amino ester 11, which is converted into 2-substituted 4-oxoquinoline 4 using an intramolecular Dieckmann reaction as the key step. CuI-mediated coupling of beta-amino ester 8a with 1,4-diiodobenzene followed by an intramolecular acylation and Pd-catalyzed carbonylation provide another manner to 4. Alkylation of 4 and subsequent reductive amination deliver the cyclic imine 14, which is transformed into triamine 3 by ordinary operations. Guanylation of 3 under mild condition followed by deprotection results in the synthesis of martinellic acid 1.     

Organic acid solutions in the chromatography of inorganic ions

Summary We present a study of the chromatographic behaviour of sixty ions on thin layers of cellulose, employing as eluents aqueous solutions of tartrate, at various molarities (from 0.1 to 1.0 mol dm^–3 and pH values (from 2.0 to 10.0 obtained with aqueous ammonia). The ions migrate, whether they are complexed with the tartrate or not, with high R_F values and are not influenced by variation of the tartrate concentration. The pH variations, owing to the formation of partial hydrolysis or precipitation products or possibly ammonia complexes, have a greater effect on the rate of ion migration and cause a decrease in the R_F values. We show interesting separations obtained with these eluents.This work has been in part supported by C.N.R. of Italy     

Proton mobility in hydrates of inorganic acids and acid salts

Published data on the mechanisms of hydrogen ion transport in solids and aqueous solutions are described systematically, including defect formation, rotational mobility of proton-containing groups, proton hopping along a hydrogen bond, proton translational mobility, and proton conduction. Resorting to the authors" theoretical results and published data, the main criteria for the selection of systems possessing high proton mobility are formulated.     

Metal-mediated formation of gas-phase amino acid radical cations

The results from an investigation of the collision-induced dissociation (CID) of the ternary complexes [Cu(II)(terpy)(AA)](2+) are presented (terpy = 2,2':6',2' '-terpyridine; AA = one of the twenty common amino acids). These complexes show a rich gas-phase chemistry, which depends on the identity of the amino acid. For the histidine-, lysine- and tryptophan-containing complexes, oxidative dissociation of the amino acid is observed, yielding the amino acid radical cation. The results of further mass selection and CID of these amino acid radical cations are presented. The CID of the series [Fe(III)(salen)(AA)](+) (where salen = N,N'-ethylenebis(salicylideneaminato)) is also examined. These complexes undergo loss of the neutral amino acid in all cases, although the radical cation of arginine is also produced and its subsequent fragmentation examined. B3-LYP/6-31G(d) computations were carried out to test aspects of the proposed fragmentation mechanism of the histidine and arginine radical cations.     

Asymmetric radical polymerization of butadiene 1-carboxylic acid

Optically active S(?)-α-phenethylammonium butadiene 1-carboxylate was prepared and polymerized in methanol, using azobisisobutyronitrile as initiator. The optical rotation, optical rotatory dispersion and circular dichroism spectra of the polymers, before and after removal of chiral amine, have demonstrated that the asymmetric induction occurred in the main chain. An asymmetric inductive polymerization mechanism is discussed.     

A new technique to determine organic and inorganic acid contamination

A new acid indicator pad was developed for the detection of acid breakthrough of gloves and chemical protective clothing. The pad carries a reagent which responds to acid contaminant by producing a color change. The pad was used to detect both organic and inorganic acids permeating through glove materials using the modified ASTM F-739 and direct permeability testing procedures. Breakthrough times for each type of glove were determined, and found to range from 4 min to > 4 h for propionic acid, from 3 min to > 4 h for acrylic acid, and from 26 min to > 4 h for HCl. A quantification was performed for propionic and acrylic acids following solvent desorption and gas chromatography. Both acids exhibited > 99% adsorption [the acid and its reactivity (the acid reacted with an indicator to contribute the color change)] on the pads at a spiking level of 1.8 microL for each acid. Acid recovery during quantification was calculated for each acid, ranging from 52-72% (RSD < or = 4.0%) for both acids over the spiking range 0.2-1.8 microL. The quantitative mass of the acids on the pads at the time of breakthrough detection ranged from 260-282 and 270-296 microg cm(-2) for propionic acid and acrylic acid, respectively. The new colorimetric indicator pad should be useful in detecting and collecting acid permeation samples through gloves and chemical protective clothing in both laboratory and field studies, for quantitative analysis.     

Synthesis of aliphatic polyesters by polycondensation using inorganic acid as catalyst

An effective route for the synthesis of aliphatic polyesters made from adipic or sebacic acid and alkanediols, using inorganic acid as a catalyst is reported. The monomer composition, reaction time, catalyst type, and reaction conditions were optimized to yield polyesters with weight average molecular weights of 23,000 for adipic acid and 85,000 for sebacic acid‐based polyesters. The polymers melt at temperatures of 52–65°C and possess melt viscosity in the range of 5600–19,400cP. This route represents an alternative method for producing aliphatic polyesters for possible use in the preparation of degradable disposable medical supplies. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of complexes pairing hydroperoxyl radical with peroxyformic acid

Ab initio quantum calculations are used to analyze the binding of complexes pairing OOH with HOOCHO. Six minima are located on the potential energy surface, all of cyclic geometry. Of particular interest are the OH...O and CH...O H-bonds that arise in the complexes and the manner in which these interactions influence the internal properties of the subunits. The analysis is complicated by the presence of an intramolecular H-bond in the unperturbed HOOCHO molecule, which must be broken in order to form the pair of intermolecular H-bonds that are responsible for the binding in the most stable complex. The CH bond of HOOCHO is contracted, and its stretching frequency undergoes a blue shift, when this group participates in a H-bond.     

Effect of inorganic ions on the photocatalytic degradation of humic acid

The article studies on the effects of six inorganic ions (Ca²⁺, Mg²⁺, Cl^?, SO ₄ ^2? , H₂PO ₄ ^? , and HCO ₃ ^? ) on titanium dioxide (TiO₂)-based photocatalytic degradation of humic acid (HA). We focus on the effects of the inorganic ions on HA characters, adsorption of HA on TiO₂ and photocatalytic degradation of HA. The results indicate that Ca²⁺ and Mg²⁺ with HA can form complexes which can decrease the solubility of HA, and then increase the HA adsorbed on TiO₂. However, the complex is more difficult to be degraded than HA. The effects of Cl^? and SO ₄ ^2? are closely related to their influences on HA solubility. The solubility changes of HA to some extent can enhance the adsorption of HA on TiO₂, and promote the photocatalytic degradation. Nevertheless, great solubility decreasing of HA can weaken the photocatalytic degradation. HCO ₃ ^? and H₂PO ₄ ^? can inhibit the photocatalytic degradation process seriously, because HCO ₃ ^? and H₂PO ₄ ^? are the strong scavengers of hydroxyl radicals, and can weaken the adsorption of HA on TiO₂ due to adsorption competition.     

Thermogravimetric and magnetic characteristics of some inorganic salts of dilituric acid

The thermolysis curves of the transition metal diliturates as well as those of copper, zinc, cadmium, ammonium and rubidium have been determined. These diliturates with the exception of ammonium and rubidium diliturates form hydrates. The oxides of the corresponding metals are obtained at relatively low temperatures. Magnetic susceptibility measurements show that these compounds are “essentially ionic” salts.     

A simple and efficient radical reduction using water-soluble radical initiator and hypophosphorous acid in aqueous alcohol

A simple, mild, and high-yielding procedure for the reduction of various halogenated compounds using a combination of the water-soluble radical initiator, 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (VA-061), a water-soluble chain carrier, hypophosphorous acid, and the base, triethylamine, in aqueous alcohol is described. The reagents used in this method are all water soluble, and therefore, an almost pure desired product can be readily obtained using only an extraction procedure.     

Amino acid derived heterocycles: lewis acid catalyzed and radical cyclizations from peptide acetals

Bicyclization of peptide acetals via nucleophilic attack of a phenyl group on an endocyclic acyliminium ion 4 was explored as a route to novel amino acid derived heterocycles and peptidomimetic scaffolds. In the presence of protic acid, bridged structures such as 6 are formed readily from phenylalanine derivatives, but the fused-ring analogues 5 could not be obtained in good yield. In contrast, radical cyclization of the bromophenyl dihydropyrazinone 7 provides an effective alternative for the synthesis of 5 (n = 0, 1, 2). Additional versatility in this process was demonstrated by efficient synthesis of a different fused ring system, represented by the antihelmintic praziquantel, 8.     

Steam chromatography with water—salt and water—acid inorganic phases

Th peculiarities of steam chromatography with water-salt and water-acid stationary liquid phases have been studied. The effects of the nature of the salt, its concentration in the stationary liquid phase, and the temperature of the column on retention values have been studied using C₁-C₈ primary nonbranched alcohols as an example. The advantages and disadvantages of steam chromatography with aqueous electrolyte phases arid challenges for the development of' this method are discussedTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1733–1739, July, 1996.