Spectrophotometric behavior of polyvinylpyrrolidone in aqueous and nonaqueous media (I)

Electronic spectral behavior of polyvinylpyrrolidone solutions in various media has been determined by UV-VIS spectrophotometry. A theoretical approach has been developed to explain the experimentally observed concentration dependent spectral behavior of polyvinyl pyrrolidone in aqueous and nonaqueous solvents. Increase in the concentration of the polymer or the addition of guanidine salts caused bathochromic shift. A similar concentration effect has been observed in nonaqueous media in the absence of guanidine salts.     

Potentiometric titration of peptides and the starting materials and intermediates of their synthesis. I. Acidimetric determination of N-acetylamino acids

The potentiometric titration of N-acetylamino acids and their sodium salts in nitromethane-acetic anhydride (2:1) with a nitromethane solution of perchloric acid has been investigated. A procedure has been developed for the quantitative determination of N-acetylamino acids in the presence of acetic acid in aqueous solutions. A differentiation determination of N-acetylamino acids and their salts in the presence of sodium acetate has been carried out.     

Cycloaddition of keteniminium with terminal alkynes toward cyclobuteniminium and their use in Diels–Alder reactions

An efficient access to cyclobutanone derivatives has been developed via a ‘one-pot’ [2+2]/[4+2] sequence involving keteniminium and cyclobuteniminium salts as key intermediates. A broad range of novel cyclobuteniminium salts have been prepared via [2+2] cycloaddition of keteniminium salts and alkynes. The resulting [2+2] adducts were then further transformed by Diels–Alder reaction with various dienes to afford cyclobutanone derivatives in good yields. A density functional theory (DFT) based computational study has been performed to obtain insight into the nature of the cycloaddition reactions and to investigate the difference in reactivity of cyclobuteniminium salts. Finally, the usefulness of cyclobutanone derivatives has been demonstrated by ring expansion reactions affording lactone, lactame, and cyclopentanone derivatives.     

Perfluoroalkanesulfonylimides and their lithium salts: synthesis and characterisation of intermediates and target compounds

ECF processes have been extensively experienced and developed since early 1970s at the Fluorine Chemistry Laboratory of Padua University: several classes of perfluorinated inert and functional compounds have been obtained, in particular perfluoro heterocyclics and perfluorinated acid fluorides.Recently the demand for electrolyte salts, applied in lithium batteries, drove our interest to investigate on the perfluoroalkanesulfonylimides.A series of the perfluoroalkanesulfonylfluoride precursors has been obtained by ECF and their metathesis to the related imides and lithium salts has been investigated.A number of representative products has been obtained and characterized in their structure and ionic conductivity.     

Further studies on the postpolymerization of methyl methacrylate

A search has been made for electroinitiators of postpolymerization. A number of hydroxycarboxylic acids and some of their sodium salts have been found to be quite efficient. Factors controlling the rate of polymerization and yield have been described. Surprisingly, citric acid, though not an electroinitiator of polymerization, is a good initiator of postpolymerization. Other active species that deserve mention are tartaric acid and its salts. A free radical mechanism involving formation of oligomeric initiator fragments, growth by attachment of imbibed monomer, and termination by chain transfer has been proposed to explain the observed facts.     

Supramolecular Synthons in Designing Low Molecular Mass Gelling Agents: L‐Amino Acid Methyl Ester Cinnamate Salts and their Anti‐Solvent‐Induced Instant Gelation

Easy access to a class of chiral gelators has been achieved by exploiting primary ammonium monocarboxylate ( PAM ), a supramolecular synthon. A combinatorial library comprising of 16 salts, derived from 5 l ‐amino acid methyl esters and 4 cinnamic acid derivatives, has been prepared and scanned for gelation. Remarkably, 14 out of 16 salts prepared (87.5 % of the salts) show moderate to good gelation abilities with various solvents, including commercial fuels, such as petrol. Anti‐solvent induced instant gelation at room temperature has been achieved in all the gelator salts, indicating that the gelation process is indeed an aborted crystallization phenomenon. Rheology, optical and scanning electron microscopy, small angle neutron scattering, and X‐ray powder diffraction have been used to characterize the gels. A structure‐property correlation has been attempted, based on these data, in addition to the single‐crystal structures of 5 gelator salts. Analysis of the FT‐IR and ¹H NMR spectroscopy data reveals that some of these salts can be used as supramolecular containers for the slow release of certain pest sex pheromones. The present study clearly demonstrates the merit of crystal engineering and the supramolecular synthon approach in designing new materials with multiple properties.     

Rational design, synthesis, and application of a new receptor for the molecular recognition of tricarboxylate salts in aqueous media

A rational design of a tripodal receptor for the molecular recognition of tricarboxylate salts in aqueous media, based on squaramide, has been performed using high-level DFT calculations (RI-BP86/SVP level of theory) in solution using the COSMO treatment, including some preliminary ab initio calculations at the higher RI-MP2/TZVP level of theory, comparing the ability of squaramide to bind carboxylate salts with two widely used guanidinium salts. The tripodal receptor has been synthesized using a new methodology that has been recently reported by some of us, and its capability of recognizing several mono-, di-, and tricarboxylate salts has been studied experimentally by means of microcalorimetry experiments in a very high competitive media, H(2)O:EtOH 1:3. These experiments give enthalpic and entropic data, which are unfortunately scarce in the literature of molecular recognition of anions. Finally, a fluorimetric ensemble of the receptor with fluorescein has been found to be useful for the fluorimetric determination of zinc citrate in a commercial toothpaste using competition assays.     

Synthesis of s-substituted derivatives of cyclic thionamides

A new preparative method for synthesizing S-substituted derivatives of cyclic thionamides by the cleavage of salts of thionamides with five-, six-, and seven-membered rings has been developed. It has been shown that the onium salts of the N-substituted derivatives of cyclic thionamides undergo cleavage at the C-S bond under the action of water or a weak base with the formation of N-substituted lactams and mercaptans.     

The azo coupling of 1-aryl quaternary salts of lepidine and quinaldine and some properties of the reaction products

A series of formazans has been obtained by the coupling of 1-aryllepidinium and 1-arylquinaldinium salts with diazonium salts. The formazans have been converted by oxidation into tetrazolium salts and by the action of acids into benzotriazines. The absorption spectra in the visible region have been measured in neutral, alkaline, and acid media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp. 1104–1111, August, 1970.     

Synthesis of pyrylium salts and pyridines containing heterocyclic substituents

A method of synthesizing pyrylium salts with heterocyclic substituents in the ring, has been investigated. The synthesis was carried out in two stages: alkaline condensation of aromatic and heterocyclic aldehydes with methyl ketones to give 1, 5-diketones, followed by cyclization to pyrylium salts by treatment with triphenylmethyl perchlorate. Pyridines containing heterocyclic substituents were obtained by treating the pyrylium salts with ammonia.     

4’-甲氧基-4-重氮二苯胺金属复盐稳定性的研究

本文研究了4′-甲氧基-4-重氮二苯胺(VB)金属复盐的稳定性,提出红外密度比值(D),热分解温度和光、热分解指数作为稳定性的量度。本文认为,4′-甲氧基-4-重氮二苯胺盐的分解为异裂反应。感光性能试验指出,感光胶片保存性参数与重氮盐稳定性参数之间有良好的相关性。     

A facile preparation of backbone-substituted, functionalized and chiral imidazolinium salts

A versatile and modular method for the preparation of various backbone-substituted, functionalized and chiral imidazolinium salts from the reaction of formamidines with alkene oxides has been described, providing a more straightforward access to substituted imidazolinium salts than the previously reported methods.     

Reaction of 1,4-benzoquinones with PH-phosphonium salts

A novel approach has been proposed to the synthesis of phosphonium salts containing a 1,4-dihydroxybenzo fragment via reaction of 2-methyl-1,4-benzoquinone or 2-isopropyl-5-methyl-1,4-benzoquinone with PH-phosphonium salts generated in situ from triphenylphosphine and trifluoromethanesulfonic or trifluoroacetic acid. The structure of the synthesized phosphonium salts was determined by NMR spectroscopy and X-ray analysis.     

ANTIBACTERIAL ACTIVITY OF SINGLE AND MIXED AMMONIUM AND PHOSPHONIUM SALTS GRAFTED ON "GEL-TYPE" STYRENE-DIVINYLBENZENE COPOLYMERS*

1.INTRODUCTIONThesynthesisofpolymer-supported"onium"salts(ammoniumandphosphonium)(1~5(wasdiscussedindetailduetothewidefieldofutilizationas:polarstationaryphasesforanionchromatography(6(,polymericreagentsfortrans-quaternizationreactions(7,8(,phase-transfercatalysts(9~13(andpolycationicbiocides(14~17(.Manychemicalmaterialssuchasozone,liquidchlorine,sodiumhydrochloride,s.a.,havebeenlargelyusedtosterilizeairandwater.Suchmaterialsrequirespecialequipmentandcarelessusemaycauseenvironmentalpolluti…     

First Synthesis of Thiophene Thioglycosides

A new method for the preparation of a new class of thiophene thioglycosides via one-pot reaction of the sodium thiophenethiolate salts with 2,3,4,6-tetra-O-acetyl-α-D-gluco- and galacto-pyranosyl bromides has been studied. The sodium thiophenethiolate salts are prepared using cyano-di-thioic analogs and their corresponding mono- and dithiolate salts.     

Correlation of crystal parameters with vibrational data of tetramethylammonium fluorocompounds

Examination of the solid state infrared spectra of the tetramethylammonium cation in ten salts shows correlation of infrared spectral properties with C-H…X hydrogen bonding and crystal habits in these tetramethylammonium salts. In this research a number of complexes of tetramethylammonium cation have been synthesized and the structures of five of them have been analyzed by X-ray single crystal diffraction. The IR predicted crystal habits are comprised by XRD data. The C-H stretching region characteristic hydrogen bonding shifts in the above salts. A good relation between two data has been found.     

Potentiometric titration of peptides and the starting materials and intermediates of their synthesis. I. Acidimetric determination of N-acetylamino acids

The potentiometric titration of N-acetylamino acids and their sodium salts in nitromethane-acetic anhydride (2:1) with a nitromethane solution of perchloric acid has been investigated. A procedure has been developed for the quantitative determination of N-acetylamino acids in the presence of acetic acid in aqueous solutions. A differentiation determination of N-acetylamino acids and their salts in the presence of sodium acetate has been carried out.All-Union Scientific-Research Institute of Applied Biochemistry, Biolar Scientific-Industrial Association, Olaine. Translated from Khimiya Prirodnykh Soedinenii, Vol. 6, pp. 830–834, November–December, 1989.     

Synthesis of 2-Methyl-4-quinolyl Isothiocyanate

A procedure has been developed for the synthesis of substituted 2-methylquinolin-4-ylthiuronium salts by reaction of 2-methyl-4-chloroquinoline with N-substituted thioureas. Alkaline hydrolysis of these salts yields 2-methyl-4-quinolyl isothiocyanate instead of the expected 2-methylquinoline-4-thiol.     

Crown ether-containing styryl dyes

The method for the synthesis of indoles from nitropyridinium salts has been improved. A method for synthesizing novel derivatives of indoleninium quaternary salts has been developed. The condensation of indoleninium salts with formyl derivatives of crown ethers leading to styryl dyes is described. Photoisomerization and complexing of crown-ether dyes with ions of alkaline and alkaline-earth metals have been studied. The shift of the long-wave absorption maximum has been observed to depend on the size and charge density of the metal cation.For communication 8, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1625–1632, September, 1993.     

Design and Synthesis of the First Thiophene Thioglycosides

A novel reported method for preparation of the first thiophene thioglycosides via a one-pot reaction of sodium thiophenethiolate salts with 2,3,4,6-tetra-O-acetyl-α-D-gluco- and galactopyranosyl bromides has been studied. The sodium thiophenethiolate salts were prepared using sodium cyanoethylene thiolate salts.