Copolymer of N,N-diallyl-N,N-dimethylammonium chloride with sulfur dioxide as carrier of drugs

Immobilization of drugs on macromolecules of copolymer N,N-diallyl-N,N-dimethylammonium chloride with sulfur dioxide using ion exchange technique was investigated. Ways of producing polymer-drug conjugates of preset compositions were developed. Their structure was found by NMR and IR spectroscopy.     

Computational and experimental approaches to the molecular structure of the HCl adduct of Me3PO

The reaction of anhydrous HCl_(g) with trimethyl phosphane oxide yields trimethylhydroxy phosphonium chloride. A crystal structure analysis showed that the prevalent mesomeric structure in the solid state is the phosphonium chloride ion pair. Ab initio calculations in the gas phase cannot reproduce these findings, whereas higher correlated methods (CISD) and solvation models predict the experimental structure correctly.     

Coulometric titration with electrogenerated +2 tin: Determination of iodine,bromine, and various oxidants via iodometry

The use of electrolytically generated +2 tin as a coulometric titrant has been studied. In a 3 to 4M sodium bromide and 0.2N hydrochloric acid solution, containing 0.2M stannie chloride, the generation of stannous ion is 100% efficient up to a current density of 80 mA/cm². With this medium iodine and bromine can be titrated coulometrically with errors of about ±0.3% or less. The titration is well suited for the iodometric determination of strong oxidants. Employing stannous ion and bromine for direct and reverse titrations, quinone and hydroquinone have been titrated.     

MALDI-MS/MS with Traveling Wave Ion Mobility for the Structural Analysis of N-Linked Glycans

The preference for singly charged ion formation by MALDI makes it a better choice than electrospray ionization for profiling mixtures of N-glycans. For structural analysis, fragmentation of negative ions often yields more informative spectra than fragmentation of positive ones but such ions are more difficult to produce from neutral glycans under MALDI conditions. This work investigates conditions for the formation of both positive and negative ions by MALDI from N-linked glycans released from glycoproteins and their subsequent MS/MS and ion mobility behaviour. 2,4,6-Trihydroxyacetophenone (THAP) doped with ammonium nitrate was found to give optimal ion yields in negative ion mode. Ammonium chloride or phosphate also yielded prominent adducts but anionic carbohydrates such as sulfated N-glycans tended to ionize preferentially. Carbohydrates adducted with all three adducts (phosphate, chloride, and nitrate) produced good negative ion CID spectra but those adducted with iodide and sulfate did not yield fragment ions although they gave stronger signals. Fragmentation paralleled that seen following electrospray ionization providing superior spectra than could be obtained by PSD on MALDI-TOF instruments or with ion traps. In addition, ion mobility drift times of the adducted glycans and the ability of this technique to separate isomers also mirrored those obtained following ESI sample introduction. Ion mobility also allowed profiles to be obtained from samples whose MALDI spectra showed no evidence of such ions allowing the technique to be used in conditions where sample amounts were limiting. The method was applied to N-glycans released from the recombinant human immunodeficiency virus glycoprotein, gp120.     

Addition of chlorine,bromine and bromine chloride to some α,β-unsaturated methyl esters

The additions of chlorine, bromine and bromine chloride to trans methyl 2-butenoate 1, trans methyl 2-methyl-2-butenoate 2 and methyl 3-methyl-2-butenoate 3 under ionic conditions were studied. Bromine chloride addition always gave as a major regioisomer the 2-bromo-3--chloro compound,almost quantitatively in the case of 3. The mechanism of bromonium ion ring-opening (S_N1 or S_N2) is discussed with respect to the double bond substitution and regioisomer proportions. The dihalo products were identified by MS, ¹H and ¹³C NMR.     

Electrochemical oxidation of barbituric acids at low pH in the presence of chloride ion

Barbituric acid, 1-methylbarbituric acid and 1,3-dimethylbarbituric acid are electrochemically oxidized at the pyrolytic graphite electrode by way of a single voltammetric peak at pH 1 in the presence of chloride ion. At least four products are formed as a result of the reaction, the three major products, accounting for more than 80–90% of the oxidized barbituric acid, are the appropriately N-methylated 5,5′-dichlorohydurilic acids, 5,5-dichlorobarbituric acids and alloxans. The mechanism appears to proceed by an initial potential-controlling 1e/1H⁺ oxidation of the barbituric acids to give a barbituric acid radical. This can dimerize to hydurilic acid, which is then further electrochemically oxidized. However, this appears to be a minor route. The barbituric acid radical appears to be mainly further electrooxidized (1e) to a carbonium ion which further reacts with nucleophiles such as chloride ion to give 5-chlorobarbituric acid, or with water to give dialuric acid. Further electrochemical oxidation and chemical reactions of the latter species results in formation of the ultimate products.     

Investigation of ion pair formation in the triphenylmethyl chloride–trimethyl aluminium system,as a model for the activation of olefin polymerization catalyst

Triphenylmethyl chloride (“trityl chloride”, Ph₃CCl) will transfer chloride ions to aluminium alkyls and methylaluminoxane and it is thereby converted into 1,1,1-triphenylethane (“trityl methyl” Ph₃CMe) and the triphenylcarbonium ion (“trityl ion”, Ph₃C⁺). IR spectra of these trityl species have been recorded. Assignments are supported by quantum chemical calculations, leading to significant revisions for some of the modes that are most influenced by reactions. A bright yellow colour shown to be due to the trityl cation, makes trityl chloride a useful indicator for ion pair formation. Trimethyl aluminium (TMA) is chlorinated by trityl chloride and forms dimethyl aluminium chloride (DMAC). DMAC will form a stable ion pair with trityl chloride, probably by forming the anion Al₂Cl₃Me₄⁻. Large excess of trityl chloride causes the formation of AlCl₄⁻, and probably AlCl₃Me⁻ and AlCl₂Me₂⁻ anions. It appears that methyl aluminium chloride anions are formed if, and only if, the anions have at least three chlorine atoms, possibly because of the need to dissipate the negative charge enough to keep the anion dissolved in the hydrocarbon solvent. Methylaluminoxane (MAO) also forms ion pair with trityl chloride, although to lesser extent and less persistent.     

Extraction and separation of gallium, indium and thallium with several carboxylic acids from chloride media

A method is proposed for the extraction and individual separation of trivalent gallium, indium and thallium with sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100) and naphthenic acid (NA) from chloride media. The distribution equilibria of gallium (III), indium (III), thallium (III) and thallium (I) between carboxylic acids (CA-12, CA-100 and NA) dissolved in kerosene and acidic aqueous chloride media has been investigated as a function of the concentration of extractants and the concentration of hydrogen ion in aqueous phase. A possible mechanism of the extraction is discussed. The method permits rapid and precise individual separation of gallium (III), indium (III) and thallium (III), and is applicable to the analysis of alloy samples.     

Selective reduction of tertiary alkyl,benzyl, and allyl halides to hydrocarbons using lithium 9,9-di-n-butyl-9-borabicyclo[3.3.1]nonanate

The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation.     

Ring opening of 2-acylaziridines by acid chlorides

Good nucleophilicity of the ring nitrogen in chiral (2R,1′R)-2-acyl-(1′-phenylethyl)aziridines initiated the reaction with various acid chlorides to form the corresponding acylaziridinium ion intermediates whose rings were opened by the chloride anion to yield the β-amino-α-chlorocarbonyl compounds. The subsequent displacement of the chloride with the internal oxygen nucleophile originated from methylchloroformate, acetyl chloride, and methyl chlorooxoacetate yielded oxazolidin-2-ones, β-amino-α-acetyloxypropionates, and morpholin-2,3-diones, respectively.     

An approach to total synthesis of the cylindricine B pyridoquinoline subclass of tricyclic marine ascidian alkaloids

Employing an intramolecular N-acylketiminium ion/olefin hetero Diels-Alder reaction, and a ring closing metathesis of a vinyl chloride as pivotal steps, it is possible to directly access the pyridoquinoline tricyclic ring system of the marine alkaloids cylindrines B and J.     

Theoretical Van 't Hoff plots of gas-phase ion equilibria of chloride ion in water,methanol and acetonitrile

The gas-phase clustering reactions of chloride ion with water, methanol and acetonitrile molecules were investigated using a pulsed e-beam high-pressure mass spectrometer. Thermochemical data, −ΔH⁰ and −ΔS⁰, for these reactions agree with those reported previously. Theoretical van 't Hoff plots based on an ab initio MO calculation are compared with experimental ones.     

The reaction of metalloporphyrins with nitrogen dioxide

The octaethylporphyrin(OEP) complexes of iron(III) chloride, iron(III) acetate, thallium(III) hydroxide, zinc(II), and cobalt(II) and the mesoporphyrin IX dimethyl ester (MPDME) complexes of zinc(II) and iron(III) chloride were reacted with a 20:1 ratio of NO₂ to metalloporphyrin in CH₂Cl₂. The +3 metalloporphyrins gave products which had a nitromethyl group in each of the four meso positions of the porphyrin ring and a chloride ion bound to the metal atom. The products of +2 metalloporphyrin reaction had a nitro group bound in each of the meso positions. The spectral and electrochemical properties of some of the products were measured. ³⁶Cl labelled OEPFeCl was reacted with NO₂ in CH₂Cl₂. The product, meso-tetranitromethyl OEPFeCl, had 17% of the original activity which indicates that the chloride ion bound to the iron is exchanged with chloride ions formed in the reaction. The nitromethylation reaction appears to involve initially the displacement of chloride from iron(III) by NO₂ and solvent attack on the bound NO₂. The meso-nitration of the +2 metalloporphyrin by NO₂ has been proposed to proceed by a π-cation radical mechanism (E.C. Johnson and D. Dolphin, TetrahedronLetters 2197 (1976).     

Oxidation of organic compounds by tervalent manganese compounds: IX. Determination of the titer of hexaquomanganese(III) ion standard solutions in perchloric acid

Optimum conditions have been found for the determination of the titer of 0.005 N solutions of hexaquomanganese(III) ion by potentiometric titration of ferrous chloride. The accuracy and reproducibility of this method were studied. A new method of determining the titer of dilute solutions of hexaquomanganese(III) ion has been proposed, using potassium iodide as a primary standard. The optimum conditions for this titration have been found and its applicability to the determination of the titer of 0.005, 0.001, and 0.0005 N solutions has been verified.     

5-Arylthiopyrimidine, 1. Mitt.: Cyclisierung von 4-Carboxyderivaten zu 10H-[1]Benzothiopyrano[3,2—d]pyrimidin-10-onen

Potassium 2-methylthio-5-bromopyrimidine-4-carboxylate was condensed with thiophenoxide ion containing various electron releasing groups to produce 2-methylthio-5-arylthiopyrimidine 4-carboxylic acids. Some of these acids were cyclized through their acid chlorides with anhydrous aluminum chloride to their corresponding 10H-[1]benzothiopyrano[3.2—d]pyrimidin-10-ones.     

New development in the enantioselective ring opening of meso-epoxides by various chloride ion silicon sources catalyzed by an o-methoxyaryldiazaphosphonamide Lewis base

New developments in the enantioselective ring opening of meso-epoxides catalyzed by a chiral Lewis base have been achieved using various chloride ion silicon sources. Thus, the use of TMSCl led to enantioselectivities varying from 6 to 98% ee depending on the nature of the considered epoxide.     

Solubility and physic-chemical properties of NaH2PO4 in phosphoric acid,sodium chloride and their mixture solutions at T = (298.15 and 313.15) K

In this study, solubility and physic-chemical properties of sodium dihydrogen phosphate in sodium chloride, phosphoric acid and their mixture solutions at T = (298.15 and 313.15) K have been investigated by using isothermal dissolution method. In the three systems, the solubility of NaH₂PO₄ always increases with the temperature increasing and decreases with molar concentration of phosphoric acid (sodium chloride) increasing because of the same ion effect. Solubility data of sodium dihydrogen phosphate in the mixed solution of sodium chloride and phosphoric acid is basically required for designing and optimizing the solvent extraction process in the industrial production.     

A single point mutation converts a proton-pumping rhodopsin into a red-shifted,turn-on fluorescent sensor for chloride

The visualization of chloride in living cells with fluorescent sensors is linked to our ability to design hosts that can overcome the energetic penalty of desolvation to bind chloride in water. Fluorescent proteins can be used as biological supramolecular hosts to address this fundamental challenge. Here, we showcase the power of protein engineering to convert the fluorescent proton-pumping rhodopsin GR from Gloeobacter violaceus into GR1, a red-shifted, turn-on fluorescent sensor for chloride in detergent micelles and in live Escherichia coli. This non-natural function was unlocked by mutating D121, which serves as the counterion to the protonated retinylidene Schiff base chromophore. Substitution from aspartate to valine at this position (D121V) creates a binding site for chloride. The binding of chloride tunes the pK_a of the chromophore towards the protonated, fluorescent state to generate a pH-dependent response. Moreover, ion pumping assays combined with bulk fluorescence and single-cell fluorescence microscopy experiments with E. coli, expressing a GR1 fusion with a cyan fluorescent protein, show that GR1 does not pump ions nor sense membrane potential but instead provides a reversible, ratiometric readout of changes in extracellular chloride at the membrane. This discovery sets the stage to use natural and laboratory-guided evolution to build a family of rhodopsin-based fluorescent chloride sensors with improved properties for cellular applications and learn how proteins can evolve and adapt to bind anions in water.

By utilizing laboratory-guided evolution, we have converted the fluorescent proton-pumping rhodopsin GR from Gloeobacter violaceus into GR1, a red-shifted, turn-on fluorescent sensor for chloride.     

Vergleich von anionenanalysenergebnissen aus der bestimmung mittels ionenchromatographie und klassischen analysenmethoden

(Comparison of analytical results for common anions obtained by ion chromatography and classical methods.)The concentrations of chloride, nitrate, and sulphate were determined in ground-water samples by ion chromatography and by the classical titrimetric, photometric, and gravimetric methods. The results were compared by an orthogonal regression procedure. The criteria established and the tests of the confidence intervals of the orthogonal regression function indicate that the results obtained by the different analytical methods are similar for chloride and sulphate but not for nitrate.     

Design of steroid-based imidazolium receptors for fluoride ion recognition

New deoxycholic acid-based cyclic receptors bearing imidazolium and benzimidazolium moieties bridged with o-xylelene and 1,8-dimethylenenaphthalene groups have been synthesized. Anion binding studies using ¹H NMR revealed that receptors having naphthalenic group as spacer exhibit very high selectivity for fluoride ion over other anions while receptors with o-xylelene group show a preference for the chloride ion.