Search results for "Protonation"
showing 10 items of 583 documents
ChemInform Abstract: First Synthesis of the Chiral Mixed O/S Ligands, 1,2-Sulfinyl Thiols: Application as Chiral Proton Sources in Enantioselective P…
2001
Abstract A suitable method for the preparation of the chiral mixed O/S ligands 1,2-sulfinyl thiols is described. These compounds have then been used as a chiral proton source in the enantioselective protonation of 2-methyl tetralone enolate and the results are compared with those obtained from the analogous alcohols. A theoretical model is proposed to explain the different behaviors exhibited in the protonation reaction for each of these proton sources. Configurational assignments for the new chiral thiols have been carried out by means of X-ray analysis.
Diaryldistyrylpyrazines: Solvatochromic and Acidochromic Fluorophores
2013
Diaryldimethylpyrazines are the starting materials for the synthesis of C2-symmetric donor- or acceptor-substituted distyrylpyrazines. The optical properties of these cruciform-shaped dyes are dominated by the distyrylpyrazine units; the photophysics is controlled by the styryl substitution, the diaryl substituents on the central pyrazine only having a small effect. Protonation occurs on the pyrazine and/or lateral amines or azines, thereby altering the absorption and emission properties. Hypso- and bathochromism as well as fluorescence quenching depend on the nature of the terminal substituent. This, and a significant positive solvatochromism of the fluorescence, allow optical sensing of t…
Herbicidal Derivatives of Aminomethylenebisphosphonic Acid. Part IV. Hydroxyalkylidenebisphosphonates, Iminomethylenebisphosphonates and Ureidomethyl…
2000
Derivatives of aminomethylenebisphosphonic acids constitute a class of promising herbicides. Replacement of the amino group by hydroxyl, ureido, thioureido, or imino moieties leads to compounds of significant herbicidal properties. This indicates that protonated amino function is not a requirement for phytotoxic action of bisphosphonates.
Uranium( iv ) cyclobutadienyl sandwich compounds: synthesis, structure and chemical bonding
2019
The 1 : 1 reactions of uranium(IV) tetrakis(borohydride) with the sodium and potassium salts of the cyclobutadienyl anion [C4(SiMe3)4]2− (Cb′′′′) produce the half-sandwich complexes [Na(12-crown-4)2][U(η4-Cb′′′′)(BH4)3] and [U(η4-Cb′′′′)(μ-BH4)3{K(THF)2}]2. In the 1 : 2 reaction of U(BH4)4 with Na2Cb′′′′, formation of [U(η4-Cb′′′′)(η3-C4H(SiMe3)3-κ-(CH2SiMe2)(BH4))]− reveals that a Cb′′′′ ligand undergoes an intramolecular deprotonation, resulting in an allyl/tuck-in bonding mode. A computational study reveals that the uranium–Cb′′′′ bonding has an appreciable covalent component with contributions from the uranium 5f and 6d orbitals. peerReviewed
meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species
2015
Susceptibility to interact with trifluoroacetic acid (TFA) of selected free-base porphyrins, including a novel lipophilic 3-n-pentadecyl(phenoxy)-ethoxy-phenyl-substituted porphyrin, and photostability of their diprotonated compounds was explored in benzene and N,N-dimethylformamide (DMF). Results have been discussed in terms of the commonly applied pK a -based procedure and confronted with a simple approach derived from experimentally-determined correlations reflecting the porphyrins affinity for TFA. Density functional theory (DFT) has proved the porphyrin moiety creates stable diprotonated species involving two TFA molecules, in which the fluorine atoms effectively contribute to the over…
Synthèse et étude physico-chimique de ligands macrocycliques, macrobicycliques et macrotricycliques dérivés du 5,12-dioxocyclame
2002
The synthesis and the physico-chemical studies of macropolycyclic ligands based on 5,12-dioxocyclam L1 are presented. The first part of this dissertation presents the structural and physico-chemical properties of L1 and its N-substituted derivatives L2 and L3. A potentiometric study reveald a cooperative protonation of the two macrocyclic ligands L1 and L2 whereas the study of the macrotricycle L3 in a methanol-water mixture revealed a sequential cooperative diprotonation of the four tertiary amines. The square planar nickel and copper complexes were synthesized and characterized using infrared, UV-vis and ESR spectgroscopy. The spectroscopic studies showed the presence of intermolecular hy…
2,2′-Bipyridin-1-ium hemioxalate oxalic acid monohydrate
2018
The asymmetric unit of the title compound, C10H9N2 +·0.5C2O4 2−·C2H2O4·H2O, consists of a 2,2′-bipyridinium cation, half an oxalate dianion, one oxalic acid and one water molecule. One N atom in 2,2′-bipyridine is unprotonated, while the second is protonated and forms an N—H...O hydrogen bond. In the crystal, the anions are connected with surrounding acid molecules and water molecules by strong near-linear O—H...O hydrogen bonds. The water molecules are located between the anions and oxalic acids; their O atoms participate as donors and acceptors, respectively, in O—H...O hydrogen bonds, which form sheets arranged parallel to the ac plane.
6-Amino-2-iminiumyl-4-oxo-1,2,3,4-tetrahydropyrimidin-5-aminium sulfate monohydrate
2019
The title compound, C4H9N5O2+·SO4 2−·H2O, is the monohydrate of the commercially available compound `C4H7N5O·H2SO4·xH2O'. It is obtained by reprecipitation of C4H7N5O·H2SO4·xH2O from dilute sodium hydroxide solution with dilute sulfuric acid. The crystal structure of anhydrous 2,4,5-triamino-1,6-dihydropyrimidin-6-one sulfate is known, although called by the authors 5-amminium-6-amino-isocytosinium sulfate [Bieri et al. (1993). Private communication (refcode HACDEU). CCDC, Cambridge, England]. In the structure, the sulfate group is deprotonated, whereas one of the amino groups is protonated (R 2C—NH3 +) and one is rearranged to a protonated imine group (R 2C=NH2 +). This arrangement is very…
4,4′-(1,2-Diazaniumylethane-1,2-diyl)dibenzoate trihydrate
2016
The title compound, C16H16N2O4·3H2O, was synthesized from (1R,2R)-1,2-bis(2-hydroxyphenyl)ethylenediamine and terephthalaldehydic acid. The compound crystallizes from water as a double zwitterion with protonated amine groups and deprotonated carboxylate groups. The dihedral angle formed by the aromatic rings is 3.86 (11)°. In the crystal, N—H...O and O—H...O hydrogen bonds link molecules into a three-dimensional network.
N-(6-Methylpyridin-2-yl)mesitylenesulfonamide and acetic acid--a salt, a cocrystal or both?
2015
In the solid obtained fromN-(6-methylpyridin-2-yl)mesitylenesulfonamide and acetic acid, the constituents interactviatwo N—H...O hydrogen bonds. The H atom situated in one of these short contacts is disordered over two positions: one of these positions is formally associated with an adduct of the neutral sulfonamide molecule and the neutral acetic acid molecule, and corresponds to a cocrystal, while the alternative site is associated with salt formation between a protonated sulfonamide molecule and deprotonated acetic acid molecule. Site-occupancy refinements and electron densities from difference Fourier maps suggest a trend with temperature, albeit of limited significance; the cocrystal i…