Search results for "ammonium"
showing 10 items of 1070 documents
The Synergetic Interplay of Weak Interactions in the Ion-Pair Recognition of Quaternary and Diquaternary Ammonium Salts by Halogenated Resorcinarenes
2013
The influence of halogens on the noncovalent interactions of different upper-rim-substituted hexylresorcinarenes with quaternary and diquaternary ammonium iodide salts was investigated in the gas phase by electrospray ionization Fourier-transform ion-cyclotron-resonance (ESI-FTICR) mass spectrometry and in solution by 1H NMR titration studies. The electronic nature of the substituents on the upper rim of the resorcinarene was directly reflected in the order of binding strengths of the hosts towards quaternary and diquaternary ammonium cations in the gas phase. In solution, the opposite trend was observed, with generally higher binding constants for the diquaternary over the quaternary salts…
C-Methyl resorcin[4]arene packing motifs with alkyl ammonium salts: From molecular capsules to channels and tubes
2005
A variety of packing motifs of C-methyl resorcinarene were obtained when complexed with small alkyl ammonium salts of different size and shape. Using bromide and chloride salts of the small quaternary alkyl ammonium cations, tetramethyl ammonium and dimethyldiethyl ammonium, leads to a grid-like packing of solvent mediated dimeric capsules while the use of salts of larger diquaternary cations bearing a 1,4-diazabicyclo[2.2.2]octane (DABCO) scaffold produces solvent/anion mediated chains and channels or tubular structures. The connecting interactions between resorcinarenes in each structure are hydrogen bonding and/or π⋯π interactions.
Self-assembling resorcinarene capsules: solid and gas phase studies on encapsulation of small alkyl ammonium cations
2002
The self-assembling process of unsubstituted resorcinarenes (1, 2 and 3) to dimeric capsules encapsulating small tetra-alkyl ammonium cations 4–7 has been studied in solid and gaseous states by X-ray crystallographic and mass spectrometric methods. Hydrogen bonding and cation-π interaction as well as the proper encapsulation in the empty cavity of the capsule appear to be the most important interactions in the capsule formation process. Competitive mass spectrometric studies clearly indicated preference of the tetramethyl ammonium cation (4) over tetraethyl ammonium cation (6) and especially tetrabutyl ammonium cation (7). The crystal structures of altogether eight dimeric capsules of resor…
Recognition of N-Alkyl- and N-Aryl-Acetamides by N-Alkyl Ammonium Resorcinarene Chlorides
2014
N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and intermolecular hydrogen bonds that leads to cavitand-like structures. Depending on the upper-rim substituents, self-inclusion was observed in solution and in the solid state. The self-inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self-included dimers spontaneously reorganize to 1:1 host-guest complexes. These host compounds show an interesting ability to bind a series of N-alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C=O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl(-)) and ammoni…
The thermal decomposition, IR spectrum and crystal structure of ammonium manganese(II) tris(hydrogenselenite), NH4Mn(HSeO3)3
1985
Abstract The compound NH 4 Mn(HSeO 3 ) 3 has been prepared and its IR spectrum and thermal behaviour have been investigated. It crystallizes in the monoc
Novel one-pot synthesis of quaternary ammonium halides: new route to ionic liquids
2004
Treatment of an amide with an alkyl or substituted alkyl halide in the presence of a weak base in a one-pot reaction leads to crystalline quaternary ammonium halides with reasonable chemical yields; some of the compounds show low melting points and a liquid range of over 50–100 °C before decomposition.
Studien zum Vorgang der Wasserstoffübertragung, 73. Die Reduktion prochiraler Alkyl(aryl)ketone zu Carbinolen und Pinakolen mit Alkaliamalgamen
1984
Es werden die Faktoren ermittelt, welche die Stereochemie und das Mengenverhaltnis (C/P) des bei der Reduktion von Acetophenon mit Lithium-, Natrium- und Kaliumamalgam (Li/Hg, Na/Hg, K/Hg) gebildeten Carbinols (C) und Pinakols (P) bestimmen. Das C/P-Verhaltnis wird beeinflust a) durch Protonendonatoren, b) durch quartaren Ammoniumsalze, c) durch bis-tertiare Amine. Bei Anwesenheit von optisch aktiven quartaren Ammoniumsalzen und optisch aktiven bis-tertiaren Aminen wird sowohl beim Pinakol als auch beim Carbinol eine geringe optische Induktion beobachtet. Bei der Reduktion von Pivalophenon mit Li/Hg entsteht das anomale Dimerisierungsprodukt 20. Studies on the Occurrence of Hydrogen Transfe…
Bimodal Effect of Amphiphilic Biocide Concentrations on Fluidity of Lipid Membranes
1996
Abstract Using the spin label method (ESR) it has been shown that biologically active, amphiphilic compounds (quaternary ammonium salts -AS) containing polar heads with single and double positive charge caused, at low concentrations, decrease fluidity of liposome membranes formed with egg yolk lecithin (EYL). At higher concentrations an increase in fluidity was observed. With compounds having a single positive charge minimum fluidity of membrane structure occurs in the range of 1 to 3%, with compounds containing double positive charge -in the range of 4 -6 % . That effect does not depend on polar head size and length of alkyl chains of the AS used. Analysis of the electrostatic interaction …
Cellulose Nanocrystals from Lignocellulosic Raw Materials, for Oxygen Barrier Coatings on Food Packaging Films
2017
Cellulose nanocrystals (CNCs) are unique, renewable top-down nano particles from which coatings with improved gas barrier properties and new functionalities can be prepared. In this paper, the potential for obtaining such high performing nanocrystals from low-cost lignocellulosic by-products or raw materials is proved by a comparison study on CNCs obtained both from cotton linters and kraft pulp, by means of the ammonium persulfate (APS) process. Morphological and chemical characterization of the nanocrystals obtained, as well as the main functional properties of the poly(ethylene terephthalate) coated films, showed quite similar characteristics and performances of CNCs obtained from pure c…
A five-step synthesis of (±)-tylophorine via a nitrile-stabilized ammonium ylide.
2012
The Stevens rearrangement of a nitrile-stabilized ammonium ylide is the key step of a very short and practical synthesis of the phenanthroindolizine alkaloid (±)-tylophorine. The method requires only five linear steps and is devoid of any protecting group manipulations.