Ligand scrambling reactions of cyano(thione)gold(I) complexes and determination of their equilibrium constants

2002 ◽  
Vol 80 (10) ◽  
pp. 1279-1284 ◽  
Author(s):  
Saeed Ahmad ◽  
Anvarhusein A Isab ◽  
Herman P Perzanowski
Keyword(s):  
Ionic Strength ◽  
Nmr Spectroscopy ◽  
Key Words ◽  
Equilibrium Constants ◽  
Solvent Polarity ◽  
Approach To Equilibrium ◽  
Initial Concentration ◽  
C Nmr

Ligand scrambling reactions in cyano(thione)gold(I) complexes ([>C=S-Au-CN]) to form [Au(>C=S)2]+ and [Au(CN)2]– species have been investigated for a series of thiones in DMSO using 13C and 15N NMR spectroscopy. Rapid approach to equilibrium occurred and resulted in distinct signals for the [>C=S-Au-CN] and [Au(CN)2]– complexes, both in 13C and 15N NMR. Equilibrium constants (Keq) were determined for scrambling of all the complexes by integrating the CN resonances in the 13C NMR recorded at 298 K. The influence of various factors (initial concentration, ionic strength, temperature, and solvent polarity) on the Keq value was examined for a representative complex (ImtAuCN (Imt = Imidazolidine-2-thione)).Key words: cyanogold(I) complexes, thiones, ligand scrambling, NMR, Keq.

Determination of petroselinic acid inUmbelliflorae seed oils by combined GC and13 C NMR spectroscopy analysis

1990 ◽  
Vol 67 (10) ◽  
pp. 607-610 ◽  
Author(s):  
J. F. Mallet ◽  
E. M. Gaydou ◽  
A. Archavlis
Keyword(s):  
Nmr Spectroscopy ◽  
Petroselinic Acid ◽  
Seed Oils ◽  
Spectroscopy Analysis ◽  
C Nmr

Strukturermittlung der Reduktionsprodukte von Pyridostigmin mit NaBH4 / Determination of the Structure of Products of the Reduction of Pyridostigmine with NaBH4

1985 ◽  
Vol 40 (10) ◽  
pp. 1401-1408
Author(s):  
Volker Horstmann ◽  
Günter Häfelinger
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Structure ◽  
Main Product ◽  
Reaction Conditions ◽  
C Nmr

The chemical structure of 5 different products of pyridostigmine obtained by reduction with NaBH4 was determined by GC-MS and subsequently confirmed by means of 1H and 13C NMR spectroscopy. Reaction conditions leading almost exclusively to the main product: 3-[(N,N-dimethyl)-carbamoyl]-1-m ethyl-1,2,5,6-tetrahydropyridine (4) have been determined.

Solution carbocation stabilities measured by internal competition for a hydride ion

1982 ◽  
Vol 60 (17) ◽  
pp. 2180-2193 ◽  
Author(s):  
Nancy E. Okazawa ◽  
Ted S. Sorensen
Keyword(s):  
Nmr Spectroscopy ◽  
Equilibrium Constants ◽  
Analytical Tool ◽  
Steric Interactions ◽  
Hydride Ion ◽  
Methylene Chain ◽  
Internal Competition ◽  
Equilibration Process ◽  
Better Than ◽  
C Nmr

Although many techniques are known which allow one to compare the stabilities of solution carbocations, that involving the intermolecular competition for a hydride ion is conceptually (but not experimentally) the simplest procedure. This paper describes a variant of this which is experimentally more reliable and which uses intramolecular equilibria where the two competing systems are held together by a —(CH2)n— chain, e.g.[Formula: see text]By systematically varying "n" in this example (n = 0, 1,2, or 3), it has been found that a methylene chain of two or more carbons is necessary in order to minimize steric interactions between the end "systems". It has also been found that all cycloalkyl rings studied (except cyclohexyl) stabilize a cation centre much better than an aliphatic equivalent, i.e. [Formula: see text], in agreement with solvolysis rate studies. The same situation was found when comparing this aliphatic "system" against the 2-norbornyl cation (bicyclic) or against the tricyclic 2-adamantyl cation. In fact, in these cases the equilibria are too lop-sided to obtain numerical values for the equilibrium constants concerned. Finally, three carbocations were looked at where the 2-norbornyl cation structure was pitted against the structurally very related cyclopentyl, bicyclo[2.1.1]hexyl, and bicyclo[3.2.1]octyl cations. In all cases, the 2-norbornyl cation is the more stable. 13C nmr spectroscopy was used as the analytical tool to measure (or attempt to measure) the equilibrium constants. Depending on the rate of the equilibration process, three different techniques are involved and the relative merits of these are discussed in the latter part of the paper.

Notizen: Einfache Bestimmung der Substituentenposition im Pyrrolring von Pyrrolo[2,3-d] Pyrimidinen und 7-Desazapurinnucleosiden durch 13C-NMR / Simple Determination of the Position of Substitution in the Pyrrol Ring of Pyrrolo[2,3-d]pyrimidines and 7-Deazanucleosides Using 13C NMR

1977 ◽  
Vol 32 (8) ◽  
pp. 958-960 ◽  
Author(s):  
Uwe Lüpke ◽  
Frank Seela
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Side Chains ◽  
C Nmr

The position of substituents at C-5 or C-6 of pyrrolo[2,3-d]pyrimidines can be determined by 13C NMR spectroscopy. The method can also be used for 7-deazanucleosides and allows the assignment of the position of side chains.

Identification and quantitative determination of carbohydrate molecules in Greek honey by employing 13C NMR spectroscopy

2015 ◽  
Vol 7 (14) ◽  
pp. 5962-5972 ◽  
Author(s):  
Aristea Kazalaki ◽  
Maria Misiak ◽  
Apostolos Spyros ◽  
Photis Dais
Keyword(s):  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
C Nmr

A methodology based on 13C NMR spectroscopy was employed to detect and quantify fourteen mono-, di- and trisaccharide molecules in authentic Greek honey samples with no prior separation.

Oxidative fluorination in the Ph2SO–XeF2–Cl− system and fluorine exchange in the Ph2S(O)F2–Ph2S(O)F+ system

1996 ◽  
Vol 74 (11) ◽  
pp. 2002-2007 ◽  
Author(s):  
Xiaobo Ou ◽  
Alexander F. Janzen
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio ◽  
Key Words ◽  
Exchange Process ◽  
Chloride Ion ◽  
Fluoride Ion ◽  
Molecular Orbital Calculations ◽  
Xenon Difluoride ◽  
Mild Conditions ◽  
C Nmr

Oxidative fluorination of diphenyl sulfoxide with xenon difluoride occurs under mild conditions in the presence of chloride ion to give Ph2S(O)F2 in quantitative yield. Chloride ion appears to react with xenon difluoride to generate fluoride ion, and a mechanism of oxidative fluorination is proposed that involves anionic Ph2S(O)F− and radical Ph2S(O)F• intermediates. Addition of cationic Ph2S(O)F+ to Ph2S(O)F2 initiates rapid fluorine exchange, presumably via a symmetrical fluorine-bridged intermediate, and this exchange process was monitored by 13C and 19F NMR spectroscopy. In the presence of chloride ion, Ph2S(O)Cl2 is formed and can be identified by 13C NMR and by its hydrolysis to Ph2SO2. Mechanisms are proposed for these reactions, and ab initio molecular orbital calculations (GAUSSIAN92) were carried out of the postulated intermediates. Key words: preparation of Ph2S(O)F2, Ph2S(O)F+, and Ph2S(O)Cl2; oxidative fluorination in the Ph2SO–XeF2–Cl− system; fluorine exchange in the Ph2S(O)F2–Ph2S(O)F+ system.

scholarly journals Determination of malate‐aspartate shuttle activity in intact hearts using 13 C NMR spectroscopy and modeling

2009 ◽  
Vol 23 (S1) ◽  
Author(s):  
Ming Lu ◽  
Gerald Saidel ◽  
Xin Yu
Keyword(s):  
Nmr Spectroscopy ◽  
Malate Aspartate Shuttle ◽  
C Nmr

scholarly journals Protolytic equilibria in homogeneous and heterogeneous systems of ketoconazole and its direct spectrophotometric determination in tablets

2005 ◽  
Vol 70 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Mirjana Vojic ◽  
Gordana Popovic ◽  
Dusan Sladic ◽  
Lidija Pfendt
Keyword(s):  
Ionic Strength ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Equilibrium Constants ◽  
Heterogeneous Systems ◽  
Water Systems ◽  
Acidity Constant ◽  
Acid Base ◽  
Protolytic Equilibria

The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25?C at a constant ionic strength of M(NaCl). The acidity constant Ka1 was determined by potentiometric (pKa1 3.20) and spectrophotometric (pKa1 3.26) methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 -1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.

Sign in / Sign up

Export Citation Format

Share Document