Concerted Mechanisms of the Reactions of Methyl Aryl Carbonates with Substituted Phenoxide Ions
作者:Enrique A. Castro、Paulina Pavez、José G. Santos
DOI:10.1021/jo010022j
日期:2001.5.1
respectively) with substituted phenoxideions are subjected to a kinetic study in water at 25.0 degrees C, ionic strength 0.2 M (KCl). Production of the leaving groups (the nitro derivatives) is followed spectrophotometrically. Under excess of the phenoxideions pseudo-first-order rate coefficients (k(obsd)) are found throughout. Plots of k(obsd) vs substituted phenoxide concentration at constant pH
New supramolecular hosts: Synthesis and cation binding studies of novel Tröger's base-crown ether composites
作者:Alla Manjula、Madhavarao Nagarajan
DOI:10.1016/s0040-4020(97)00759-x
日期:1997.8
A simple and straightforward synthesis of a novel class of supramolecular hosts containing the Tröger's base moiety is reported. The cationbinding properties of these macrocycles were investigated using Cram's picrate extraction method.
The host–guest complexation behavior of cyclic oligosaccharides, permethylated cycloinulohexaose 1, permethylated cycloinuloheptaose 2, and permethylated cycloinulooctaose 3 with metal cations has been characterized by means of UV-visible, NMR, and electrospray ionization (ESI) mass spectrometry. In the crystal state, the structures of 1·K+, 1·Rb+, and 1·Cs+ were same as that of the 1·Ba2+ complex which has a u-u-d-u-u-d (u = up, d = down) furanose ring arrangement for the plane of the crown ring moiety. The association
constants (KS) in THF and in [2H6]acetone at 298 K were evaluated. The binding ability of host 1 with metal cations was of the same degree as that of calix[6]arene derivative 4 and much higher than those of hosts 2 and 3. The thermodynamic parameters of the complexation of host 1 with metal cation in THF were determined, and it was suggested that the entropy change for the solvation of the metal cations was one of the important factors in the complexation equilibrium. It was clarified that the structure of the host 1·K+ complex in solution at low temperature (furanose ring arrangement: u-d-u-d-u-d) was different from that in the crystal state (u-u-d-u-u-d arrangement)
by the coalescence behavior in 1H-NMR. The relative peak intensity of the complex ions of host 1 or 2 with two alkali metal ions in ESI mass spectrometry (in acetone) showed a correlation in the first order approximation with the ratio of the corresponding complex ion concentrations estimated from the KS values.
Cation Molecular Exchanger Based on a Conformational Hinge
作者:Anil Ravi、P. Sivarama Krishnarao、Tatiana A. Shumilova、Victor N. Khrustalev、Tobias Rüffer、Heinrich Lang、Evgeny A. Kataev
DOI:10.1021/acs.orglett.8b02687
日期:2018.10.5
A cation molecular exchanger has been developed that consists of the bipyridine and crown ether receptor subunits. It has been shown that binding of the zinc(II) cation to the bipyridine subunit induces the conformational switching of the crown ether subunits, which results in a release of the potassium cation. Two conformational states of the cation exchanger have been supported by the results from