Cation, name origin

The origin of cyclopropenone chemistry goes back to the successful preparation of stable derivatives of the cyclopropenium cation <5 3), the first member of a series of Huckel-aromatic monocyclic carbo-cations possessing a delocalized system of (4n + 2)-7r-electrons. This experimental confirmation of LCAO-MO theory stimulated efforts to prepare other species formally related to cyclopropenium cation by a simple resonance description of electron distribution, namely cyclopropenone 7 and methylene cyclopropene (triafulvene) 8 ... 

The same way was used by Yoon and Kim (2005) for the preparation of 5-(p-methoxyphenyl)thian threnium ion incorporated in a calyx[4]arene. Namely, the ratio of starting materials, methoxycal-ixarene to the thianthrene cation-radical perchorate, was 1 10. The product of such 5-anisylation of thianthrene was further transformed into a calixarene bearing an additional o-phenylene thio-macrocycle. This macrocylization is beyond the scope of this book the original paper by Yoon and Kim (2005) could be recommended for those who interested in. It is worth noting only one practical importance of the calixarene-phenylene thiomacrocycle here It selectively extracts silver(l-l-) by both calixarene and thiomacrocycle. Each molecule of this combined complexon takes up two silver cations, so that extractability achieves 165%. 

There are three types of ionotropic glutamate receptors NMDA, a-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA), and kainate receptors (Fig. 1). Each is principally activated by the agonist bearing its name and is permeable to cationic flux hence, their activation results in membrane depolarization. Ionotropic glutamate receptors were originally classified based on three selective, synthetic agonists quisqualate, kainate and NMDA. After the discovery of metabotropic receptors, it became clear that quisqualate also interacts with them. Since that time, quisqualate-sensitive ionotropic receptors have been classified by the more selective agonist AMPA. 

It is interesting to apply this definition, which is a clear improvement over Winstein s original definition of homoaromaticity, to a particular case, namely the homotropenylium cation. 

While the selective interactions of functionalised calixarenes with cations have been studied broadly for almost three decades, the application of cal-ixarene-based receptors for anion recognition is a relatively new research topic [2]. This review is focused on recent developments in the design and synthesis of calixarene-based anion receptors. Although the name calixarene was originally designated only for phenol-formaldehyde derivatives 1, recently many structural variations and mutations have been formed. Some of them, such as calixpyrroles [3], are widely used for anion recognition nevertheless, this review is restricted only to classical calixarenes 1 and newly discovered thiacalix-arenes 2 [4]. 

Huisman and van der Schaaf (H30) have applied Moore and Stein s 1954 procedure, but with another resin, namely, a cation exchanger Zeo-carb 225 (Zerolit 225). This modification does not seem to provide better results than the original procedure. 

Figure 21 indicates the anion interstitial currents through the layers. The coordinate system is chosen to be the same as that already utilized for cation interstitial diffusion, namely that illustrated in Fig. 18. Because all anion interstitials originate at the oxygen interface, the anion interstitial currents decrease in magnitude in the order i + 1, i, i — 1,. . . , as noted in Fig. 21. The difference current Jf(ai) — J VI serves to increase the thickness...

Conventional IPC separations were achieved by adding organic amines and ammonium salts of varying chain lengths as cationic IPRs for anionic analytes and alkyl or aryl sulfonates and sulfates as anionic IPRs for cationic solutes. Since these IPRs exhibit good tensioactive properties, IPC was originally named soap chromatography [1]. 

---