The condensation reaction between p-tert-butylphenol and formaldehyde leads in a single step to good yields of cyclic oligomers in which, depending on the reaction conditions, either four, six, or eight phenol units are joined by methylene bridges. The beakerlike shape of the most stable conformation of the tetramer has led to their being given the name “calixarenes” (calix = chalice). Resorcinol can undergo condensation in a similar manner with a variety of aldehydes to afford cyclic tetramers with the same basic structure (the resorcarenes). In both cases the reaction does not require the use of dilution techniques, so that large quantities of product can be readily obtained. In addition, the parent compounds can be modified in various ways, in particular at the phenolic hydroxy groups or the phenyl residues; these approaches can be used separately or in combination. Calixarenes are thus ideal starting materials for the synthesis of various types of host molecules and can also act as building blocks for the construction of larger molecular systems with defined structures and functions. Their potential applications range from use as highly specific ligands for analytical chemistry, sensor techniques and medical diagnostics to their use in the decontamination of waste water and the construction of artificial enzymes and the synthesis of new materials for non-linear optics or for ultrathin layers and sieve membranes with molecular pores.

Calixarenes, Macrocycles with (Almost) Unlimited Possibilities

We discuss the origins and the fundamentals of Green Analytical Chemistry (GAC), based on the literature published about clean, environmentally-friendly or GAC methods. We pay special attention to the strategies and the tools available to make sample-pretreatment and analytical methods greener. We consider that the main principles are to replace toxic reagents, to miniaturize and to automate methods, making it possible to reduce dramatically the amounts of reagents consumed and wastes generated, so reducing or avoiding side effects of analytical methods. We also consider on-line decontamination or passivation of wastes to be of special interest in making analytical chemistry sustainable.

/pdf/green-analytical-chemistry-2j89cop1pd.pdf

Green Analytical Chemistry

Solid phase extraction of trace elements

o-Quinone methides: intermediates underdeveloped and underutilized in organic synthesis

http://www.jsps.org/alumni/documents/JohnFossey20101129.pdf

Boronic acid building blocks: tools for self assembly.

Ion-exchanger phase absorptiometry for trace analysis.

N-Methylglucamine resin has been shown to be a good adsorbent for borate or boric acid. Above ca. pH 6, the boron adsorbability of this resin increased with a maximum around pH 9. The maximum distribution ratio was higher than 106, however, further increase in pH resulted in a decrease in the distribution ratio. The combination of distribution and 11B MAS NMR measurements revealed the formation of a 1:1 tetradentate complex of B(OH)4- with the N-methylglucamine group. The calculated pH-dependence of boron adsorption agreed well with the experimental results with respect to the -log [H+] values in the resin phase (not in the external solution) estimated by 31P NMR measurements. The maximum adsorption around pH 9 of the equilibrated solution is due to the fact that the pH in the resin phase remains higher than that in the external solution. Therefore, B(OH)3/B(OH)4- is selectively concentrated into the resin phase and by the dehydration condensation B(OH)4- forms the 1:1 tetradentate complex with the anchor group. The overall formation constant of the complex was estimated to be 104.0±0.1, which was almost the same magnitude as that of the 1:1 monochelate complex with an α,β-diol site of N-methyl-D-glucamine (which is an analogue of the functional group of the resin) in aqueous solutions of pH 5.1–7.4. However, the binding structures of each 1:1 complex with the N-methyl-D-glucamine group are quite different in the aqueous solution and in the crosslinked polymer.

Complexation of boric acid with the N-methyl-D-glucamine group in solution and in crosslinked polymer

Deep source CO2 in natural waters and its role in extensive tufa deposition in the Huanglong Ravines, Sichuan, China

Geochemical and stable isotope studies on natural water in the Taroko Gorge karst area, Taiwan—chemical weathering of carbonate rocks by deep source CO2 and sulfuric acid

Implementation of ion-exchanged absorptiometric detection in flow analysis systems

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