Anion Sensing: -/- - download pdf or read online

By Franz P. Schmidtchen (auth.), Ivan Stibor (eds.)

ISBN-10: 3540232478

ISBN-13: 9783540232476

ISBN-10: 354031461X

ISBN-13: 9783540314615

This treatise on anion sensing and popularity represents a brand new addition to a really small variety of books during this area......

Although this Topics volume doesn't hide all of the diversified sessions fo receptors, it does offer new and well timed views to anion chemistry by way of highlighting a number of components which have been as a rule ignored in different reports. the person chapters are well-written and contain references from previous works as much as the current. As such, this quantity could be of curiosity to the neighborhood of researchers attracted to anions in addition to to those that desire to know about the host-guest chemistry of anion popularity and its applications.

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Thorough NMR studies as well as molecular modeling experiments have been applied to explain this efficiency. The structure of the complex of 30 with both enantiomers of N-Ac-Val has been calculated using the Monte Carlo method. Whereas the L-enantiomer is bound to carbamoyl NH in position 12 of the steroid skeleton with its acetyl oxygen, the D-enantiomer is bound to the same place by the oxygen of the carboxylate moiety (see Fig. 2 Å by rotation about the N–Ph bond. The valyl methyls are close to the aromatic rings of the receptor, and are in quite different environments; hence it is not surprising that one is shifted upfield in the NMR spectrum of the complex.

As expected, the aromatic amino acids were preferred (40% extraction efficiency for L-Phe and L-Trp). In the organic phase, no valine was detected. 5%, D-Phe<2%). The same principle follows for the receptor 13, designed and synthesized by Schmidtchen [39]. Both recognition structural units have been changed. The aromatic naphthoyl group has been substituted with the bulkier diphenyl-tertbutylsilyl group and the aza-18-crown-6 unit by a symmetrical triaza analog that is known to recognize the ammonium cation with high selectivity against alkali metal cations.

Schmidtchen the non-monotonous sequence of affinities in the halide series, favouring bromide as the best-fitting guest with respect to size. Although devoid of any catalytically active functionality, the larger host 2 proved functional as a molecular catalyst by virtue of its capacity to stabilize highly delocalized anionic transition states as they occur, for instance in nucleophilic aromatic substitutions. e. a micro-solvent effect) [29]. The efficiency of ammonium hosts can be much enhanced if, supplementary to the charge, hydrogen bonding can be exploited.

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Anion Sensing: -/- by Franz P. Schmidtchen (auth.), Ivan Stibor (eds.)

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