Large rings basicity

The most dramatic rate retardations of proton transfers have been observed when the acidic or basic site is contained within a molecular cavity. The first kinetic and equilibrium studies of the protonation of such a basic site were made with large ring bicyclic diamines [72] (Simmons and Park, 1968 Park and Simmons, 1968a). It was also observed (Park and Simmons, 1968b) that chloride ion could be trapped inside the diprotonated amines. The binding of metal ions and small molecules by macrocyclic compounds is now a well-known phenomenon (Pedersen, 1967, 1978 Lehn, 1978). In the first studies of proton encapsulation, equilibrium and kinetic measurements were made with several macrobicyclic diamines [72] using an nmr technique. 

Tetrapyrrole chemical substance consisting of four pyrrole rings, joined together into a single large ring known as a macrocycle, serves at the basic structure of chlorophyll. 

Mogensen, B, T Endo, H Ueda, W Zimmermann and KL Larsen (2000). Analysis of complex formation between large-ring cyclodextrins and aromatic anions. In cydodextrin Prom Basic Research to Market. 10th International Cyclodextrin Symposium, Ann Arbor, Ml, USA CD-ROM edition. 

Section 22.15 The IR and H NMR spectra of phenols are similar to those for alcohols, except that the OH proton is somewhat less shielded in a phenol than in an alcohol. In NMR, an OH group deshields the carbon of an aromatic ring to which it is attached. An OH group causes a shift in the UV-VIS spectrum of benzene to longer wavelengths. The effect is quite large in basic solution because of conversion of OH to 0. ... 

The methyl ethers of large-ring keto[ ]calixarenes 19 (n = 5, 6) have been prepared from the corresponding bromocalixarenes 17 (see below) via a two-step process involving basic hydrolysis, followed by CrOa oxidation of the respective hydroxy methylene derivatives 18 (Eq. 4.12) [22]. 

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