Proton acidity internationally adopted

The above solvents theory (A) and proton theory (B) have shown that in theory the neutrality point (of the pure solvent) lies for the amphiprotic solvents at pH = pKs and for the aprotic protophilic solvents at a pH somewhere between the highest acidity (of the protonated solvent) and an infinitely high pH. However, the true pH of the neutrality point of the solvent can only be obtained from a reliable pH measurement and the problem is whether and how this can be achieved. For water as a solvent, the true pH = - logaH+ = colog aH+ is fixed by the internationally adopted convention E°m ( H2(latm) = 0... 

Just as the primary structure of heparin and heparan sulfate has a wealth of fine detail, depending on its exact provenance and function, so the exact conformation of a stretch of polysaccharide depends on its exact location in the chain. The key to this conformational flexibility lies in iduronic acid residues, which can adopt either the C4 or the conformation (the glucosamine-derived residues are firmly in the C conformation, as are glucuronic acid residues). Interpretation of vicinal proton proton coupling constants of IdoA residues in terms of an equilibrium between just and conformations suggests the equilibrium changes from 60 40 for internal IdoA residues to 40 60 for terminal residues (Figure 4.84(a)). " ... 

Depending on the reaction conditions and the nature of the ester side chain in the cinnamates, the resorc[4]arenes can adopt different conformational states, namely, 1,2-altemate, 1,3-altemate, or flattened-cone). In particular, when ( )-2,4-dimethoxycinnamic acid methyl ester 1 was reacted with BF3 Et20 at room temperature, only the 1,2-altemate 2a and flattened-cone 2b stereoisomers were obtained in a 2 3 ratio and 75 % overall yield. In the 1,2-altemate conformation, the assignment of the 12- and 16-OMe signals, by INEPT experiments in conjunction with DIF NOE measurements, allowed to establish the correct stereochemistry at C(14). On the other hand, the presence in the H- and C-NMR spectra of only one signal for both external (H-5) and internal (H-28) aromatic protons and the related carbons, as well as a similar pattern for the methoxy group and the aliphatic... 

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