Between three protons

The assignment of the 3-position and 5-position protons of the glucose residues as well as the 3-position protons of the arabinose units were confirmed by intraresidue NOE S between three protons with the respective anomeric protons due to 1,3-diaxail depolar interactions observed in the NOESY experiment ( vide infra. 

The proton chemical shifts of the protons directly attached to the basic three carbon skeleton are found between 5.0 and 6.8 ppm. The J(H,H) between these protons is about -5 Hz. The shift region is similar to the region for similarly substituted alkenes, although the spread in shifts is smaller and the allene proton resonances are slightly upfield from the alkene resonances. We could not establish a reliable additivity rule for the allene proton shifts as we could for the shifts (vide infra) and therefore we found the proton shifts much less valuable for the structural analysis of the allene moiety than the NMR data on the basic three-carbon system. 

Reaction of [Ir( -Cp )Cl2(/A-Cl)2]2 and pyrazole in the presence of potassium hydroxide leads to complex 105 characterized by the dynamic hydrogen bond between three pyrazole nuclei (86AGE1114). 3,5-Dimethylpyrazole in identical conditicHis produces 106 where two pyrazole nuclei share a proton and one is unprotonated. Addition of tetrafluoroboric acid to 106 yields 107, where the second proton is bonded to the nonchelated ligand. Addition of the third proton causes formation of [Ir( -Cp )(Hpz )3](BF4)2. 

In a solution containing such particles, the conditions for equilibrium in all possible proton transfers must be satisfied simultaneously, In terms of these proton energy levels, we may say that this is made possible by the additivity of the J values. In Fig. 38 the values of J for the three proton transfers have been labeled J1, J2, and J3. From the relation J3 = Ji + Ji) we may obtain at once a relation between the values of Kx, and hence between the equilibrium constants K. In the proton transfer labeled Jt the number of solute particles remains unchanged, whereas in J4 and Jt the number of solute particles is increased by unity. 

Figure 5.14 Pulse sequence for selective indirecty-spectroscopy. The three proton pulses at the center of the evolution period flip attached protons selectively, resulting in decoupling between distant and attached protons. (Reprinted from J. Magn. Reson. 60, V. Rutar, et ai, 333, copyright (1984), with permission from Academic Press, Inc.)...

The interaction energy U( ) between the proton and the empty (di-ionized) acid comprises three parts ... 

While it is beyond the scope of this review to elucidate details of the current views of proton transport across hydrogen bonds in aqueous systems, the reader is referred to the paper by Eikerling et al 148 j hese authors describe the three main options as follows (1) An excess proton can be a part of an H3O+ ion in which all of the three protons are equivalent. (2) The proton is placed between the two water molecules in the hydrogen bond in an HsOz" " grouping, in the view of Zundel. (3) The proton is a part of an Eigen H9O4+ cluster comprised of an H3O+ ion and three H2O molecules strongly attached to each of the three protons of the HaO" " species. ... 

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