Hydrogen-bonding addity

Abraham, M. H., Zhao, Y. H. Determination of solvation descriptors for ionic spedes hydrogen bond addity and basicity. J. Org. Chem. 2004, 69,... 

Valko, K., Du, C. M., Bevan, C., Reynolds, D. P., Abraham, M. H. Rapid method for the estimation of octanol/water partition coefficient (logP ,) from gradient RP-HPLC retention and a hydrogen bond addity term (EaJ ). Curr. Med. Chem. 2001, 8, 1137-1146. 

The second important influence of the solvent on Lewis acid - Lewis base equilibria concerns the interactions with the Lewis base. Consequently the Lewis addity and, for hard Lewis bases, especially the hydrogen bond donor capacity of tire solvent are important parameters. The electron pair acceptor capacities, quantified by the acceptor number AN, together with the hydrogen bond donor addities. O, of some selected solvents are listed in Table 1.5. Water is among the solvents with the highest AN and, accordingly, interacts strongly witli Lewis bases. This seriously hampers die efficiency of Lewis-acid catalysis in water. 

Cement-forming liquids are strongly hydrogen-bonded and viscous. According to Wilson (1968), they must (1) have sufficient addity to decompose the basic powder and liberate cement-forming cations, (2) contain an acid anion which forms stable complexes with these cations and (3) act as a medium for the reaction and (4) solvate the reaction products. 

This same palladium jt-addity can be employed to activate alkenes towards intramolecular cydization with heteroatom-hydrogen bonds. In contrast to alkynes or allenes, the addition of N H, O—H and other heteroatom-hydrogen bonds across the alkene would formally create a saturated carbon-carbon bond, rather than the unsaturation necessary for aromatic heterocydes. As such, subsequent P-hydride elimination is often required to dired these readions towards aromatic produds, in a Wacker-type alkene oxidation (Scheme 6.28). 

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