Hydrogen, molecular, interaction with

Absorption, metaboHsm, and biological activities of organic compounds are influenced by molecular interactions with asymmetric biomolecules. These interactions, which involve hydrophobic, electrostatic, inductive, dipole—dipole, hydrogen bonding, van der Waals forces, steric hindrance, and inclusion complex formation give rise to enantioselective differentiation (1,2). Within a series of similar stmctures, substantial differences in biological effects, molecular mechanism of action, distribution, or metaboHc events may be observed. Eor example, (R)-carvone [6485-40-1] (1) has the odor of spearrnint whereas (5)-carvone [2244-16-8] (2) has the odor of caraway (3,4). 

Finally, a fourth motivation for exploring gas solubilities in ILs is that they can act as probes of the molecular interactions with the ILs. Information can be discerned on the importance of specific chemical interactions such as hydrogen bonding, as well as dipole-dipole, dipole-induced dipole, and dispersion forces. Of course, this information can be determined from the solubility of a series of carefully chosen liquids, as well. FLowever, gases tend to be of the smallest size, and therefore the simplest molecules with which to probe molecular interactions. 

Glendening, E. D., Streitwieser, A., 1994, Natural Energy Decomposition Analysis An Energy Partitioning Procedure for Molecular Interactions With Apphcation to Weak Hydrogen Bonding, Strong Ionic, and Moderate Donor-Acceptor Interactions , J. Chem. Phys., 100, 2900. 

The second type of solvent-related effect which commonly occurs is observed when a mixture of 1-octanol and 1,8-octanediol is analyzed in two different eluents. In chloroform, the two alcohols are not resolved due to their similar molecular size. In THF, however, resolution nearly to baseline can be achieved due to differentiation of the alcohols on the basis of hydrogen bonding interactions with THF. Octanediol, having two sites for interaction, forms a species with a significantly larger effective size in solution than does octanol which has only one site for interaction. The separation is therefore enhanced. 

Figure 12.1 shows the molecular interaction fields produced by the hydrogen probe interacting with the amino acid sidechains inside the active site cavities of the cytochromes. Such MIFs are important in evaluating the available volume in the active site cavities, and the shape of these cavities. 

Figure 23. A molecular-level extension. Thread 31H " can undergo a hydrogen-bonding interaction with macrocycle 32 + and an acceptor-donor interaction with macrocycle 2 (MeCN, 298 K). Once the two connections have been established, photoinduced electron transfer occurs from the excited state of the Ru(bpy)3 + moiety of macrocycle 32 to the bipyridinium unit hosted in...

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