Hydrogen atom bonding interactions

In some force fields the interaction sites are not all situated on the atomic nuclei. For example, in the MM2, MM3 and MM4 programs, the van der Waals centres of hydrogen atoms bonded to carbon are placed not at the nuclei but are approximately 10% along the bond towards the attached atom. The rationale for this is that the electron distribution about small atoms such as oxygen, fluorine and particularly hydrogen is distinctly non-spherical. The single electron from the hydrogen is involved in the bond to the adjacent atom and there are no other electrons that can contribute to the van der Waals interactions. Some force fields also require lone pairs to be defined on particular atoms these have their own van der Waals and electrostatic parameters. 

The complex OsHCl(CO)(P Pr3)2 reacts with HX (X = H, SiEt3, Cl) molecules to give derivatives of the type OsXCl(r)2-H2)(CO)(P Pr3)2 (X = H, SiEt3, Cl), where the hydrogen atoms bonded to the osmium atom undergo nonclassical interaction (Scheme 16). 

Turning our attention to the cis isomer, the Css conformation involves a potential sigma nonbonded interaction between the hybrid in-plane oxygen lone pairs, the Cse involves a hydrogen bond, and the Cee conformation involves a sigma nonbonded interaction between the hydroxyl hydrogen atoms. These interactions are pictorialized below ... 

In the present snidy this term is senseless since 5 (G = I) has no hydrogen atoms to interact with the solvents which have hydrogen-bond donor abilities. 

A hydrogen bond is an attractive interaction between a hydrogen atom bonded to a very electronegative atom (O, N, or F) and an unshared electron pair on another electronegative atom. For example, hydrogen bonds occur in both water and ammonia ... 

This chapter considers a number of other types of interactions that are somewhere near the boundaries of a true H-bond. We discuss the details of these interactions and the magnitudes of some of the indicators. One issue discussed is the proton-accepting ability of an electronegative atom when involved in a bond to another electronegative atom, leaving the bond of low or zero polarity. Hydrogen atoms bonded to carbon are typically of low acidity, so their ability to participate in H-bonds is questionable as well. 

Hydrogen bonding (Section 3.3A) An attractive intermolecular interaction that occurs when a hydrogen atom bonded to an O, N, or F is electrostatically attracted to a lone pair of electrons on an O, N, or F atom in another molecule. 

The hydrogen atom can interact between two electronegative atoms, either within one or between two molecules. Hydrogen bonding can be considered as an important interaction (4-40 kJ/mol) between analyte molecules and both the mobile and the stationary phase in LC. In reversed-phase LC, both water and methanol can act both as acceptor and donor in hydrogen bonding, while acetonitrile can only accept, not donate. 

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