Noncovalent Interactions between Molecules

When thinking about chemical reactivity, chemists usually focus their attention on bonds, the covalent interactions between atoms within molecules. Also important, however, particularly in large biomolecules like proteins and nucleic acids, are a variety of interactions between molecules that strongly affect molecular properties. Collectively called either intermolecular forces, van der Waals forces, or noncovalent interactions, they are of several different types dipole-dipole forces, dispersion forces, and hydrogen bonds. 

Dipole-dipole forces occur between polar molecules as a result of electrostatic interactions among dipoles. The forces can be either attractive or repulsive depending on the orientation of the molecules—attractive when unlike charges 

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Of the two vitamins A and C, one is hydrophilic and water-soluble while the other is hydro-phobic and fat-soluble. Which is which  

FIGURE 2.6 Dipole-dipole forces cause polar molecules (a) to attract one another when they orient with unlike charges together but (b) to repel one another when they orient with like charges together. 

FIGURE 2.7 Attractive dispersion forces in nonpolar molecules are caused by temporary dipoles, as shown in these models of pentane, 

Perhaps the most important noncovalent interaction in biological molecules is tbe hydrogen bond, an attractive interaction between a hydrogen bonded to an electronegative O or N atom and an unshared electron pair on another O or N atom. In essence, a hydrogen bond is a very strong dipole-dipole interaction 

CHAPTER 2 POLAR COVALENT BONDS ACIDS AND BASES 

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Dispersion force (Section 2.13) A noncovalent interaction between molecules that arises because of constantly changing electron distributions within the molecules. 

Wade D (1999) Deuterium isotope effects on noncovalent interactions between molecules. Chem Biol Interact 117 191-217... 

The self-assembling process involves noncovalent or weak interactions (van der Waals, electrostatic, and hydrophobic interactions, hydrogen and coordination bonds, and r-7T stacking). This process corresponds to a variation of reversed pore structures. Most ordered mesoporous materials are derived from the thermodynamically stable and ordered a regates spontaneously driven by the noncovalent interactions between molecules. These aggregates come from the cationic, anionic and nonionic surfactants, neutral amines, block copolymers, or their mixtures (Figure 13.1). They are disordered on the atomic or... 

The concept of supramolecular chemistry was introduced in 1978. Generally, it refers to weak, noncovalent interactions between molecules. However, Dance has recently proposed an extension of the concept of supramolecular... 

This section presents an overview of the nature of weak noncovalent interactions between molecules (and atoms). Readers interested in more detail are directed to classic references such as the 1954 text by Hirschfelder, Curtiss and Bird, the 1971 book by Margenau and Kestener, the 1996 monograph by Stone," as well as some more recent sources. 

A noncovalent interaction between molecules in which a hydrogen that is bound to an electronegative atom interacts with an electron-rich atom on another molecule. See Hydrogen Bonding 1 and Hydrogen Bonding 2. 

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