ABSTRACT
This chapter discusses molecular forces to maintain integrity of the structure of compounds, especially proteins. Noncovalent bond energies are difficult to measure quantitatively, but generally are one to three orders of magnitude smaller than covalent bonding energies. Short-range forces are repulsive, having their quantum mechanical origin in the overlap of electron density of adjacent molecules. The hydrophobic effect arises from the unfavorable interactions between water molecules and the nonpolar residues of a protein. Hydrophile lipophile balance (HLB) scale for the emulsification of lipids with emulsifiers is based on a similar concept to that of solvation of solutes in solvents. The strong electric field of cations, along with their tendency to associate with the oxygen atoms of water molecules, results in the normal structure of water being broken in the presence of cations. Anions readily associate with the available hydrogen atoms of normal water assemblies.
