7 amylopectin (the two components of starch) to form the cyclodextrins is fascilitated by the natural tendency for chains of alpha 1-4 glucose units to assume a helical configuration. Because of their cyclic structure and the relatively large open space within each molecule (6A for alpha, 8A for beta, and 10-11A for gamma), they readily form monomolecular clathrate compounds. The cyclodextrins show different degrees of inclusion formation with different sized molecules because of their different internal ring sizes. For example (7), alpha has been shown to form adducts with chlorine, bromine, iodine, hydrocarbons, and benzene derivatives with small substituents. Beta interacts with bromine, iodine and almost any organic molecule. Gamma interacts with iodine and only large organic molecules. There has been some controversy as to the exact electronic density of the center of the cyclodextrin void. Broser and Lautsch (5) showed that the stability of the inclusion complex in solution increases with basicity of the enclosed molecule. They therefore agreed that the cyclodextrin represents the electrophillic component of the inclusion complex. Cramer (8) differs with this conclusion. He claims that the hollow space of an occlusion compound is a space of high electron density and behaves in many respects like an electron donor. The hollow spaces of such compounds can be considered as Bronsted and Lewis bases. He states (9) that the Schardinger dextrins form stable inclusion compounds with organic molecules because organic compounds are included in the voids of the cyclodextrin rings where the action upon the electron systems is par- ticularly strong. Because of a state of high electron density in the void, the field energies there are apparently so great that effects appear which are comparable to those in an alkaline medium. In speaking of the combination of two or more atoms or molecules to form a new chemical entity, we may describe the two distinct phenomena of reaction and interaction. Reaction involves the creation of a new compound by the formation of valence bonds. One or more of the classic types of ionic or covalent bonding is involved. Interaction involves formation of a compound where one or more of the bonds involved cannot be described as being of the classic type. These bonds may arise through hydrogen bonding, dipole-dipole interaction, charge transfer, or other attractive forces. The term "complexation" has come to mean this type of chemical interaction. Complexation by means of molecular inclusion formation has received little attention by researchers. Schlenk (34) defines inclusion compounds (or occlusion compounds, as they may be called) as addition compounds in which one compound fits into and is surrounded by the crystal lattice of the other compound. These inclusion compounds can be referred to as "no bond" complexes and are characterized by the lack of adhesive forces between the components of the complex. The enclosing compound may be tube shaped, cage shaped or form open layers. The two compounds are present in constant, but not necessarily stoichiometric proportions. Source: https://www.industrydocuments.ucsf.edu/docs/ffbb0094