Inclusion compounds, with alcohols

The formation of crystal inclusion of 47 and 48 with cyclic ketones of suitable ring size (cyclopentanone, cyclohexanone) and with cyclohexene oxide are also important facts. Corresponding inclusion compounds with alcohols or amines could not be obtained. With reference to the heterocyclic guest molecules, the suitability of the ring size is likely to be the decisive factor for guest inclusion. 

Since a terminal functional group does not appreciably alter the space requirement, urea forms inclusion-compounds with alcohols, aldehydes, carboxylic acids and amines derived from n-C7 and higher hydrocabons. For molecules with cross section too small, the introduction of functional groups of adequate size leads to inclusion. 

Amylose. A component (20-30%) of starch surrounded by amylopectin. A. is a linear a-l,4-glucan, Mr 50000-200000 (see figure at starch). Crystalline A. occurs in various polymorphic forms (A, B, C, and V-A.), that differ in conformation and crystal packing. A. is soluble in water and gives the characteristic blue color with iodine-potassium iodide solution (Lugol s solution) (formation of inclusion compounds, traces of iodide ions are necessary for occurrence of the blue color, formation of I5 ions I -1 I I -1). Because of its predominately unbranched structure, A. can be degraded to oligosaccharides both by a- and by /S-amylase. The screw-like (helical) conformation also allows the formation of inclusion compounds with alcohols. 

Urea forms an isomorphous series of crystalline non-stoichiometric inclusion compounds with n-alkanes and their derivatives (including alcohols, esters, ethers, aldehydes, ketones, carboxylic acids, amines, nitriles, thioalcohols, and thioethers), provided that their main chain contains six or more carbon atoms. 

Some pyrazolones can also form inclusion compounds. Compound (7.14) (in which Ar is meta- or para-pheny-lene) forms inclusion compounds with methanol, ethanol, isopropyl alcohol, acetone, 2-butanone, tetrahydrofuran, and 1,4-dioxane, often with two guest molecules for one host molecule.72... 

We found that some kinds of alcohols form channel-type inclusion compounds with alkaloids such as brucine (72) and sparteine (75), and that the alcohols are easily resolved utilizing inclusion formation. We also found that sparteine can be resolved by inclusion formation with an optically active tertiary acetylenic alcohol. 

These cyclohexa-(-hepta-, -octa-)amyloses are arranged in the crystal lattice of C. in such a way that open, intramolecular channels are formed in which guest molecules can be enclosed in varying amounts up to saturation ("molecular encapsulation ), e.g., gases, alcohols, or hydrocarbons. a-C. also forms a blue-colored inclusion compound with iodine in which the iodine atoms are arranged like a string-of-pearls in the channels. On account of this property C. are used in the production of food, cosmetics, pharmaceuticals, and pesticides as well as for solid phase extractions and for use as high performance separation phases for enantiomeric and diastereomeric mixtures. 

For example, the same dimer complex which contains two molar equivalents of ethanol, underwent photoreaction to give a higher molecular weight polymer (M = 12 000). The formation of such inclusion complexes with the solvent is rather generally observed with similar types of dimers formed with alcohols and some other solvents and, consequently, this enhances photopolymerizability. Such complex formation with a solvent may be one of the promising techniques that can be used for diolehn compounds in order to obtain polymers with high molecular weights. 

A more deviating stoichiometry is found in the case of the inclusion compound of / with /-propanol 77 >. Here the assistance of two independent host molecules is required and results in a 2 1 stoichiometry. Nevertheless, even this unusual host guest ratio gives rise to a similar H-bond pattern (Fig. 18a and type lib in Fig. 19) as found for the inclusions of 1 with simpler alcohols (cf. Fig. 17a), namely the 12-membered ring system. Now, another interesting fact arises, signalling the flexibility of host 1 in its inclusion behavior. This is the formation of host dimers through H-bonds to ensure clathration. 

The linear arrangement of iodine atoms in the amylose inclusion compound has generated much interest right from the early days with respect to its spectroscopic and optical properties 138 -140). It has also been known for many years that polyvinyl alcohol (PVA) behaves similarly, and this was applied by Polaroid Corporation for the manufacture of polarising plastic using stretched sheets of iodine-stained polyvinyl alcohol170). 

Another type of inclusion compd is the layer or sandwich compound. This includes certain hydrated clays (such as halloysite and montmoril-lonite) which form layer-or sandwich-inclusion compds with polar organic molecules (such as alcohols, glycols, some hydrocarbons, etc) which replace the water, loosely bound in clays (Ref 10, pp445-7)... 

---