Aliphatic guests

Key words. Cyclophane, aromatic guest, aliphatic guest, aqueous solution. 

The range of inclusion adducts formed by the organophosphazenes is very broad, the guest species varying from aliphatic and aromatic hydrocarbons to ethers, ketones and alcohols42. Some of the hosts [e.g., tris(o-phenylenedioxy)cyclotriphosphazene 12)] form clathrates not only when recrystallized from organic solvents but also... 

This host network, termed the helical tubuland structure type 7,8), is unique. The walls of the canals are lined only by aliphatic hydrocarbon, and the hydrogen bonded spines are insulated from the guest canals. Powder diffraction and IR measurements indicate that when 1 is crystallised from acetonitrile the same host crystal structure occurs, but devoid of guest. This has the unusually low calculated density, 1.02 g cm 3. 

Unlike the crystalline cycloamylose complexes, combining ratios of host to guest in solution are usually 1 1. A notable exception is the interaction of the cycloamyloses with long chain aliphatic carboxylic acids. Solubility plots suggest that as many as four cycloheptaamylose molecules may interact with a single molecule of dodecanoic acid (Schlenk and Sand, 1961). In analogy to the crystalline state, cycloamyloses may form channels in solution in order to accomodate extended chains. 

The majority of the studies in this series were performed using aliphatic and aromatic ketones as guests. The steroid sites that undergo functionalization vary with the guest used. Thus, irradiation of the DCA-diethyl ketone complex affords the product, 165, of addition of the ketone to the 6-equatorial position. Exposure of the DCA-cyclohexanone complex to light brings about formation of steroid functionalized in the D-ring, 166, while irradiation of the acetophenone complex affords the 5-fi-DCA adduct, 167. 

Many workers have shown [3,19] that the gallery height in LDHs containing long chain aliphatic carboxylate, dicarboxylate, sulfonate or sulfate guests increases as the chain length increases. For the case of o, 6t)-dicarboxylate anions OOC(CH2)nCOO , the basal spacing shows a mean increase of 0.127 nm/CH2 from n = 3 to 12 as shown in Fig. 21 [213] for Mg/Al LDH... 

In contrast to dendrimers built up from aliphatic chains, polyphenylene dendrimer micelles possess shape and size persistent cavities due to their rigid scaffold which strongly depends on the type of dendrimer. In this case a selective incorporation of guest molecules, e.g., fluorescent dyes, should be possible, dependent on the size of the guest molecule and the cavity of the host. The non-covalent uptake of dyes with an appropriate size thus allows the investigation of their interactions within the dendritic micelle. In our case we made the second-generation polyphenylene dendrimer 48, which bears 16 carboxy-functions at the periphery, by starting from a tetrahedral core and an appropriately... 

Guest D et ah Aliphatic carboxylic acids. In Clayton GD, Clayton EE (eds) Patty s Industrial Hygiene and Toxicology, 3rd ed, rev, Vol 2C, Toxicology, pp 4909 911. New York, Wiley-Interscience, 1982... 

Sheppod, T.J., Petti, M.A. and Dougherty, D.A. (1986) Tight, oriented binding of an aliphatic guest by a new class of water-soluble molecules with hydrophobic binding sites. J, Am. Chem. Soc., 108, 6085-6087. 

The restricted motion of molecules and of fragments such as free radicals formed by photodissociation results in interesting differences in the photochemistry of some molecules in solution or as guests in inclusion compounds. To take one example, the aliphatic ketone 5-nonanone can yield fragmentation or cyclization products via the biradical formed through intramolecular hydrogen atom abstraction (Figure 8.18). In the photolysis of the inclusion compound the cyclization is the preferred reaction, and there is a marked selectivity in favour of the ay-isomer of the cyclobutanol. 

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