Social Isomers

The limitations on the translational motions of molecules inside capsules are easily appreciated as the structure of the capsule itself provides mechanical boundaries. But there are also restricted motions of tumbling and, as we encountered above, spinning. 

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The isomer with isopropyl groups in the narrower center of the assembly appears energetically inaccessible. But with p-ethyl-toluene the most favored isomer places the ethyl groups in the center and, unaccountably, the unsymmetrical isomer represents only a few percent of the mixture as shown in Fig. 12, although it is statistically favored. In contrast, p-methylstyrene is well behaved and shows exactly what is expected from a statistical distribution of social isomers. Simple... 

Fig. 12 Cartoon representation of the social isomers of (a) p-cymene, (b) p-ethyl-toluene, and (c)...

Fig. 32.8 (a) Social isomers (A and B) generated from the self-assembly of dimeric capsule 12 12 in CHCI3 (blue) in the presence of p-ethyltoluene. Both extremes of p-ethyltoluene (ethyl and methyl groups) are highlighted in different colors (pink and green, respectively), (b) Possible arrangements for co-encapsulated CHCI3 (blue) and isopropyl chloride 18 (pink) within capsule 12 12. Complexes II and III (and IV and V) are isomeric constellations... 

Formation of the same social isomers by a-, P-, and y-picolines and toluene as co-guests by... 

Two model methane— benzene and methane— tetrachloromethane systems have been tested in [99] to determine the effect of isotopic substitution on the stabilities of the corresponding weakly bonded social isomers of these co-guests (Scheme 3.98) within the cavity of 429. Attraction between the methyl group and benzene is reported to be relatively large due to strong dispersion... 

Ajami D, Theodorakopoulos G, Petsalakis ID, Rebek J Jr (2013) Social isomers of picohnes in a small space. Chem Eur J 19(50) 17092-17096... 

Fig. 7.11 Single molecule interactions of solvents and solutes. Left The coencapsulation of chloroform and Af-methyl-p-toluidine shows two social isomers, in which the interaction of the chloroform with the iV-methyl group is favored. Right coencapsulated benzene withp-ethyl-toluene. These social isomers do not interconvert within the capsule, as the p-disubstituted aromatics are too long to tumble inside...

For the last few decades, the use of optically pure compounds has significantly increased for economic, environmental, and social reasons. Particularly, pharmaceutical industries desire to produce the active isomer of chiral drugs in optically... 

Mixtures of pheromones can often be complex and demanding to separate, particularly when isomers of molecules are present. This is particularly acute in the study of social insect cuticular hydrocarbons and which are often complex mixtures of 50 or more different hydrocarbons of increasing chain length (Figure 8). For these mixtures the separation of isomeric hydrocarbons such as 9-, 11-, and 13-methyl-heptacosane is not possible, which has a consequent impact on peak integrations and statistical correlation of these data with colony function. 

A case-control study of sudden cardiac death found that higher concentrations of trans isomers of linoleic acid in adipose tissue, compared with lower concentrations, were associated with increased risk of sudden death. After controlling for smoking and making an allowance for social class, this relationship became insignificant. 

V-GAS. A term used by the Russians and others for the variant of VX developed by the Union of Soviet Social Republics (USSR). VX and V-gas (Cyrillic B-ras) are isomers they share the same chemical formula (CjjH2gN02PS) and molecular mass, but their structures differ. Their chemical and physical properties are nearly identical. 

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