Molecular Aromaticity

Clearly, the hardnesses of thermoplastic polymers are not intrinsic. They depend on various extrinsic factors. Only trends can be cited. For example, as the molecular weight in polyethylene materials increases, they become harder. And, as the molecular aromaticity increases, a polymeric material becomes harder. Thus, higher molecular weight anthracene is harder than napthalene and more aromatic Kevlar is harder than polymethacrylate. 

Therefore, most likely high heating rates prevail de-polymerization of hydrolytic lignin accompanied by removal of low molecular fragments. At low heating rates important become the slow processes of poly-condensation and thickening of low molecular aromatic compounds required to form microstructures with the smallest pores. 

The most likely mode for the aggregation of macrocycles 11 involves inter-molecular aromatic stacking. Face-to-face stacking of the macrocycles can be realized by the relative rotation of adjacent macrocycles, which avoids the... 

On the basis of the results obtained one may draw a conclusion that there exists a certain relationship between the concentration of acidic sites of different types of zeolite and Mo content. In this coimection, to produce a catalyst e diibiting a high activity in the process of methane dehydroaromatization, it is necessary to optimise the relationship between the acidic sites number of a zeolite and the number of active sites connected with different Mo forms. The highest methane conversion per one run and maximal yield of aromatic hydrocarbons are reached for the sample containing 4.0 mass% of Mo nanopowder. The development of the mesoporous zeolite structure is an important factor promoting the activity of Mo-ZSM-5 in the reactions of the formation of high-molecular aromatic compounds. 

Whitehead and Tinsley state further that some fractionation of humic acid has been achieved by chromatographic and electrophoretic procedures, but it has not been possible to detect any clear-cut differences between the fractions. The predominantly aromatic or heterocyclic nature of humus, apart from the polysaccharide fraction, is now well established, but the inability to identify distinct components has lead to the view that humus results from the copolymerization of a number of different small units. Evidence of the units involved is sparse, since very few small molecular aromatic compounds have actually been detected in soils. When humus has been degraded by oxidative procedures, a wide variety of phenols, phenolic aldehydes and phenolic acids have been obtained but the identified products account for only 0.5—1.3% of the original humic acid. 

This is a fundamental result of actual exact HUR treatment for chemical bonding. However, further application of the ELFp index (4.568) for explaining—for instance— the molecular aromaticity, see Volume III of this set, in terms of geometry of bonding and the amount of quantum fluctuation present, are in progress and will be in the future communicated. 

The reaction mechanism of low-molecular aromatic nitro compounds as inhibitors or retarders with growing polymer radicals has been extensively studied (1). By summing up these results, the scheme for the reaction of aromatic nitro groups on the trunk polymer with growing polymer radicals is expected to be as given in Figure 3. 

Molecular aromatic clusters " have also been studied. Gallium phos-phonate cages (Fig. 19) containing alkali metal ions, cyclic hydrocoppers,(Fig. 20), quasi-aromaticity in the transition metal clusters... 

The application of quantitative methods for the evaluation of the molecular aromaticity is common (Bird 1992 Schleyer et al. 1996 Fores et al. 1999 Cyranski et al. 2002 Bultinck et al. 2005 Espinosa et al. 2005 Mitchell et al. 2005 Zborowski et al. 2005 Shishkin et al. 2006 Tarko 2008a Tarko 2010) however, the listing of aromaticity descriptors has emerged recently (Tarko 2008a Tarko 2010). 

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