Aromaticity radial

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

These same principles can be extended to systems, such as H3+, with delocalized multicenter er-bonding derived solely from the radial s-orbital combinations. The descriptive term, in-plane aromaticity, [44] includes such cases (see Chapter 3.2.1 for further discussion). 

Fig. 3. 2-4. Radial (bottom) and tangential (top) bonding molecular orbitals for cyclopropane [12e] (left) and hexa-borane(6) dianion (right) illustrating the planar and three dimensional a aromaticity, respectively. Tangential orbitals of [B6H6]2 are triply degenerate.

Discotic disc-like. A similar structure but the radial component is more important. The core is often aromatic and surrounded by 6-8 alkyl chains. 

Initial investigations showed that the treatment of trimethylsilyl nitronate 23a (R1 = Me) with benzaldehyde (R2 = Ph) in the presence of (S,S)-6b (X = HF2, 2 mol %) in TH F at —98 °C for 1 h and at —78 °C for 1 h and subsequent hydrolysis with 1M HC1 at 0 °C, resulted in clean formation of the corresponding nitroalkanol 24 (R1 = Me, R2 = Ph) in 83% yield (anti/syn = 74 26) with 33% ee (anti isomer) (entry 1 in Table 9.5). Notably, the poor diastereo- and enantioselectivities were dramatically improved by switching the catalyst to (S,S)-6c (X = HF2) possessing a radially extended 3,3-aromatic substituent (Ar), and 24 (R1 = Me, R2 = Ph) was obtained in 92% yield (anti/syn = 92 8 with 95% ee (anti isomer) (Table 9.5, entry 2). This asymmetric nitroaldol protocol tolerates various aromatic aldehydes to afford anti-nitroaldols selectively, being complementary to Shibasaki s method... 

In theory, almost any polymer can be used as a reinforcement in an advanced composite. By far the most common polymer fiber, however, is aramid, better known by its trade name, Kevlar. Developed originally for use in belted radial tires, aramid is an aromatic polyamide in which benzene fragments (C6H4) alternate with peptide groups (NHC = Q) in forming a polymeric structure ... 

A classification of solvents can be developed on the basis of the stability of the radial anion produced by reduction of aromatic hydrocarbons, such as naphthalene and anthracene. The solvent reactions of such anions have been widely studied2 and have generally been found to go by a sequence of reactions in either a protic solvent or in the presence of a proton donor in an aprotic solvent 3... 

Figure 11-8. Center of mass radial distribution functions for aromatic groups (benzene and/or phenyl) for two benzene-polystyrene mixtures. The normalization is chosen so that all radial distribution functions approach 1 at infinity. The figure is taken from Miiller-Plathe [78]...

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