Molecular structure aromaticity

Various industrial sectors related to textiles, paper, and photography use dyes of synthetic origin with a complex aromatic molecular structure, which are frequently discharged in industrial effluents. One solution to these environmental problems is to use oxidative enzymes that destroy colored compounds and that may be of practical interest for the decolorization of synthetic dyes. Enzymes such as LiPX and MnPX are involved in the decolorization of synthetic azo dyes, such as Acid Orange II. 

The peripheral selenodiazole rings of porphyrazine (169) can be opened upon treatment with H2S with the proposed formation of the octaaminoporphyrazine (184), which was not isolated and instead converted into the tetrakis(pyrazino)porphyrazine (185) (Scheme 34) (171). Other heterocycles have been fused on the periphery of porphyrazines, such as l,3-dithiol-2-thione in order to extend the aromatic core (172). Macrocyclization of 4,5-dicyano-l,3-dithiole-2-thione (186) under Linstead conditions in the presence of magnesium butoxide produced the symmetrically substituted tetrakis(l,3-dithiol-2-thiono)porphyrazine (187) (Scheme 35). Due to the low solubility of porphyrazine 181, a consequence of the planar aromatic molecular structure, a full characterization of this compound could not be accomplished. 

X-Ray crystallographic examination of 23 displayed a completely planar (and therefore aromatic) molecular structure <2000T63>. 

By acylation of polymers 2 and 2 the benzoate ester polymers and the benzamide polymers were synthesized. Charging studies of these systems revealed relationships betwa both aliphatic and aromatic molecular structures and charging.The charging of the acylated polymers was found to be less positive (more negative) than the parent polymers. Silylation causes similar changes in hydroxy or amino functionalized materials, as does acylation of alcohols such as poly(vinyl alcohol) and ethyl cellulose. ... 

HMO theory is named after its developer, Erich Huckel (1896-1980), who published his theory in 1930 [9] partly in order to explain the unusual stability of benzene and other aromatic compounds. Given that digital computers had not yet been invented and that all Hiickel s calculations had to be done by hand, HMO theory necessarily includes many approximations. The first is that only the jr-molecular orbitals of the molecule are considered. This implies that the entire molecular structure is planar (because then a plane of symmetry separates the r-orbitals, which are antisymmetric with respect to this plane, from all others). It also means that only one atomic orbital must be considered for each atom in the r-system (the p-orbital that is antisymmetric with respect to the plane of the molecule) and none at all for atoms (such as hydrogen) that are not involved in the r-system. Huckel then used the technique known as linear combination of atomic orbitals (LCAO) to build these atomic orbitals up into molecular orbitals. This is illustrated in Figure 7-18 for ethylene. 

As Olah et al. have reported (81JOC2706), iV-nltropyrazole in the presence of Lewis or Brpnsted acid catalysts is an effective nitrating agent for aromatic substrates. The greater lability of the N—NO2 bond in iV-nltropyrazole compared with aliphatic nltramines was discussed on the basis of its molecular structure as determined by X-ray crystallography. 

Pyrano[4,3-6]pyran-2,5-dione, 7-methyl-aromaticity, 3, 639 Pyranopyrandiones aromaticity, 3, 639 dipole moments, 3, 627 synthesis, 3, 795 tautomerism, 3, 644 Pyranopyranones molecular structure, 3, 624 Pyranopyrans synthesis, 3, 760, 784 Pyranopyrazoles synthesis, 5, 321, 330 Pyranopyrazolones synthesis, 5, 334 Pyranopyridine synthesis, 3, 834 Pyranoses... 

On the basis of data obtained the possibility of substrates distribution and their D-values prediction using the regressions which consider the hydrophobicity and stmcture of amines was investigated. The hydrophobicity of amines was estimated by the distribution coefficient value in the water-octanole system (Ig P). The molecular structure of aromatic amines was characterized by the first-order molecular connectivity indexes ( x)- H was shown the independent and cooperative influence of the Ig P and parameters of amines on their distribution. Evidently, this fact demonstrates the host-guest phenomenon which is inherent to the organized media. The obtained in the research data were used for optimization of the conditions of micellar-extraction preconcentrating of metal ions with amines into the NS-rich phase with the following determination by atomic-absorption method. 

Aromatic — organic molecular structure having the benzene ring (C H ) as the basic unit (e.g., toluene, xylene). 

Tlie importance of bis(cyclopeniadienyl)irou (Fe(jj -C5H3)2( in the developmenl of organo-metallic chemistry has already been alluded to (p. 924). Tile compound, which forms orange crystals, mpl74°, has extraordinary thermal stability (>500°) and a remarkable structure which was unique when first established. It also has an extensive aromatic-lype reaction chernisiry which is reflected in its common name ferrocene The molecular structure of ferrocene in the ciysialline slac features two parallel cyclopentadienyl rings at one lime Ihese... 

By clicking the appropriate buttons on the form, the user can combine molecular structure queries of sample, CSP and solvent, using operators AND, OR, NOT with data queries in one search. A query for the search of chiral separations of alpha-aromatic acids on any polysaccharide phases coated on silica gel providing an alpha value superior to 1.2 is shown in Eig. 4-4. 

The naphthenes and aromatics both have cyclic (or ring-like) molecular structures and both possess high octane numbers. Napthenes are saturated and aromatics contain alternate double bonds on their ring. They are typically found in gasoline. The naphthenes also are an important part of kerosene. 

Increasing the octane number of a low-octane naphtha fraction is achieved by changing the molecular structure of the low octane number components. Many reactions are responsible for this change, such as the dehydrogenation of naphthenes and the dehydrocyclization of paraffins to aromatics. Catalytic reforming is considered the key process for obtaining benzene, toluene, and xylenes (BTX). These aromatics are important intermediates for the production of many chemicals. 

The heptane insoluble (ASTM D-3279) method is commonly used to measure the asphaltene content of the feed. Asphaltenes are clusters of polynuclear aromatic sheets, but no one has a clear understanding of their molecular structure. They are insoluble in C3 to paraffins. The amount of asphaltenes that precipitate varies from one solvent to another, so it is important that the reported asphaltene values be identified with the appropriate solvent. Both normal heptane and... 

The n-d-M correlation is an ASTM (D-3238) method that uses refractive index (n), density (d), average molecular weight (MW), and sulfur (S) to estimate the percentage of total carbon distribution in the aromatic ring structure (% C ), naphthenic ring structure (Cj,), and paraffin chains (% Cp). Both refractive index and density are either measured or estimated at 20°C (68°F). Appendix 4 shows formulas used to calculate carbon distribution. Note that the n-d-M method calculates, for example, the percent of carbon in the aromatic ring... 

Many drug-like molecules have aromatic substituents and thus have limited aqueous solubility. A routine practice is to dissolve stock drugs in a solvent known to dissolve many types of molecular structures. One such solvent is... 

Poly(p-pheny lene)s, PPPs, constitute the prototype of rigid-rod polymers and are currently being intensively investigated [1]. The key role of PPPs follows from their conceptually simple and appealing molecular structure, from their chemical stability, and from their superior physical properties [2], In turn, this is the result of important advances made in aromatic chemistry over the last few years. The following section gives an overview of the most common methods to generate poly(p-phenylene)s via different synthetic approaches. 

The photoinduced absorption and the electrical characteristics of the conjugated LPPP show that the optoelectrical properties are strongly dependent on charge carrier traps in the bandgap. From aromatic molecular crystals it is known that impurities and structural imperfections form localized states [34]. LPPP forms homogeneous and dense films with a mean interchain distance of about 20 A and ncgligi-... 

PET, PTT, and PBT have similar molecular structure and general properties and find similar applications as engineering thermoplastic polymers in fibers, films, and solid-state molding resins. PEN is significantly superior in terms of thermal and mechanical resistance and barrier properties. The thermal properties of aromatic-aliphatic polyesters are summarized in Table 2.6 and are discussed above (Section 2.2.1.1). 

As in molecular chemistry, an alternative path to compensate for electron deficiency is the formation of multiple bonds, through 7r-interactions, as in unsaturated and aromatic molecular systems. Our work in Houston focuses on probing the efficacy of the ZintI concept in rationaUzing stoichiometries, crystal structures and chemical bonding of complex electron-poof ZintI phases that exhibit novel i-systems. Their chemical bonding is reflected by their unusual crystal structures related to unsaturated hydrocarbons [53]. 

Sweetness is a quality that defies definition, but whose complexity can be appreciated merely by examining the molecular structures of those compounds that elicit the sensation. They come in all molecular shapes and sizes, and they belong to such seemingly unrelated classes of compounds as aliphatic and aromatic organic compounds, amino acids, peptides and proteins, carbohydrates, complex glycosides, and even certain inorganic salts. 

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