Benzene ring, structure

A number of aromatic amines also function as cross-linking agents. By incorporating the rigid benzene ring structure into the cross-linked network, products are obtained with significantly higher heat distortion temperatures than are obtainable with the aliphatic amines. 

In phenol, aniline, and other compounds in which an atom with unshared electron pairs is attached directly to the benzene ring, structures such as = 0 H or especially... 

The electronic structure of the nitrone group, except for the main A structure, includes four canonical B-E structures. In the case of aromatic derivatives, it is necessary to consider the conjugation with the benzene ring (structures F and G)... 

Two basic issues can be distinguished here (i) the physico-chemical nature of zigzag and armchair sites at the edges of fused-benzene-ring structures, including their differences and similarities with respect to polycyclic aromatic hydrocarbon (PAH) molecules, and (ii) the reconstruction of these edges to potentially more stable structures. 

The feasibility of benzenic ring amines, benzenic ring structures and aliphatic acids oxidation by means of Fenton chemistiy was tested in synthetic, acidic wastewaters by Fenton s reagent electrogenerated at a reticulated vitreous carbon cathode using the flow-cell. The organic molecules considered were phenol (Ph), cresol (Cr), aniline (An) hydroquinone (HQ), catechol (Cat), parabenzoquinone (pBQ) and oxalic acid (OxAc). Their initial... 

According to the experimental evidences shown in Tables 1 and 2 and Figures 10 and 13 it can be concluded that Fenton chemistiy can oxidize azo dyes, benzenic ring structures and aliphatic acids, provided that the catalyst remains in the active form. 

The pyrylium cation is isoelectronic with pyridine it has the same number of electrons and, therefore, we also have aromaticity. Oxygen is normally divalent and carries two lone pairs. If we insert oxygen into the benzene ring structure, then it follows that, by having one electron in a p orbital contributing to the aromatic sextet, there is a lone pair in an sp orbital,... 

When there are two or more substituents on a benzene ring, structural isomerization can result. For instance, there are three possible isomers of xylene (dimethylbenzene). The isomers are commonly designated as ortho, meta, and para. A letter (o, m, or p) designates the isomeric position. 

Fig. 2. Representative hallucinogenic drugs which hear structural similarities to some of the monoamine transmitters. It has been hypothesized that these similarities may cause the hallucinogens 10 mimic natural transmitters at synaptic receptors in the brain. Note presence of benzene-ring structure in these substances, a structure that is present in four out of the live monoamines previously shown. Also note presence of indole ring in psilocybin and lyseigic acid diethylamide, a structure that is also present in the monoamines serotonin and histamine...

Toluene and xylene have benzene ring structures with one and two methyl branches, respectively. 

Aromatic hydrocarbons contain the benzene ring structure. So hydrocarbons may be classified as follows ... 

The reactivity of benzene towards substituting reagents is linked with the fact that in the course of substitution, not only is resonance of the benzene ring structure preserved, but the possibility of resonance structures involving the substituting groups may occur. This problem will be discussed later. 

In addition to aromatics with benzene ring structures, modern refinery processes tend to increase the number of hydrocarbons with simpler types of carbon ring structures. Typical chemicals include cyclopentane, where the straight-chain pentane has been wrapped into a five-carbon ring. Other transformations of aliphatic hydrocarbons include cylcohexane and cyclopentane. These ring compounds are usually called naphthenes. 

It would appear that most of the benzene ring structures in humic substances have two or more substituents, such as carbonyl, carboxyl, hydrocarbon, hydroxyl, and methoxyl and other ether functional groups. The evidence from identification of the products of degradation reactions, and more recently from NMR data, suggests that aliphatic hydrocarbons and aliphatic and aromatic ether groups link the core components in the macromolecules, and that carbonyl, carboxyl, and hydroxyl substituents are likely to be attached to some of the aliphatic hydrocarbons (Hayes and Swift, 1978). 

Aromatic hydrocarbons are of special commercial importance. The benzene ring structure, with six carbons and three double bonds, is the fundamental aromatic unit. This molecule can have one or more hydrogen substitutions with side chains, resulting in alkyl benzenes (e.g. the TEX in BTEX [benzene, toluene, ethylbenzene and xylene]) or two or more aromatic rings may be fused together to form polycyclic aromatic hydrocarbons (PAHs). 

Ibach and Rowe found the reconstructed surface structures to be very stable to hydrogen adsorption, in that on 111 7x7 and 100 2 x 1 surfaces, no change in LEED patterns occurred up to saturation coverage. The favoured interpretation was based on the model of clean surface reconstruction proposed by Lander [76] and extended by Phillips [202], whereby surface vacancies produce warped benzene ring structures in the first and second surface layers, and such distortions are too large to be removed by hydrogen adsorption. The 111 2 x 1 structure was found to be somewhat less stable, however, and the fractional order spots disappeared on hydrogen adsorption. This was related to the Haneman clean... 

A number of aromatic amines also function as epoxy hardeners. Since they introduce the rigid benzene ring structure into the cross-linked network, the resulting products have significantly higher heat-distortion temperatures than are obtainable with the aliphatic amines (see Table 4.27). For example, metaphenylenediamine (MPDA) (shown below) gives cure resins with a heat distortion temperature of 150°C and very good chemical resistance. The hardener finds use in the manufacture of chemical resistance laminates. 

Amite A trade name for Akzo Chemical s high intrinsic viscosity PET that can be extrusion blow molded, aromatic An unsaturated hydrocarbon with one or more benzene ring structures in the molecule. The name refers to the strong and unpleasant odor of most substances of this nature. See chemical benzene ring radiation-induced reaction. 

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