Aromatic substance

Aniline.—Burns with a very smoky flame, clouds of soot being produced. Typical of many aromatic substances. i,2 Dibromoethane.—Does not burn until vapour becomes hot and then burns with a slightly smoky flame. Typical of substances rich in halogens such as cldoroform, chloral hydrate, and carbon, tetrachloride. (Note, however, that iodoform evolves copious fumes of iodine when heated in this way.)... 

Nonalcoholic and strong drinks (tea, wine) contain a number of aromatic substances with amino and hydroxyl groups (first of all, there are polyphenolic compounds and alkaloids) which defined sort and quality of drinks. 

Aromaten, pi. aromatic substances, aromatisch, a. aromatic. — aromatisches Mittel, (Pharm.) aromatic.—aromatische Reihe, aromatic series. 

Lignin is a high-molecular, mainly three-dimensional aromatic substance, that, in contrast to polysaccharides, can be hydrolyzed only in small partitions [16] ... 

Aromatic substances, more than any other class of organic compounds, have acquired a large number of nonsystematic names. The use of such names is discouraged, but 1UPAC rules allow for some of the more widely used ones to be retained (Table 15.1). Thus, methylbenzene is known commonly as toluene hydroxybenzene, as phenol ami nobenzene, as aniline and so on. 

Diffusion control can be particularly important in reactions in which two aromatic substances of differing reactivity are reacting with a deficiency of reagent. The more reactive aromatic will react first and since diffusion is slow compared with the rate of reaction it becomes impoverished in the reaction zone, and ensuing reaction will occur mainly with the less reactive aromatic which is now in large excess. The observed relative reaction rate then comes out to be less than it would otherwise be. It follows that this may also be true even when the aromatics are reacting at considerably less than the encounter rate. 

The methods developed in this paper have been applied in a discussion of the structure of aromatic substances, free radicals, etc., to be published soon. 

The only other reaction with an aromatic substance is the C-H insertion into ferrocene [85], giving 41,which illustrates the highly electrophilic character of the phosphinidene complex. Other aromatic C-H insertions have been observed, but these likely occur by means of intermediate P,0- and P,N-ylids,such as the reaction of (0C)5W=PR withbenzophenone and azobenzene that give 42 and 43,respectively [56a, 86]. 

Kennedy DW, SD Aust, JA Bumpus (1990) Comparative biodegradation of aUcyl halide insecticides by the white rot fungus, Phanerochaete chrysosporium (BKM-F-1767). Appl Environ Microbiol 56 2347-2353. Khanna P, B Rajkumar, N Jothikumar (1992) Anoxygenic degradation of aromatic substances by Rhodopseu-domonas palustris. Curr Microbiol 25 63-67. 

The anodic oxidation of organic substances is a complex multistep process. The question as to the depth of oxidation required (and sufficient) lias to be answered in each case. Where intermediate oxidation products pose no ecological risk, one can stop at incomplete oxidation. However, in the anodic oxidation of many aromatic substances, the corresponding quinones are formed in the first step, and these are more harmful than the original substances. Upon more profound oxidation, the benzene rings are broken and aliphatic substances are formed that are almost as harmless as carbon dioxide. 

In the oxidation of aromatic substances at the anode, radical cations or dications are formed as intermediates and subsequently react with the solvent or with anions of the base electrolyte. For example, depending on the conditions, 1,4-dimethoxybenzene is cyanized after the substitution of one methoxy group, methoxylated after addition of two methoxy groups or acetoxylated after substitution of one hydrogen on the aromatic ring, as shown in Fig. 5.55, where the solvent is indicated over the arrow and the base electrolyte and electrode under the arrow for each reaction HAc denotes acetic acid. 

The terms embalming and mummification are often employed as synonyms to refer to the deliberate preservation of corpses so that they keep, as much as possible, their lifelike appearance. To embalm or mummify a dead body is to preserve it by artificial, chemical means. Dehydratation, the removal of water, for example, provides suitable conditions for the preservation of organic mater in general and of corpses in particular many ancient corpses have been mummified by dehydration. In some ancient societies, after the corpse was dry it was impregnated or filled with aromatic substances, usually known as balms, such as molten resin, pitch, or tar, preventing it from becoming unsightly. 

Yoshida has studied anodic oxidations in methanol containing cyanide to elucidate the electrode processes themselves.288 He finds that, under controlled potential ( 1.2 V), 2,5-dimethylfuran gives a methoxynitrile as well as a dimethoxy compound (Scheme 57). Cyanide competes for the primary cation radical but not for the secondary cations so that the product always contains at least one methoxy group. On a platinum electrode the cis-trans ratio in the methoxynitrile fraction is affected by the substrate concentration and by the addition of aromatic substances suggesting that adsorption on the electrode helps determine the stereochemistry. On a vitreous carbon electrode, which does not strongly adsorb aromatic species, the ratio always approaches the equilibrium value. 

Evans, D.F. (1953). Molecular association of oxygen and aromatic substances. J. Chem. Soc. 345-347... 

For conjugated, non-aromatic substances, both the molar absorptivity and wavelength of maximum absorption increase. An example of this is the comparison of 1-hexene that absorbs at 177 nm with a molar absorptivity of 12,000 while 1,3,5-hexatriene absorbs at 268 nm and has a molar absorptivity of 42,500. 

Partition constant tor the distribution of various aromatic substances (mono-, di-, tri-, and tetramethyl, and chlorobenzenes) between water and an aquifer material (0.15 % organic carbon) as a function of the octanol-water partition coefficient, K<,w. The values of log Kp have been adjusted to be correct for a sorbent of 100 % organic carbon. Kow is defined for the partition of a substance A between octanol water Kow = [A0Ct]/[A(aq)]. 

The property of yielding nitro-derivatives by the action of nitric acid is a characteristic of aromatic substances. According to the conditions under which the nitration is carried out one or more nitro-groups can be introduced. Write the equation for the reaction. 

Charcoal and Activated Carbon Tiselius used charcoal for the frontal analysis of sugars, amino acids and other substances. Charcoal absorbs strongly aromatic substances, such as amino acids, which may be explained by virtue of the fact that the carbon-carbon spacings in graphite are almost of the same order as those present in benzene. Charcoal is also employed for the adsorption of fatty acids. 

Comparison with the general equation (3) for aprotoly ticreactionshows that this equation corresponds to Bronsted s definition if the aromatic substance is accorded a basic character. The proton addition complex ... 

In the ternary systems aromatic substance (A)-Lewis acid (MX3)-hydrogen halide (HX) the formation of a proton addition complex can be formulated analogously. 

N.M.R. Spectra and exchange processes The fact that aromatic substances are relatively weak bases always requires the use of strong acids. However, proton exchange processes take place in such media, and these can interfere to an extraordinary extent with this particular method of measurement. 

The use of N.M.R. spectroscopy further requires that the proton affinity of the aromatic substances should not be too low. Benzene and toluene, for instance, have such a low proton affinity that no proton addition complex has so far been demonstrated by means of N.M.R. spectroscopy, even at — 100°C. A combination with other methods is therefore required in order to demonstrate proton addition complexes in these cases. 

Correlation of the bands which occur in the range 670-900 om i to the number of mutually adjacent H-atoms in the ternary complex aromatic substance-GaCls-HCl... 

---