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Aromatic hydrocarbons photochemical reactions

Hashimoto, S. and Akimoto, H. (1989). UV absorption spectra and photochemical reactions of simple aromatic hydrocarbons in the cryogenic oxygen matrix. J. Phys. [Pg.267]

Nitrobenzenes react with potassium cyanide in the presence of cetyltrimethylammo-nium bromide to yield benzonitriles [71], The reaction also requires the presence of chloro substituents on the ring and at least two nitro groups (Table 2.9). Diazosulphides, ArN=NSPh, are converted into the benzonitriles, ArCN, by a photochemically induced SRN1 reaction with tetra-n-butylammonium cyanide [72, 73], Yields vary from <20% to >70%. Photocyanation of aromatic hydrocarbons has been achieved using tetra-n-butylammonium cyanide in acetonitrile or dichloromethane [74, 75]. [Pg.41]

Particular attention has been focused on the toxic effects of aromatic hydrocarbons because these chemicals have proven highly carcinogenic to humans and marine life. Of greatest concern are the PAHs, which are toxic to the benthos at the ppb level. The most common compounds are shown in Figure 28.20 their structures are based on fused aromatic rings. These high-molecular-weight compoimds are very nonpolar and, hence, have low solubilities. Once in seawater, they tend to adsorb onto particles and become incorporated in the sediments. The toxicity of PAHs is enhanced by photochemical reaction with UV radiation. Photo-activated toxicity is especially problematic in shallow-water sediments, such as found in estuaries. [Pg.805]

Organic aerosols formed by gas-phase photochemical reactions of hydrocarbons, ozone, and nitrogen oxides have been identified recently in both urban and rural atmospheres. Aliphatic organic nitrates, such dicarboxylic acids as adipic and glutaric acids, carboxylic acids derived from aromatic hydrocarbons (benzoic and phenylacetic acids) and from terpenes emitted by vegetation, such as pinonic acid from a pinene, have been identified. The most important contribution in this held has been that of Schuetzle et al., who used computer-controlled... [Pg.48]

Kanno, S. and Nojima, K. Studies on photochemistry of aromatic hydrocarbons. V. Photochemical reaction of chlorobenzene with nitrogen oxides in air, Chemosphere, 8(4) 225-232, 1979. [Pg.1676]

Ghe, T. Mutagenicity of photochemical reaction products of polycyclic aromatic hydrocarbons with nitrite, Sci. Total Environ., 39(1/2) 161-175, 1984. [Pg.1704]

Additions to Aromatic Hydrocarbons. A variety of photochemical additions to aromatic hydrocarbons have been reported. Benzene and its derivatives add to maleic anhydride74-76 as well as to simple olefins,77-80 isoprene,81 acetylene derivatives,79,82 and alcohols.83 The mechanism of the maleic anhydride-benzene reaction is discussed in Section IV. A.4. Naphthalene forms a photoadduct with dimethyl acetylenedicarboxylate62 and with acrylonitrile8211 while anthracene behaves similarly with maleic anhydride84 and with 1,2-benzanthracene.85 The photoaddition of several aromatic amines to anthracene has been reported to proceed via a charge transfer complex86,87 in fact, the majority of these addition reactions may proceed in this manner. [Pg.257]

Radical cations can be formed by irradiation of unsubstttuted aromatic hydrocarbons such as naphthalene, and this makes possible the photochemical displacement of hydride ion by a nucleophile such ascyanide f3.10). Oxygen is not necessary for the success of this type of reaction if a good electron-acceptor is present, such as p-dicyanobenzene (3.11), which enhances the initial photoionization and also provides for reaction with the displaced hydrogen. [Pg.81]

Mason and Smith (1969) found that for a series of mono- and bicyclic aromatic hydrocarbons the changes in the fluorescence spectrum with acidity reflected the ground state protonation reaction. The p Sj )-values calculated for benzene, toluene, naphthalene, azulene, and indolizine do not correspond to observable processes since the rate of protonation is too slow to compete with deactivation of the Sj state. Photochemical deuterium and tritium exchange experiments in 1 mole dm-3 perchloric acid indicate that the radiative deactivation rate of an electronically excited aromatic hydrocarbon is faster than the rate of protonation by a factor >10s. [Pg.204]

The reactions observed in the photochemical smog, especially those concerning decomposition and oxidation of volatile organic substances, are accelerated by atmospheric aerosols, eg oxidation of some halogenated hydrocarbons, isoprene, monoterpenes, and aromatic hydrocarbons is enhanced by the surfaces of metal oxides, desert sand, volcanic ash, and sea salt [8],... [Pg.138]

Photoinitiated electron transfer reactions are among the earliest photochemical reactions documented in the chemical literature and (ground state) electron donor-acceptor interactions have been known for over one hundred years. Some aspects of plant photosynthesis were already known to Priestly in the eighteenth century. The photooxidation of oxalic acid by metal ions in aqueous solution was discovered by Seekamp (UVI) in 1803 and by Dobereiner (Fe,n) in 1830. The electron donor-acceptor interactions between aromatic hydrocarbons and picric acid were noticed by Fritzsche in the 1850s the quinhydrones are even older,... [Pg.2]

Photochemical electron transfer reactions of electron donor-acceptor pairs in polar solvents provide a convenient and effective method for the generation of radical cations which can be trapped by complex metal hydrides. One of the most effective systems is based on irradiation of a solution of substrate, sodium borohydride and 1,4- or 1,3-dicyanobenzene. A range of bi- and poly-cyclic aromatic hydrocarbons has been converted into the dihydro derivatives in this way. An especially important aspect of this route to dihydroaromatic compounds is that it may give access to products which are regioisomeric with the standard Birch reduction products. Thus, o-xylene is converted into the 1,4-dihydro product (229) rather than the normal 3,6-dihydro isomer (228). The m- and p-xylenes are similarly reduced to (230) and (231), respectively. ... [Pg.517]

The largest sink for alkanes in the atmosphere is reaction with OH and NO3 radicals. The formation of photochemical smog is described in detail in (Chapter 9.11, Sillman). Mono-aromatic hydrocarbons react only slowly with O3 and NO3 radicals in the troposphere. The only important atmospheric processes for mono-aromatic hydrocarbons, and naphthalene and dinaphthalenes are reactions with OH radicals (Atkinson, 1990). The products of these reactions include aldehydes, cresols, and, in the presence of NO, benzylnitrates. Methane can be an important contributor to ozone formation, especially in the remote troposphere, as described in (Chapter 9.11, Sillman). [Pg.4991]

Many common solvents are usually considered to be inert in photochemical reactions. Only few solvents,such as alcohols and paraffinic hydrocarbons are indeed inert when irradiated in the range of 200-700 nm. Other solvents,such as ketones,aromatic hydrocarbons,tetrahydrofurane,chloroform and carbon tetrachloride are in this range photolysed (3). [Pg.256]


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See also in sourсe #XX -- [ Pg.378 , Pg.386 , Pg.403 ]




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