Alkyl-substituted aromatic

Alkyl-Hyd.roxyla.tion. This is commonly observed as the initial transformation of alkyl-substituted aromatic pesticides such as alachlor [15972-60-8] and metolachlor [51218-45-2] (eq. 2) (2) (16). These reactions are typically catalyzed by relatively nonspecific oxidases found in fungi and actinomycetes. 

Medium reactivity contaminants alcohols, ketones, organic acids, esters, alkyl-substituted aromatics, nitro-substituted aromatics, carbohydrates. 

Relative intensities are measured on the basis of peak integration of the alkyl-substituted aromatic carbons shift values from TMS. 

Further isomerization reactions may occur with alkyl-substituted aromatic reaction products, and a considerable study has been made of the reactions of this type of molecule. The following are the main types of skeletal reactions involving alkyl substituents on an aromatic ring (a) If the substituent chain is sufficiently large, there may occur within it all of the processes we have already discussed for aliphatic hydrocarbons them-... 

The Hiyama coupling offers a practical alternative when selectivity and/or availability of other reagents are problematic. Hiyama et al. coupled alkyltrifluorosilane 74 with 2-bromofuran 73 to give the corresponding cross-coupled product 75 in moderate yield in the presence of catalytic Pd(Ph3P)4 and 3 equivalents of TBAF [65]. In this case, more than one equivalent of fluoride ion was needed to form a pentacoordinated silicate. On the other hand, alkyltrifluorosilane 74 was prepared by hydrosilylation of the corresponding terminal olefin with trichlorosilane followed by fluorination with C11F2. This method provides a facile protocol for the synthesis of alkyl-substituted aromatic compounds. 

The hydrogenation of simple alkenes, such as hexene, cyclohexene, cyclo-hexadiene and benzene, has been extensively studied using biphasic, alternative solvent protocols. These hydrocarbon substrates are more difficult to hydrogenate compared to substrates with electron withdrawing groups. Benzene and alkyl substituted aromatic compounds are considerably more difficult to hydrogenate... 

Representative couplings of aromatic hydrocarbons are summarized in Table 10. Alkyl-substituted aromatic hydrocarbons can be coupled to diphenyls and/or diphenylmethanes depending on their substitution pattern (Table 10, numbers 1-6). Reactions occur according to Scheme 9, paths (a) and (c). 

A common feature of any cyclization reaction is that a new intramolecular C—C bond is produced that would not have been formed in the absence of the catalyst. Those reactions in which one ring closure step is sufficient to explain the formation of a given cyclic product will be called simple cyclization processes, although their mechanism is, as a rule, complex. We shall distinguish those cases in which any additional skeletal rearrangement step(s) is (are) required to explain the process. Some specific varieties of hydrocarbon ring closure processes are not included. A recent excellent review deals with the formation of a second ring in an alkyl-substituted aromatic compound (12). Dehydrocyclodimerization reactions have also to be omitted—all the more since it is doubtful whether a metallic function itself is able to catalyze this process (13). 

Campbell, D.R. and Priegnitz, J.W. (1975) Separation of tetra-alkyl substituted aromatic hydrocarbon isomers. U.S. Patent 3,864,416. 

It is known that the oxidation of alkyl-substituted aromatic hydrocarbons in acetic acid on metal bromide catalysis follows the one-electron transfer mechanism (Sheldon and Kochi 1981). The rate-determining stage is the one-electron transfer from the substrate to the metal ion in the highest oxidation state (Digurov et al. 1986). As a result, an unstable cation-radical is formed that... 

Both nitric acid and nitrogen dioxide, in the liquid and vapour phase, have been used for the nitration of the alkyl side chains of various alkyl-substituted aromatics without affecting the aromatic nucleus.Thus, treatment of ethylbenzene with nitric acid of 12.5 % concentration in a sealed tube at 105-108 °C is reported to generate a 44 % yield of phenylnitroethane. The nitration of toluene with nitrogen dioxide at a temperature between 20-95 °C yields a mixture of phenylnitromethane and phenyldinitromethane with the proportion of the latter increasing with reaction temperature. ... 

The solubilities of aromatic compounds in the ionic liquid are dramatically higher than those of saturated compounds. Benzene has a solubility of 4.9mol/mol of ionic liquid, and thiophene has a solubility of 6.7mol/mol of ionic liquid. A dramatic steric effect was observed on the solubility of aromatics the alkyl-substituted aromatics showed reduced solubility. Although the solubility of hexene in the ionic liquid is considerably lower than that of the aromatics, it is still measurably higher than that of hexane. Similar structure-solubility relationships characteristic of organic molecules were observed with the ionic liquids [BMIM]BF4, [BMIM]PFg, and [EMIM]BF4 (Fig. 10) (27). 

In alkyl-substituted aromatic compounds, cleavage is very probable at the bond /3 to the ring, giving the resonance-stabilized benzyl ion or, more likely, the tropylium ion ... 

It can be seen in Fig. 3 that the saturate fraction consists primarily of linear paraffins having between 12 and 25 carbons. The monoaromatic fraction is much more complicated as is the diaromatic fraction. Almost no sulfur species are found in the saturates or monoaromatic fractions. Thus, the sulfur species that must be removed from these fuels are found in multiring aromatic structures. The sulfur-free aromatic fraction was shown to be composed primarily of five classes of alkyl-substituted aromatic ring structures. These are illustrated in Fig. 4, and the individual components are enumerated in Table II. 

Near-quantitative yields of aryl isopropyl carbonates were realized in a similar process when diisopropyl peroxydicarbonate was reacted with alkyl-substituted aromatics.794 Substitution is effected by a radical entity possessing a considerable ionic character. 

Side-Chain Chlorination of Arylalkanes. Alkyl-substituted aromatic compounds can easily be halogenated at the benzylic position with chlorine or bromine.107 108,142 143 a-Monohaloalkylaromatics are usually the main products with both reagents. 

None of the alkyl-substituted aromatics identified as artifact contaminants from XAD-2 resin by USEPA-Battelle were identified in this experiment. 

Table 8. Preparation of Aromatic Carboxylic Acids by the Oxidation of Alkyl-Substituted Aromatics...

Schuchmann MN, Steenken S, Wroblewski J, von Sonntag C (1984) Site of OH radical attack on dihydrouracil and some of its methyl derivatives. Int J Radiat Biol 46 225-232 Schuler RH, Albarran G, Zajicek J, George MV, Fessenden RW, Carmichael I (2002) On the addition of OH radicals to the ipso position of alkyl-substituted aromatics production of 4-hydroxy-4-methyl-2,5-cyclohexadien-1-one in the radiolytic oxidation of p-cresol. J Phys Chem A 106 12178-12183... 

The alkylation of alkyl-substituted aromatic hydrocarbons by propylene and isobutylene described by Pines and Schaap (1960), and the dimerization of olefins with organo-alkali metal compounds, are also found to proceed most easily when primary carbanions are formed since they are more stable than secondary and particularly tertiary carbanions. 

Inaccuracies also arise in melting point estimations for the alkyl substituted aromatic compounds when these molecules display some degree of symmetry. If, for example, the isopropyl groups of p-diisopropylbenzene are considered freely rotating in the crystal,... 

In the case of alkyl-substituted aromatics, the predominant reaction path very often is side-chain acyloxylation. By using Pd-coated cathodes in an undivided cell, it is possible to avoid the formation of the side chain-substituted products, because under these conditions the benzyl ester undergoes cathodic cleavage into the starting compounds 161) ... 

Fig. 17.50. One-pot synthesis of an alkyl-substituted aromatic compound that involves a dissolving lithium reduction of a benzyl alkoxide.

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