Alkyl benzenes halogenation

Secondary alkyl halides react by a similar mechanism involving attack on benzene by a secondary carbocation Methyl and ethyl halides do not form carbocations when treated with aluminum chloride but do alkylate benzene under Friedel-Crafts conditions The aluminum chloride complexes of methyl and ethyl halides contain highly polarized carbon-halogen bonds and these complexes are the electrophilic species that react with benzene... 

The equilibrium concentrations of many disubstituted benzenes (containing alkyl and halogen substituents) show that the meta isomer is in nearly all cases the most thermodynamically stable. It is not obvious why this should be so. Shine182 had discussed this problem in terms of the relative sizes of the standard enthalpy and entropy changes between any pair of isomers. 

The alkylation of halogen-substituted benzenes such as fluorobenzene and dichlorobenzenes with other (dichloroalkyl)silanes in the presence of aluminum chloride catalyst afforded isomeric mixtures of the corresponding (dihalogen-substituted phenyl)alkylsilanes in moderate yields (Eq. (13)). These results are summarized in Table Xll. 

Figure 6.8 Relationship of enthalpy to log k values. Column, ODS silica, ERC-ODS, 15 cm x 6.0 mm i.d. eluent, 80% aqueous acetonitrile at 30 °C. Numbers beside symbols see Table 6.4. O, Polycyclic aromatic hydrocarbons x, alkyl-benzenes, O, halogenated benzenes A, alkanols and , alkanes.

Simple benzene derivatives show most of the characteristics of benzene, including the moderate band in the 210-nm region and the benzenoid band in the 260-nm region. Alkyl and halogen substituents increase the values of Amax by about 5 nm, as shown by the examples in Table 16-2. An additional conjugated double bond can increase the value of Amax by about 30 nm, as shown by the UV spectrum of styrene in Figure 16-19. 

On heating in polyphosphoric acid 1-phenylthiosemicarbazides with alkyl or halogen substituent in the benzene ring turn into 2-aminobenzothiazoles in good yield (Scheme 2.101) [578],... 

Nitro-alkyl Benzenes.—-Isomeric with nitro toluene we have nitro-methyl benzene, CeHs—CH2NO2, which belongs to the group of nitro substitution products in which nitration takes place in the paraffin side-chain and not in the benzene ring. It must be formed, therefore, not by direct nitration, but by reaction between a halogen-alkyl benzene and silver nitrite. 

When polyalkyl- or polyhalobenzenes are treated with sulfuric acid, the ring is sulfonated, but rearrangement also takes place. The reaction, known as the Jacobsen reaction, is limited to benzene rings that have at least four substituents, which can be any combination of alkyl and halogen groups, where the alkyl groups can be... 

Aryl amine intermediates for azo and triphenylmethane dyes, as well as a number of vat dye (anthraquinone) intermediates, are made from compounds such as benzene, alkyl benzenes (toluene and higher homologues), phenol and naphthalene. A limited number of reactions are used to produce the most important dye intermediates, including nitration, reduction, halogenation, sulfonation, /V-alkylation, /V-acylation and alkali fusion33,34. 

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