Hydrocarbons, alkylating agents

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

In the presence of tellurium tetrachloride, aromatic hydrocarbons are alkylated with reactive alkylating agents such as benzylic or t-butyl alcohols and chlorides. The yields are high with toluene but only moderate for benzene, p-xylene and anisole. Equivalent and catalytic amounts of tellurium tetrachloride, respectively, are required for the alcohols and... 

The mechanism of the photochemical alkylation shows particular characteristics as regards the formation of alkyl radicals, the reaction of these radicals with the heteroaromatic substrates, and the rearomatization of the intermediate products. A variety of alkylating agents (hydrocarbons, alcohols, amines, carboxylic acids, amino acids) have been used for photochemical and y-ray-induced alkylation. " ... 

The side chain alkylation of alkyl benzenes is usually performed with alkenes as alkylating agents in the presence of strong-acid catalysts (256,257). The use of highly basic catalysts such as alkali metals, their hydrides, and sodium and potassium complexes for alkylation of alkylaromatic hydrocarbons has also been reported (256,257). The reaction mechanism proposed by Pines et al. (258) involves the addition of a benzylic carboanion to the alkene (Scheme 41). 

Preparative use could be made also from the perturbed redox catalysis (Eqs. (84)—(86), (93)-(95). For example, alkylated aromatic hydrocarbons that are difficult to obtain by Friedel-Crafts alkylation could be synthesized in this way. The most suitable alkylating agent is tert-butyl chloride or bromide -ass) alkyla-... 

Alkylation with Alkanes. Alkylation of aromatic hydrocarbons with alkanes, although possible, is more difficult than with other alkylating agents (alkyl halides, alkenes, alcohols, etc.).178 This is due to the unfavorable thermodynamics of the reaction in which hydrogen must be oxidatively removed. 

Hydrocarbons with suitably acidic (allylic, benzylic, propargylic, acetylenic) hydrogens can be transformed to organometallic derivatives, which then can react with alkylating agents to yield alkylated products. 

Alkylation is a very broad reaction type and it can, depending on the nature of the alkylating agent, proceed either as a substitution or as an addition reaction. The alkylation by substitution of, for example, aromatic hydrocarbons, phenols or amines is based on the reaction with alkyl halides or alcohols. Some evidence indicates that, at least partly, the alkylation proceeds through the intermediate formation of alkenes from the alkylating agent when the reaction is conducted at atmospheric pressure and at high temperature. 

Satisfactory results were obtained in the Nafion-H-catalyzed gas-phase alkylation of aromatic hydrocarbons with alkyl halides235 [Eq. (5.88)]. Alkylhalides are reactive Friedel-Crafts alkylating agents and give high conversions when alkylating benzene in the gas phase over Nafion-H catalyst. For example, in the alkylation of benzene with isopropyl chloride, conversions as high as 87% were achieved (Table 5.17, run 11). Conversions, however, were temperature and contact time dependent (Table 5.17). 

Some toxicants are known to affect the female reproductive system and processes. Exposure to the alkylating agents cyclophosphamide and vincristine can lead to loss of female sexual function. Cyclophosphamide may attack and damage the oocytes, cells that lead to egg formation. Pharmaceutical busulfan damages ovaries. The 7,8-diol-9,10-epoxide of benzo(a)pyrene, as well as some other metabolites of polycyclic aromatic hydrocarbons, can be toxic to oocytes. 

Cationic surfactants are prepared by the reaction of a tertiary amine with an alkylating agent resulting in the formation of the positively charged nitrogen center. This reaction can be accomplished with a variety of agents as shown in Table 6.1, where each R represents a hydrocarbon residue. 

If Isobutene (or commercial b.b.f.) was used as alkylating agent, up to 40% of heavy hydrocarbons (Cg and higher) were formed, as a result of an Increased tendency to polymerize the Isobutene. 

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