Aromatic hydrocarbons, alkyl substituted

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). 

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... 

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. 

The radical cations initially formed during the direct oxidation of hydrocarbons [Eq. (1)] are highly reactive species, and their formation is usually followed by a fast reaction in solution. This involves typically a nucleophile (Nu or NuH) or a base (B), resulting in the formation of either an addition product, I, or an elimination product, II, as illustrated by Eqs. (2) and (3). Reaction (2) may be observed for almost any radical cation when a suitable nucleophile is present, whereas reaction (3) is typically observed for alkyl-substituted aromatic hydrocarbons having at least one hydrogen atom in an a position. Other common follow-up reactions are dimerization [Eq. (4)] and the coupling of a radical cation and a molecule of substrate [Eq. (5)]. The neutral molecule in Eq. (5) may also be a hydrocarbon different from R-H ... 

Representative couplings of aromatic hydrocarbons are summarized in Table 1. Alkyl-substituted aromatic hydrocarbons can be coupled to diphenyls and/or diphenylmethanes depending on their substitution pattern (Table 1, numbers 1-6). The initially formed radical cation I [Eq. (3)] reacts with the starting compound to the diphenyl (II) (Eq. (3), path a] or loses a proton to form a benzyl radical [Eq. (3), path b], which after oxidation to the cation undergoes an electrophilic aromatic substitution at the starting compound to form the diphenylmethane (III). A low charge density on an unsubstituted carbon atom of I favors path a, whereas a low charge density on a substituted carbon atom favors path b[4]. 

Introduction. The principle of the method used for the preparation of ethylbenzene is discussed in the introduction to Experiment 10. A mixture of aryl and alkyl halides, when treated with sodium under anhydrous conditions, forms alkyl-substituted aromatic hydrocarbons ... 

The aromatic-OH radical reaction proceeds via two pathways (a) a minor one (of order 10%) involving H-atom abstraction from C—H bonds of, for benzene, the aromatic ring, or for alkyl-substituted aromatic hydrocarbons, the alkyl-substituent groups and (b) a major reaction pathway (of order 90%) involving OH radical addition to the aromatic ring. For example, for toluene these reaction pathways are ... 

As noted above, this H-atom abstraction pathway is minor, accounting for <10% of the overall OH radical reaction for benzene and the alkyl-substituted aromatic hydrocarbons. 

Klemm et al. 36) have claimed that alkyl-substituted aromatic hydrocarbons also exhibit steric hindrance to adsorption the adsorption energy of the aromatic ring decreases as the attached alkyl groups become more bulky. Unfortunately, such an effect—if real—is rather small, and it cannot be distinguished easily from differences in the Q° value of the alkyl group per se. 

From the alkyl-substituted aromatic hydrocarbon with potassium permanganate in sodium hydroxide or sodium carbonate solution... 

PETROLEUM PITCH is a residue from heat treatment and distillation of petroleum fractions. It is a solid at room temperature, consists of a complex mixture of numerous, predominantly aromatic and alkyl substituted aromatic hydrocarbons, and exhibits a broad softening range instead of a defined melting temperature. 

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