Alkylnaphthalenes isomerization

Nevertheless, a number of gas chromatographic applications exist, epecially those for the determination of crude oil indicators. Such indicators are used as geochemical parameters for the thermal history of the crude as well as to indicate the possible relationship between crudes from different wells. These indicators comprise a number of isomeric aromatic species, such as the individual alkylnaphthalenes (44, 45), the individual Cio-mono-aromatics or the individual C9-mono-aromatics. The ratio between these isomers gives a definite indication of the crude oil. In general, these systems use a Deans switching unit to make a heart-cut, which then is focused, reinjected and separated on a second column with a different polarity. 

Studies of Lewis acid-catalyzed isomerization of alkylnaphthalenes were carried out by Olah and Olah in connection with alkylation of naphthalene with alkyl halides.88 Methyl-, ethyl-, isopropyl- and ferf-butylnaphthalene readily undergo isomerization with A1C13 in CS2 solution. The rate of isomerization and the equilibrium concentration of the p isomer were found to increase with increasing branching of the alkyl substituent (Table 4.3). 

Alkylation with isobutylene under similar conditions167 and alkylation with propylene catalyzed by perfluorosulfonic acids,168 in turn, lead to 2-substituted naphthalenes. As was shown by Olah and Olah,169 the kinetic alkylation of naphthalene, even in case of rm-butylation, gives preferentially the 1-isomers, which, however, isomerize very fast to the thermodynamically preferred 2-alkylnaphthalenes. Great care is therefore needed to evaluate kinetic regioselectivities. 

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