Transfer of cycloalkyl groups by transalkylation of aromatics

There is provided a process for transferring cycloalkyl groups from donor to acceptor aromatic molecules. The process involves the use of a Bronsted acid catalyst such as trifluoromethanesulfonic acid.

BACKGROUND 
This invention relates to the transfer of cycloalkyl groups by 
transalkylation of aromatics. 
Transalkylation reactions are a useful means for transferring alkyl groups 
from one aromatic compound to another. In the Farcasiu U.S. Pat. No. 
4,317,712, heavy petroleum oils, such as vacuum resids, and heavy 
fractions of tar sands and shale oil, are partially converted to more 
volatile hydrocarbons by mixing with light aromatic hydrocarbons and 
treatment of the mixture with a Friedel-Crafts catalyst such as aluminum 
chloride. It it believed that the conversion found is essentially a 
transalkylation, i.e. the resid undergoes dealkylation with concurrent 
alkylation of the light aromatic hydrocarbon. In addition to aluminum 
trichloride, trifluoromethanesulfonic acid is also suggested as being a 
suitable catalyst for the process described in U.S. Pat. No. 4,317,712. 
Note column 5, lines 16-19 and Example 8. 
A number of known and useful compounds contain cycloalkyl groups bound to 
an aromatic ring. Examples of such compounds include phenylcyclohexane, 
phenylcyclopentane and dinitrocyclohexylphenol. Accordingly, methods for 
preparing such compounds are needed. 
SUMMARY 
According to one aspect of the invention, there is provided a process for 
transferring alkyl groups from donor compounds to acceptor compounds by a 
transalkylation reaction, said donor compounds being aromatic compounds 
having said alkyl groups substituted on aromatic rings thereof, said 
acceptor compounds being aromatic compounds not having said alkyl groups 
substituted on aromatic rings thereof, said process comprising contacting 
sufficient amounts of said donor and acceptor compounds and a 
catalytically effective amount of a Bronsted acid catalyst such as 
trifluoromethanesulfonic acid under sufficient transalkylating conditions, 
whereby essentially all of said alkyl groups which are transferred are 
cycloalkyl groups, said transfer taking place essentially without 
isomerization of the saturated ring of the cycloalkyl group. The molar 
ratio of donor:acceptor:acid may be, e.g., about 1:2-10:0.2-0.5.

EXAMPLE 
Cycloalkylarenes, more particularly 1-cyclohexylnapthalene and 
9-cyclohexylphenanthrene, respectively, were mixed with ortho-xylene and 
trifluoromethanesulfonic acid in a ratio of 1:10:0.5. More particularly, 
these reactants were mixed at 25.degree. C. in a round-bottomed flask, 
equipped with an immersed thermometer, a reflux condenser topped with a 
drying tube (Drierite) and a magnetic stirring bar. The reactions were 
conducted at 80.degree. C. by heating the flask quickly to that 
temperature, and after that (5-10 min) the first sample was withdrawn. The 
composition at that moment was taken as the starting point for a kinetic 
study. In fact, very little conversion occurred during heating. 
The aliquat samples were quenched in aqueous sodium hydroxide and the 
hydrocarbon phase was isolated and dried (CaSO.sub.4) before analysis. 
Product analysis was accomplished by GLC on a 6'.times.1/2 in OD stainless 
steel column, with 3% OV17 on 80/100 Supelcoport, and by GLC-MS on a 
Hewlett-Packard 5992A instrument, equipped with a 50 m OV-101 SCOT column. 
Results are summarized in FIG. 1. 
Without wishing to be bound by any particular theory, it is noted that the 
transfer of cyclohexyl groups occurs without isomerization of the 
saturated ring. Together with the equality of kinetic order in donor, this 
finding theoretically indicates that the same mechanism operates for the 
transfer of n-alkyl and cycloalkyl groups. On the other hand, partial 
isomerization has been observed in the reaction of sec-alkylbenzenes with 
benzene. Note Burwell, R. L., Jr., Shields, A. D., J. Am. Chem. Soc., 
1955, 77, 2766.