Patent GB-740978-A (GB)
Title: Catalytic alkylation of carbocyclic hydrocarbons
IPC: C07C2/72
Filed: 1952-10-16
Abstract: A hydrogen-bearing saturated carbon atom alpha to a doubly-bonded nuclear carbon atom in a carbocyclic hydrocarbon is alkylated by reacting the carbocyclic hydrocarbon with a non-conjugated olefin as alkylating agent in the presence of an organo-alkali metal compound as catalyst at a pressure of not more than 90 atmospheres.  The carbon atom to be alkylated can be either cyclic in its bonding as in alicyclic and hydroaromatic compounds, e.g. cyclohexene, 1 - cyclohexylcyclohexene, cyclopentene, tetrahydronaphthalene, hydrindene, 1-tert - butylcyclohexene, 1 - phenylcyclohexene, and 4-methyl- (or ethyl-) cyclopentene, or it may be acyclic in its bonding as in aromatic compounds such as toluene, diphenylmethane, n-butylbenzene, ethylbenzene, n-propylbenzene, i-propylbenzene, sec.-butylbenzene, di-n-propylbenzenes, n-dodecylbenzene, xylene, trimethylbenzenes, and alpha-methylnaphthalene.  Alicyclic compounds having substituent groups on a doubly bonded nuclear carbon atom can alkylate on either an acyclic or cyclic carbon atom or both.  Such compounds include 1-methyl- (or ethyl-) cyclohexene-1, 1,2-dimethylcyclohexene, 5-methyl-1,2,3,4-tetrahydronaphthalene, 5 - n - propyl - 1,2,3,4 - tetrahydronaphthalene, 1 - methylcyclopentene, 5-methylhydrindene and 1,2-dimethylcyclopentene.  In compounds having two or more hydrogen-bearing saturated carbon atoms alpha to a nuclear double bond in which the alpha carbon atoms are attached to a different number of hydrogen atoms, alkylation will preferably occur first on the carbon atom containing the greater number of hydrogen atoms, thus in p-cymene the methyl group is alkylated before the alpha-carbon atom of the isopropyl group. Other compounds of this type include methyl ethyl-, dimethylethyl-, methylpropyl-, and dimethylpropylbenzenes, and 1-methylcyclohexene.  Other materials which may be alkylated include the isomeric diethylbenzenes, 9,10-dihydrophenanthrene, 2-phenyldodecane, and p - methyl - tert. - butylbenzene. Specified alkylating agents are acyclic monolefins, e.g. ethylene, propylene, butene-1 (or -2), pentene-1 (or -2), hexene-1 (-2) or (-3), heptenes, octenes, nonenes, decenes, undecenes, dodecenes, isobutylene 3-methyl-heptene-1, 2-ethylpentene-1, 3-methyl-hexene-3, pentadecenes and tetradecenes. Other olefins specified are cyclic olefines, and non-conjugated polyolefines, e.g. cyclohexene, cyclopentene, 1,4-cyclohexadiene, 1,5-hexadiene, and 1,4-hexadiene.  The organoalkali metal compounds used are those in which the alkali metal is bonded to a carbon atom in the organic molecule and include hydrocarbon alkali metal compounds, sodium derivatives of heterocyclic nitrogen compounds and sodium derivatives of tertiary amines.  Examples include alkali metal derivatives of toluene, of p-methyl-N,N-dimethylaniline, of quinoline and of acridine.  The alkali metal may be sodium, potassium, lithium, caesium, or rubidium, but is preferably sodium or potassium. Preferred catalysts are alkyl-alkali metal compounds such as amyl sodium, butyl sodium, hexyl potassium, aryl-alkali metal compounds such as phenyl sodium, p-tolyl potassium, phenyl lithium, and alkylaryl-alkali metal compounds such as benzyl potassium, benzyl sodium, and cumyl sodium. Mixtures of organo-alkali metal compounds can also be used.  The amount of catalyst should generally be about 0.01 to 10 per cent of the weight of carbocyclic compound.  The reaction is operable at 0-350 DEG  C., preferably at 100-200 DEG  C., and is preferably operated at above 15 atmospheres pressure and either or both of the reactants may be dissolved in an inert solvent, e.g. a paraffin, cycloparaffin or an aromatic containing no hydrogen - bearing carbon atom alpha to the aromatic nucleus.  Specified solvents are n-octane, iso-octane, cyclohexane, benzene, tert.-amyl benzene, and tert.-heptyl benzene.  The process may be carried out in a continuous manner, e.g. by passing the reactants in the liquid or vapour state over a fixed bed of catalyst which may be admixed with an inert carrier.  Alternatively the liquid or liquid-vapour reaction can be carried out in the presence of a suspended catalyst which is transported through the reaction zone by the velocity of liquid reactants and products.  In the vapour-phase reaction the fluidized bed technique can be used. The reactants can be diluted with inert gases such as propane, ethane, methane, nitrogen, helium or neon. Detailed examples are given for the alkylation of toluene with ethylene, using benzyl sodium as catalyst, to form n-propyl benzene together with some 3-phenyl pentane and tert.-heptyl benzene; of toluene with ethylene using benzyl potassium as catalyst to form n-propyl benzene and 3-phenyl pentane; of cumene with ethylene in the presence of cumyl sodium as catalyst to form tert.-amyl benzene; of cyclohexene with ethylene in the presence of amyl sodium as catalyst to yield 3-ethylcyclohexene; of trimethyl benzenes with ethylene in the presence of dimethyl benzyl sodium to form a mixture of dimethyl n-propyl benzenes; and of toluene with propylene in the presence of benzyl sodium as catalyst to yield isobutyl benzene.  Reference is also made to the alkylation of xylenes, isopropyl benzenes, tetrahydronaphthalene, cyclohexene, diphenyl methane, p - cymene, alpha-methyl naphthalene, sec.-butyl benzene, a  - isopropylnaphthalene, 1 - methyl - 1,2,3,4 - tetrahydronaphthalene, 1,4 - dimethyl - 1,2,3,4-tetrahydronaphthalene and diisopropyl benzene respectively with ethylene as alkylating agent and the various products formed are specified.  The alkylation of toluene with butene-2, hexene-1, dodecene-1 to yield 2-benzyl butane, 2-benzyl hexane and 2-benzyl dodecane is also referred to.