Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/02—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation
  • C07C5/10—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of aromatic six-membered rings
  • C07C5/11—Partial hydrogenation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2601/00—Systems containing only non-condensed rings
  • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
  • C07C2601/16—Systems containing only non-condensed rings with a six-membered ring the ring being unsaturated

Definitions

• This invention relates to a process for the partial reduction of aromatic compounds. More particularly, it relates to an improved process for the production of cyclohexenes by partial reduction of corresponding benzenes.
• the aromatic reactants suitably employed in the process of the invention are mononuclear aromatic hydrocarbons containing a single six-membered aromatic ring.
• Suitable aromatic hydrocarbons contain from 6 to 20 carbon atoms and are characterized as benzene and aliphatic hydrocarbyl-substituted benzene.
• aliphatic hydrocarbyl substituents which contain carbon-carbon unsaturation are in part. operable, such unsaturation is customarily hydrogenated during the course of the reaction and no advantage is gained by utilization of benzenes containing side-chain unsaturation. Best results are obtained when the aliphatic hydrocarbyl substituents are alkyl, including cycloalkyl, having from 1 to 14 carbon atoms.
• preferred aromatic hydrocarbon reactants are unsubstituted benzene or benzene substituted with from 1 to 3 alkyl substituents.
• the preferred aromatic reactants are therefore characterized as nonto tri-alkylbenzene having from 6 to 20 carbon atoms wherein any alkyl substituent(s) are alkyl, including cycloalkyl, of from 1 to 14 carbon atoms.
• Illustrative of such preferred reactants are benzene, toluene, ethylbenzene, cumene, tert-butylben- 3,308,178 Patented Mar.
• acyclic alkyl substituents are preferred over analogous cycloalkyl substituents, and especially preferred is nonto mono-alkylbenzene wherein any alkyl is acyclic alkyl of from 1 to 4 carbon atoms.
• Tetralin which is herein considered to be within the contemplated scope of the dialkylbenzenes of the invention, thereby adding the proviso that when the nonto tri-alkylbenzene is 1,2-dialkylbenzene, the alkyl moieties may together form a divalent alkylene moiety having 4 carbon atoms.
• the alkali metal employed in the process of the invention is a member of Group I of the Periodic Table having an atomic number from 19 to 37, that is, potassium or rubidium. While it is known that lithium will afford similar reduction of the aromatic reactant, sodium or cesium are not suitable in the amine solvents utilized, these metals leading to limited or no conversion of the aromatic reactant. Largely for economic reasons, the use of potassium is preferred over an analogous utilization of rubidium.
• the alkali metal reacts directly with the aromatic reactant to produce a mono-metal derivative, e.g., a benzene free-radical anion, which subsequently reacts with the solvent to introduce hydrogen into the aromatic ring. Subsequent additional reactions result in the formation of the desired cyclohexene product.
• a mono-metal derivative e.g., a benzene free-radical anion
• the alkali metal is preferably employed in amounts equivalent to or in excess over the amount of aromatic reactant, although lesser amounts of alkali metal may be employed if complete conversion of the aromatic reactant is not required.
• ratios of gram-atoms of alkali metal to moles of aromatic reactant from about 2:1 to about 10:1 are suitable, however, ratios of gram-atoms of alkali metal to moles of aromatic reactant from about 4:1 to about 8:1 are preferred.
• the alkali metal of atomic number from 19 to 37 is employed as a pure substance or as a mixture or alloy with the other member of the class. Mixtures of potassium and rubidium in all proportions are suitable. Rather unexpectedly, it has been found that mixtures of alkali metal of atomic number from 19 to 37 with alkali metals that are unsuitable when utilized singly exhibit power to reduce the aromatic reactant beyond that calculated for the amount of alkali metal of atomic number from 19 to 37 present in the mixture.
• mixtures of singly suitable alkali metal e.g., potassium or rubidium
• singly unsuitable alkali metal e.g., sodium or cesium
• such mixtures may contain any convenient proportion of singly suitable and singly unsuitable alkali metals.
• amounts of such mixture be employed sufficient to provide at least one gram-atom of alkali metal of atomic number from 19 to 37 for each mole of aromatic compound utilized.
• ratios of gram-atoms of total alkali metal to moles of aromatic reactant having an atomic number from 11 to 55 from about 2:1 to about 10:1 are satisfactory, provided that the mixture contain at least 1 gram-atom of alkali metal having an atomic number from 19 to 37 for each mole of the aromatic reactant employed.
• the process of the invention is conducted by contacting the nonto tri-alkylbenzene with alkali metal in the presence of a liquid aliphatic amine.
• aliphatic secondary amines and aliphatic poly(primary amines) are in part operable, best results are obtained when the amine is an aliphatic primary amine, particularly a lower alkylamine of from 1 to 4 carbon atoms as exemplified by methylamine, ethylamine, n-propylamine, n-butylamine, isopropylamine, sec-butylamine and isobutylamine.
• the amine is an n-alkylamine, particularly n-alkylamine of from 1 to 2 carbon atoms, i.e., methylamine and ethylamine.
• the amine employed in the process of the invention appears to serve several functions.
• the amines serve as a solvent for the organic and inorganic reactants, and also serves as a source of the hydrogen introduced onto the benzene ring of the aromatic reactant.
• the use of an amine provides a substantial advantage for the present process over similar processes of the prior art. Certain of these processes, e.g., that of US. 2,182,242, employ reaction systems containing hydroxylic components, e.g., water or alcohol.
• the alkali metal-containing product is the hydroxide or alkoxide from which the alkali metal is not easily regenerated.
• the efiective loss of alkali metal precludes economical utilization of these processes on a commercial basis.
• the alkali metal product is an amide, e.g., from the reaction of potassium in methylamine is obtained potassium methamide.
• the alkali metal is recovered as by amine exchange with ammonia to produce alkali metal amide, e.g., potassium amide, followed by hydrogenation of the amide to the corresponding alkali metal hydride and pyrolysis of the hydride to liberate the elemental alkali metal.
• molar ratios of amine to the aromatic reactant from about 7:1 to about 50:1 are generally satisfactory, although molar ratios of amine solvent to aromatic reactant from about 12:1 to about 30:1 are preferred.
• the amine is preferably employed in a form substantially free of hydroxylic materials, e.g., water, alcohol, or carboxylic acid, which result in the recovery of alkali metal in the form of undesirable by-products.
• hydroxylic materials e.g., water, alcohol, or carboxylic acid
• the solvent employed is preferably free from hydroxylic compound.
• solvent is provided as a mixture of amine with a limited amount of ammonia.
• the presence of substantial quantities of ammonia in the reaction solvent has a deleterious effect on the process of the invention through lowering of the reaction rate, lowering of product yield when alkylated benzenes are employed as the aromatic reactant, and promotion of an undesirable isomer distribution of alkylated cyclohexene produced by reduction of such alkylated benzenes.
• the molar amount of ammonia to be employed in a solvent comprising a mixture of amine and limited ammonia is preferably not greater than three times the gram-atomic amount of alkali metal present in the reaction system, and best results are obtained when the molar ratio of any ammonia present to alkali metal is substantially stoichiometric, that is, a molar ratio of about 1:1.
• the solvent employed in the present process therefore comprises alkylamine optionally containing ammonia.
• alkylamine optionally containing ammonia.
• amounts of ammonia up to about 40% mole based upon total solvent are suitable, although amounts of ammonia up to about 25 %v mole on the same basis are preferred.
• the process of the invention is operable in the presence of inert diluents such as saturated hydrocarbons, e.g., hexene, heptene, cyclohexane and the like.
• inert diluents such as saturated hydrocarbons, e.g., hexene, heptene, cyclohexane and the like.
• saturated hydrocarbons e.g., hexene, heptene, cyclohexane and the like.
• the process is conducted at a somewhat elevated temperature.
• the advantages of utilization of an amine solvent are illustrated by a lowered temperature requirement when compared to processes wherein ammonia is employed as the sole solvent.
• Suitable reaction temperatures are from about 15 C. to about 110 C., with the temperature range from about 20 C. to about 100 C. being generally preferred, and the temperature range from about 30 C. to about C. being particularly satisfactory.
• the reaction is conducted at pressures which are atmospheric, subatmospheric or superatmospheric as long as the reactants are maintained substantially in the liquid phase. Typical reaction pressures vary from about 5 atmospheres to about 50 atmospheres although reaction pressures from about 10 atmospheres to about 40- atmos pheres are most customary.
• the product mixture is separated and the desired cyclohexene product is recovered by conventional means such as fractional distillation, selective extraction, crystallization and the like.
• the product of the present process is a nonto trialkylcyclohexene illustratively produced by the addition of four atoms of hydrogen to the aromatic ring of the nonto tri-alkylbenzene as previously defined.
• cyclohexene from reaction of benzene is obtained cyclohexene, and from toluene is obtained a mixture of l-methylcyclohexene, B-methylcyclohexene, and 4-methylcyclohexene.
• a particular advantage of the present process lies in the favorable isomer distribution resulting from the reduction of alkylbenzenes thereby.
• l-methylcyclo hexene is a most desirable isomer resulting from toluene reduction, due to the known pyrolyzability of this isomer to ethylene and isoprene. From reductions employing lithium and amine, the percentage of l-methyl isomer observed in the product mixture approximates 65%. However, by the present the selectivity toward production of the l-methylcyclohexene isomer is often over The cyclohexene products of the inevntion are useful as chemical intermediates.
• the non-alkyl product, cyclohexene is a chemical of commerce and has particular utilization as a precursor for a,w-dicarboxylic acids, w'ami' nocarboxylic acids, polyesters, polyamides and the like.
• alkyl is acyclic alkyl of from 1 to 4 carbon atoms with TABLE VI Alkylbenzene Metal Temp, Time, Conversion of Selectivity 0. Hrs.
• nonto tribenzene is nonto mono-alkylbenzene wherein any alkyl is acyclic alkyl of from 1 to 4 carbon atoms.
• any alkyl is acyclic alkyl of from 1 to 4 carbon atoms with from about 4 gram-atoms to about '8 gram-atoms per mole of said nonto mono-alkylbenzene of alkali metal of atomic number from 19 to 37, in from about 7 moles to about 50 moles per mole of said nonto mono-alkylbenzene of alkylamine of from 1 to 2 carbon atoms, in the liquid phase at a temperature from about 30 C to about C.
• alkylcyclohexene by intimately contacting alkylbenzene wherein the alkyl is acyclic alkyl of from 1 to 4 carbon atoms, with from about 4 gram-atoms to about 8 gram-atoms per mole of alkylbenzene of potassium, in from about 7 moles to about 50 5 moles per mole of alkylbenzene of alkylarnine of from 1 to 2 carbon atoms, in the liquid phase at a temperature from about 30 C. to about 80 C.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Citations (3)

• 1964
  • 1964-12-17 US US419195A patent/US3308178A/en not_active Expired - Lifetime
• 1965
  • 1965-12-15 DE DE19651493131 patent/DE1493131A1/de active Pending
  • 1965-12-15 NL NL6516332A patent/NL6516332A/xx unknown
  • 1965-12-15 BE BE673784D patent/BE673784A/xx unknown
  • 1965-12-15 GB GB53233/65A patent/GB1091010A/en not_active Expired
  • 1965-12-15 FR FR42320A patent/FR1459629A/fr not_active Expired

Patent Citations (3)

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