Patented Mar. 10, 1953 2,631,172

UNITED STATES PATENT OFFICE PREPARATION OF ARYL HALOALEKANES Louis Schmering, Riverside, Ill., assignor to Uni versal Oil Products Company, Chicago, Ill., a corporation of Delaware No Drawing. Application January 29, 1948, Serial No. 5,207 3 Claims. (C. 260-651) 2 This invention relates to a process for prepar than three carbon atoms. These aromatic hy ing aryl haloalkanes which also may be referred drocarbon starting materials contain at least to as Chaloalkyl) aromatic hydrocarbons. More One replaceable nuclear hydrogen atom. Naph particularly the process relates to the prepara thalene, alkylnaphthalenes, and other polycyclic tion of monohaloalkyl benzene hydrocarbons aromatic hydrocarbons containing a replaceable containing a halogen selected from the group nuclear hydrogen atom may also be used as consisting of chlorine and bromine. charging stocks in this process. In some cases An object of this invention is to prepare (halo other aromatic compounds in which a nuclear alkyl) aromatic hydrocarbons. hydrogen atom is replaced by a halogen atom, a Another object of this invention is to prepare O hydroxyl group, or an amino group are also a phenyl haloalkane. utilizable as charging stocks. A further object of this invention is to prepare Dihaloalkanes useful in this process contain a phenyl chloroalkane. halogen atoms selected from the members of the A still further object of this invention is to group consisting of chlorine and bromine. These prepare an alkylphenylchloroalkane. dihaloalkanes also have one halogen atom at An additional object of this invention is to tached to a tertiary carbon atom (that is, a prepare 1-chloro-3-methyl-3-phenylbutane. carbon atom which is combined with three other One Specific embodiment of this invention re carbon atoms) and a second halogen atom at lates to a process for preparing an arylhalo tached to a non-tertiary carbon atom. Suitable alkane which comprises reacting an aromatic hy dihaloalkanes include 1,3-dichloro-3-methylbu drocarbon having a replaceable nuclear hydrogen tane, 1,3-dibromo-3-methylbutane, 1,2-dichloro atom with a dihaloalkane having one halogen 2 - methylpropane, 2,4-dichloro-4-methylpentane atom combined with a carbon atom that is bound and the like. chemically to three other carbon atoms in the Suitable catalysts for use in the process of this presence of a catalyst comprising essentially a invention comprise solutions of an aluminum Solution of an aluminum halide dissolved in a halide such as aluminum chloride, aluminum nitro hydrocarbon. bromide, or mixtures thereof, in a nitrohydro Another embodiment of this invention relates carbon such as a nitroparaffin or a nitroaromatic to a process for preparing an arylchloroalkane hydrocarbon. The nitroparaffins include nitro which comprises reacting an aromatic hydro 30 methane, nitroethane, nitropropanes, and nitro carbon having a replaceable nuclear hydrogen paraffins of higher molecular weights. Of the atom with a dichloroalkane having one chlorine nitroaromatic hydrocarbons, nitrobenzene is gen atom attached to a non-tertiary carbon atom in erally preferred as a solvent for aluminum chlo the presence of a catalyst comprising essentially ride and aluminum bromide. The different ni a Solution of aluminum chloride dissolved in a trohydrocarbons which may thus be used for nitroparaffin. 35 producing Solutions containing aluminum hal. I have found that certain dihaloalkanes in ides, and utilizable as catalysts in the present which a halogen atom is attached to a tertiary process, are not necessarily equivalent in that Carbon atOn and the other halogen atom is at Some nitro hydrocarbons are more suitable than tached to a non-tertiary carbon atom may be others for producing aluminum halide solutions, reacted with an alkylatable aromatic hydrocar 40 and particularly aluminum chloride solutions of bon in the presence of an aluminum chloride high catalytic activities. At about 20° C., the nitrohydrocarbon catalyst to form an aryl mono lower members of the nitroparaffin series in haloalkane. This is an unexpected result since cluding nitromethane, nitroethane, and nitro similar reactants in the presence of unmodified propanes, dissolve as much as an equal weight of aluminum chloride catalyst produced a diaryl 45 aluminum chloride to form a homogeneous liquid alkane and substantially all of the halogen con which may be contacted readily with hydrocar tent was eliminated as hydrogen halide. bons and dihaloalkanes in the process of this Aromatic hydrocarbons which may be used in invention. A nitroparaffin such as nitromethane this process include mono-nuclear and also poly 50 has a relatively high dissolving powder for alu nuclear hydrocarbons. The mono-nuclear hy minum chloride and forms with aluminum chlo drocarbons or benzenoid hydrocarbons comprise ride a Solution which is freely miscible with the benzene, toluene, xylenes, ethylbenzene, diethyl aromatic hydrocarbon as in the case of benzene, benzenes, propylbenzenes, and other alkyl ben and a nitroparaffin may thus be said to serve as . Zenes in which the alkyl group contains more a solutizer for dispersing aluminum chloride in 2,631,172 3 4. the aromatic hydrocarbon subjected to reaction. acting aromatic hydrocarbon and dihaloalkane. Thus if one part by weight of aluminum chloride Thus relatively high Speeds of Condensation are is dissolved in its own weight of nitromethane obtained with a given quantity of aluminum chlo and the solution is added to benzene, a clear, yell ride because substantially all of the aluminum low solution results with either 1 or 100 parts by 5 chloride thus introduced into the reaction mix weight of benzene, and accordingly, a homoge ture is available for catalyzing the reaction, a neous catalytic reaction may be carried out in condition radically different from that obtained the presence of such an aluminum chloride Solu when using Solid particles of aluminum chloride tion. Aluminum chloride So dissolved or dis when only the aluminum chloride on the Surface persed in a nitroparafin and an aromatic hydro 3 of the particles can be contacted with the react carbon may thus be brought into intimate con ing aromatic hydrocarbon and dihaloalkane. tact with a dihaloalkane so that one molecular The condensation of an aromatic hydrocarbon proportion of aluminum chloride can readily with a dihaloalkane to form a (haloalkyl) aro catalyze the reaction of as much as 250 molecular matic hydrocarbon is carried out preferably in proportions of aromatic hydrocarbon. ESSen the presence of a solution of aluminum chloride tially the same solutizing effect is observed when in a nitroparaffin and at a temperature of from any other order of mixing is used for the aro about -20 to about 100° C., and at a pressure matic hydrocarbon, aluminum chloride, and ni of from Substantially atmospheric to about 100 troparaffin. Thus while only about 0.2 part by atmospheres. The exact temperature employed weight of aluminum chloride dissolves in 100 ; in a given treatment depends upon the properties parts by weight of pure benzene, the presence of of the aroimatic hydrocarbons charged and the 0.6 part by weight of nitronethane in the benzene activity of the catalyst. Preferred reaction tem increases this solubility to about 3 parts by weight peratures include the range of from about -20 of aluminum chloride in 100 parts by weight of to about --50° C., in the presence of aluminum benzene. When three parts by Weight of alu chloride and aluminum bronide or mixtures minum chloride are shaken with 40 parts by thereof. Temperatures between 50° C. and weight of benzene, there is no visible evidence 00° C. are sometimes used but in general the of the formation of a solution, but after addi yield of (haloalkyl) arornatic hydrocarbon de tion of 0.25 part by weight of nitromethane, the creases at the higher temperatures, benzene layer becomes yellow. A further addi Ira effecting reaction between an aromatic hy tion of 0.35 part by weight of nitromethane causes drocarbon and a dihaloalkane according to the from 30 to 50% of the aluminum chloride to dis process of this invention, the exact method of solve, while after another addition of 1.1 parts procedure varies with the nature and proportions by weight of nitromethane, all of the originally of the reaction constituents. A simple procedure introduced aluminum chloride dissolves to give utilizable in the case of an aromatic hydrocar a pale yellow solution. Similarly, the addition of bon which is normally liquid (or if solid is readily one part by weight of 2-nitropropane to a mixture Soluble or dispersible in a nitroparaffin or other of three parts by weight of aluminum chloride Substantially inert liquid) and a dihaloalkane and 40 parts by weight of benzene, causes the consists in contacting the aromatic hydrocarbon solution of about one-half of the aluminum chlo and dihaloalkane with a solution of aluminum ride, while further addition of one part by weight chloride or aluminum bromide in a nitrohydro of 2-nitropropane causes all of the aluminum carbon, preferably a nitroparafin, using either chloride to dissolve and form a clear solution batch or continuous operation. Thus in batch of reddish, orange color. The particular nitro type treatment a solution of aluminum chloride paraffin chosen as a Solutizer for aluminum chlo in a nitroparaffin is charged to a reactor con ride is also dependent upon the nature and pro taining an aromatic hydrocarbon and the reac portions of the aromatic hydrocarbon and di tion mixture is then stirred or otherwise agitated haloalkane being reacted, the conditions of op while a, dihaloalkane is added thereto preferably eration and other factors. together with relatively small amounts of alu Solutions of the aluminum halide in the aro minum chloride to effect formation of a (halo matic hydrocarbon may be obtained not only by 50 alkyl) aromatic hydrocarbon. Only as much of use of liquid nitroparaffins and liquid nitroaro the aluminum chloride-nitroparafin solution is matic hydrocarbons, but even by use of crystalline added as is required for catalyzing the conden nitroaromatic hydrocarbons. The crystalline ni sation reaction at a desired rate, and the con tro-compounds, which may be considered to act densation may thus be catalyzed by the use of as solutizers for the aluminum halide in the a relatively Small quantity of aluminum chloride. aromatic hydrocarbon, include m-dinitrobenzene2 After the reaction, the product may be treated nitronaphthalenes, trinitrotoluene, etc. with a Small amount of water, sufficient to hy When aluminum chloride in the form of a solid drolyze the aluminum chloride and the result is used for catalyzing the condensation reaction ing mixture of reaction products is washed, dried, -of an aromatic hydrocarbon with a -dihaloalkane, 60 the principal reaction of the process is the forma and separated by fractional distillation. The de tion of a diarylalkane and the elimination of Sired (haloalkyl) aromatic hydrocarbon product substantially all of the halogen of the dihalo is then recovered and unconverted aromatic hy alkane in the form of a hydrogen halide. Also drocarbon and nitroparaffin are recycled to fur sludge-like material forms upon the surface of ther use in the process. the aluminum chloride catalyst during use and Cottinuous types of condensation treatment is thus lowers the catalytic activity of the aluminum carried out by introducing the dihaloalkane into chloride so that it is necessary to withdraw the a flowing stream of catalyst solution and nor sludge-like material and add fresh aluminum rially liquid aromatic hydrocarbon or normally chloride in order to proceed with the reaction. Solid arolinatic hydrocarboh dissolved in a suitable When condensing an aromatic hydrocarbon with Substantially non-reactive liquid solvent. The a dihaloalkane in the presence of aluminum chlo mixture of hydrocarbons, dihaloalkane and cata ride dissolved in a nitroparaffin, the catalvst is iyst contained therein and preferably some addi substantially in the form of a linuld mixture or tional hydrogen chloride is passed through a solution which is contacted readily with the rea baffled mixer, or other suitable reactor to effect

2,681,172 5 6 intermittent contact of the catalyst solution with tivity of the aluminum chloride by use of the the reactants. The conditions of tenperature nitronethane diluent thus gave a beneficial effect. and pressure einployed in a condensation treat Eacample III ment are Within the limits indicated above, but the particular conditions employed in ainy coil A solution of 140 grams of 1-3-dichloro-3- densation treatinent, vary with the molecular methylbutane in 240 grams of benzene was added weight and reactivity of the aromatic hydrocar during two hours to a stirred solution of 10 grams bon and the dihaloa ikane, the concentration and of aluminum chloride and 10 grams of nitro activity of the catalyst and other factors. It is methane in 24 grams of benzene, the tempera generally advantageous to dilute the dihaloalkane O tire being kept at 25-27 C. The mixture was with a portion of the aromatic hydrocarbon and stirred for an additional hour, then Washed, to introduce the resultant, inixture at a plurality dried, and distilled. There was obtained 99 of points throughout the reaction Zone rather gians (55% yield) of the 1-chloro-3-methyl-3- than to cominingle all of the dihaloalkane with phenylbutane, B. P. 93° at 3 mm., no 1.5195. the aromatic hydrocarbon prior to introduction 5 There was obtained 32 grains (22% yield) of a to the catalyst Zone. crystaline product, boiling at 171-173 at 2.5 mm. In the reaction mixture subiected to catalytic and neiting at 64-65°; analysis showed that this treatment, it is preferable to have present from product, was p-bis-(y-chloro-t-pentyl)-benzene about 1 to about 40 molecular proportions of aro formed by the further reaction of the 1-chloro matic hydrocarbons per one molecular proportion 20 3-methyl-3-phenyibutarie with 1,3-dichloro-3- of dihaloalkane. The reaction mixture obtained methylbutane, from such a continuous treatment is then reactised EacGimple IV with water or ammonia, to decompose the re The reaction of 50 grams of 1,3-dichloro-3- maining aluminum chloride and the liquid prod naethylbutane with 100 grams of t-pentylbenzene lict is then dried and distilled to separate uncon in the presence of 5 grams of aluminum chloride verted aromatic hydrocarbon (haloalkyl), aro dissolved in 3 gians of nitromethane was carried matic hydrocarbons, and nitrohydrocarbon Sol out, using a procedure similar to that described vent. The unconverted aromatic hydrocarbon in Example III and a reaction temperature of 2 and the recovered nitrohydrocarbon Solvent are C. There was obtained a 62% yield (56 grams) recycled to further use in the process. of 1-chloro-3-methyl-3-(p-t-pentylphenyl)bu The following examples are given to illustrate tane, B. P. 133-136° C. at 2 mm.; n.201.5085. the character of the result obtained by the use of claim as iny invention: the present process, although the data presented 1. A process for preparing an aryl chloroal are not introduced. With the intention of 'estrict kane which comprises reacting a benzene hydro ing unduly the broad scope of the invention. Carbon having a replaceable nuclear hydrogen Eacample I aton and 1,3-dichloro-3-methylbutane at a tem perature of from about -20° to about 50° C. in A Solution of 26 grams of 1,3-dichloro-3-meth the presence of aluminum chloride dissolved in ylbutane in 91 grams of benzene was stirred with a nitrohydrocarbon. 2 grams of aluminum chloride at 2° C. for eight A ) 2. The process of claim 1 further characterized hours. There was a very copious evolution of ii) that Said nitrohydrocarbon is a nitroparaffin. hydrogen chloride. The temperature Was then 3. A process for preparing 1-chloro-3-methyl allowed to rise to roorn temperature (without 3-phenylbutane which comprises reacting ben stirring) during eight hours, the upper layer was Zene and 1,3-dichloro-3-methylbutane at a tem separated from 9 grams of deep red catalyst perature of from about -20° to about 50° C. in sludge, washed, dried, and distilled. There was the presence of a catalyst comprising essentially obtained 9.5 grams (28% yield) of 1-chloro-3- a Solution of aluainum chloride dissolved in ni methyl-3-phenylbutane, B. P. 87-89° C. at 2 mm., tronethane. n20 1.5208 and 12 grams (29% yield) of a di LOUIS SCHMERLING. phenyl pentane, B. P. 129-131° C. at 2 mm., no 50 of 15619. Eacample II REFERENCES CETEED The following references are of record in the A solution of 4 grams of aluminum chloride in 6 file of this patent: grams of nitromethane was added to a solution 5 5 of 25 grams of 1,3-dichloro-3-methylbutane at UNITED STATES PATENTS 24° C. in 80 grams of benzene in an Erlenmeyer flask. A clear solution resulted; much hydrogen Number Name Date chloride was evolved after one minute, the tem 2,246,762 Schirm ------June 24, 1941. perature rising to 29° C. The flask was cooled to 2,308,419 Heitz et al. ------Jan. 12, 1943 20-21 C. and kept at this temperature overnight, 60 2,355,856 Dreisbach ------Aug. 15, 1944 The product was washed, dried and distilled. OTHER REFERENCES There Was obtained 14 grams (43% yield) of the i-chloro-3-methyl-3-phenylbutane, B. P. 81-82° Groggins, “Unit Processes in Organic Syn C. at 1.5 mm.; n.201.5195. Moderation of the ac thesis,' 3d edition, pp. 768-9 (1947).