INDUSTRIAL A N D ENGKNEERING CHEMISTRY
160%
Underkofler, L. A., Fulmer, E. I., Bantz, A . C., and Kooi, I?. I., Iowa State Coll., J. Sci., 18, 377 (1944) (95) Underkofler, L. A., Severson, GI M., and Goering, K, J., Iwn
(102) (103) (104)
Underkofler, L. A., Severson, G. M., Goering, K. 9.. and Christensen, L. M., Cereal Chem., 24, 1 (1947). (97) 'Vnger, E. D., Wilkie, H. F . , and Blankmeyer, XI, O., T'r(zm.4 m
(105)
(94)
a
ENC.CHEM.,38, 980 (1946).
(96)
Inst. Chem. Engrs., 40, 421 (1944). (98) von Loesecke, H. W., Chem. E%@. N e w s , 23, 1952 (1945). (99) Waksman, S. A., U.S. Patent 2,326,986 (Aug. 17, 1943). (100) Waksman, S.A , and Karow, E. O., IND. ENG.CHCN.,39, 82' (1947).
/109) Waksman, S. A., and Ksrow, E. O . , U. 8. Patent 2,394.03'' (Feb. 5, 1946).
RIEDEL and Crafts showed that, aluminurn chloride and other metal halides could be used as a condensing agent for alkylations, dealkylations, acylations, polymerizations, and her unit processes. Syntheses made possible through. the catalytic intervention of metal halides now include the preparat,ion of practically all classes of compounds. The more importanf of the syntheses include alkylation, acylation, halogenation, dehydration, dehydrogenation, isomerization, polymerization, and intra- and intermolecular rearrangements. The use of metal halides in syiithetic organic chemistry, like the employment of microorganisms (SO), is merely a convenient and important tool that can be used Cor the economic production of a wide varktjy of commercially useful compounds ( 8 , 14, bo). I n t'he foliowing review, however, the recent advances in alkylations, isomerizations, polymerizations, and Pries migrations that are catalyzed by Friedel-Crafts catalysts Rave not been included hecause of assignment to other contributors. MECHANISM OF REACTlON
The mechanisms of Friedcl-Crafts syntheses have long bcsrsubjects of experimentation and conjecture. K i t h the use of radioactive isotopes and new scientific tools, more light is beirig she(% on this phase of the reaction. Ulich ( S I ) has concluded that tht. ketone synthesis takes place eit,her as a homogeneous reaction after aluminum chloride has gone into joliitioni in the _Formof at! addition compound, or as a surface reaction if an excess of a h aninum chloride is present. The hydrocarbon synthesis k autocatalytie and proceeds rapidly after a heavy oil phase has been formed by the addition of aluminum chloride to the reaction products. The use of gallium chloride, which is readily soluble irr many solvents, makes possible hydrocarbon syntheses as a purely homogeneous reaction. Its eEcienxy, however, decreases during the reaction owing to poisoning of t,be alyst or disconlinuatior. of the promoter effect. I n 1937 Fairbrother (11) suggested that in Friedel-Crafts reactions involving acyl and alkyl halides, the addition complexez bhat are formed may be regarded as coordination compounds containing the anion (AlC14)-: CH&OCl
+ MCI, --+ ;(:.HsCOj
-+
4 (AICh)
In the anion all the chlorine atonia concerned in the reactiorj ehould have an equal chance of escaping as hydrogen chloride,
Vol. 40, No. 9
Wallerstein, L ~INO. ? Ewc;. C H E M 31, ~ , 1218 (1939). Walton, M . T., U. S. Patent 2,368,074 (Jan. 23,1946). Ward, G. E., Lock\wood, 1;. B., Tabonkin, B., Stubbs, 9. J,, and Roe,E. T., Can. Patent 416,593 (Nov. 23, 1943). Ward, 6. E., Pettijohn, 0. G , , and Cophill, R.D., ISD. EN@. CHEM.,37, 1189 (1945).
(106) Wickerbam, L. J., et al., Arch, Bbchem., 9 , 95 (1946). (107) Wileyp-4. J., Johnson. M. J., M c C o y , E., and Pe IND. ENO.GIEM., 33, 606 (1941). (108) Williams+A. E., Mfg. Chemist, 16, 239 (1945). Arch. Bio(109) Wood, R.G., Brown, R.V;'~~m d Werkman, C~ chem., 6 , 213 (1945), IVR:D
July 6, 4948.
T h i a wab confirmed eP;perirrrenically b y the w e of radioactive chlorine isotopes. Korshak and Kolesnikov (18) have addured further evidence in support of Fairbrother's hypothesis. I\ her. benzenp, ethyl chloroformate, and aluminum bromide ere permitted to ieact under agitation, the evolved gases icjnraineu 132 26 mole yo hydrogen bromide and 17.74 mole 7, hydroger, chloride. Ailurninurnbromide and acetyl chloride yield a cornplex which, when sublecied t o distillation, yields a mixture of ace:) 1 chloride (83.6Sc6) and acetyl bromide (16.32%). Tha rpaetxon of the above complex with absolute ethanol or beneenr gave analogously mixturrs of hydrogen bromide and hydrogrlrr vhloride in similar ratio. Irl furthev studies, Korshak and Koleiriikov (19: ahowred that che rraLtion of aluminum bromide with diverse albjl, aryl, and ari lalli-j1 chlorides resulted in the forniation of about 75% hydrogen bromide and 25% hydrogrn chloiide Similarly t h e use of aluniinuni chloride with bromo compounds gave approximately 7 5 c hydrogen chloride and 25m0 hydrogen bromide These resulk confirm the belief that. the mechanisrr, depends on the formation of a complex containing the ion (AlX,)rhat can react with equal fnrilltv through any of the halopri *,omt.
XHEWMODYNAMlCS
OF FRIEDELCRAFTS REACTIONS
'1he heals of formation of APC13 aluminum chloride comploxcs wth orgacic compounds are ir? eome inqtances large, and thi4 complex formation has a great effect on the courw as svpll x4 products of reaction.
In reactions such as shown below,
n:k~feCX(g)f CsHs(l)
A4.1CY*
--+
CGR6_.,Me,(l)
+ nRC1
(2:
Campbell and Elejr (9) found that the heat of formation of h!Brs(C&&CHO), is 30 kg.-cal. per mole of aluminum bromide. This compiex formation, by making total free energy of reactlion strongly negative, is fmport,ant in obt,aining the excellent no~-rnd yields. In Reaction 2 thermodynamic calculations, excluding complex formation, show no preference among toluene, CsH4(CH,),, and @e113(CH3)3. The heats of complex formation are hICla.@&L(CHa)z= 22 kg.-cal.; AIC13.CflHa(CHs)a= 8 kg.-cal.; and AICI3.GHbCH,= 0 kg.-oxl.
September 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
FRIEDEL-CRAFTS CATALYSTS The technical and particularly the patent literature of the past
8 years reveals intensive activity in exploring the properties and uses of diverse Friedel-Crafts catalysts. T o students of the Friedel-Crafts reaction, many of the patents are based on doubtful novelty. I n general, the patents can be classified into four groups: fluidization processes, preparation, modification, and removal. Fife (12) claims a highly active liquid catalyst prepared by fusing aluminum chloride and a molar excess of antimony trichloride and treating the resultant mixture with hydrogen chloride until at substantial amount of the aluminum chloride has been converted to a complex double compound with hydrogen chloride. Arnol ( I ) indicates that the activity of a Friedel-Crafts catalyst deposited on a porous carrier is increased by heating the carrier in the presence of oxidizing gas at 450" to 800" C. until multivalent compounds are oxidized to the highest state. Another patent (24) suggests that organoaluminum compounds-such as Me9Al,Cls, derived from reaction of methyl chloride with finely divided aluminum chIoride-be charged into the system containing hydrocarbons. Dry hydrogen chloride is then introduced into the reaction zone and aluminum chloride is thus generated in situ. Schmerling and Ipatieff (%9)claim a modified Friedel-Crafts catalyst useful for various organic condensation reactions, isomerization, and polymerization reactions. Equimolecular proportions of ahminum chloride and sulfuric acid are interacted at temperatures up to 120" C., forming a compound of the type HS04.AlC12. This modified catalyst is relatively less active more selective, and less hygroscopic than aluminum chloride. For some years it has been known that aluminum chloride forms relatively stable insoluble complexes with certain compounds such as alkalene oxides, pyridine, ammonia, and amines. These agents can thus advantageously be employed in conjunction with catalytic Friedel-Crafts reactions for the removal of the catalyst from reaction products. This principle is recognized by Johnson and Wilson (16),who suggest the addition of 0.2 to 2.0% by weight of a slightly oil-soluble amine for the removal of nonsettling Friedel-Crafts sludge from treated oils. Amyl, hexyl, and cyclohexyl amines and particularly tetraethylenepentamine are useful. The mixture is heated to about 90" C. and the precipitated complex is removed by filtration through suitable clays. Robinson ($7) claims achievement of the same object by passing dry ammonia into the reaction mixture in an amount to deactivate the catalyst complex without neutrdizing the hydrogen halide that is present. Latchum claim th?t liquid orthophosphoric acid, containing from 50 to 85% of &PO4 @ I ) , or concentrated sulfuric acid (22),may also be used to scrub out residual aluminum chloride from hydrocarbon vapors containing hydrogen chloride and aluminum chloride. The aluminum chloride reacts with phosphoric or sulfuric acid to form hydrogen chloride which appears in the scrubbed effluent.
ACYLATIONS
Ketones and Keto Acids. A systematic study of the FriedelCrafts acetophenone synthesis has been made by Salini and Vaihkonen (28). The effect of such factors as temperature and time of reaction, ratio of reactants, and solvent on the formation of acetophenone from benzene and AcCl, AcOH, or AcgO was investigated. A series of control runs was made for a given variant with different reaction times in order to obtain the maximum yield. Under proper conditions, approximately equivalent yields of acetophenone are obtained by using acetyl chloride, acetic acid, or acetic anhydride as acylating agent (14). The use of an excess benzene was more effective as a fluidizing agent than either petroleum ether or carbon disulfide in producing higher yields of ketone.
1609
The present emphasis on the production and utilization of pure chemicals from petroleum has encouraged the exploration of acylation reactions in the presence of Friedel-Crafts catalysts Byrns (7) has reported that 25% yields of ketone can be obtained by treating diisobutylene with acetic anhydride in the presence of zinc chloride, the principal ketone being 2,2,4-trimethvlpentane-4-methyl ketone. The acylation of o-nitrophenol with acetyl chloride in the presence of aluminum chloride yields about equal parts of 4,3-HO(0zN)C6H30CCH~ and unchanged onitrophenol (4). The acylation of methyl r-resorcylate with acetic anhydride has been studied by Desai and co-workers (IO), who used aluminum chloride as catalyst and nitrobenzene as solvent. Methyl-2,6-dihydroxy-3 acetyl benzoate was obtained as the reaction product.
OH
~2>-cooca, O=c ow E'uson and co-workers (IS) have prepared o-diaroylbenzenes
ar d 1,%diaroylcyclohexanes by condensing phthaloyl chloride and trans-hexahydrophthaloyl chlorides, respectively, with mesitylene. Using aluminum chloride as catalyst and carbon disulfide as solvent, these investigators obtained the diketones as reaction products and concluded that phthalide formation in Friedel-Crafts reactions of phthaloyl chlorides may be prevented by the introduction of a mesitoyl group. The influence of hydrogen bromide salts on yields of diacetyb carbazole prepared by the Friedel-Crafts reaction has been studied by Beilin ( 2 ) . Yields of 80 to 84% of l,%diacetylcarbazole are obtained from 9-acetylcarbazole with au-tyl chloride and aluminum chloride, provided that 0.06 to 0.1 molar amount of calcium bromide or magnesium bromide is present, in the mixture. The beneficial action of bromides is greater when commercial rather than sublimed aluminum chloride is used. The efficacy of the added bromides is attributed to a double decomposition with acyl chloride, which results in the formation of the more reactive acyl bromide. The condensation of 3,6-dimethylphthalic anhydride with benzene apparently does not proceed as rapidly as the corresponding reaction of phthalic anhydride and xylene. When 3,6-dimethylphthalic anhydride is refluxed with benzene and aluminurn chloridg for 5 hours, only 12% of 2-benzoyl-3,6-dimethylbenzoic acid is obtained (26). Heating in tetrachloroethane for 8 hours a t 100" C. gives a 57% yield, the unreacted material being recovered unchanged. Good yields of 4-haloacetonaphthones were obtained by Jacobs and co-workers (15) by treating a-chloronaphthalene with acetyl chloride in the presence of aluminum chloride, using carbon disulfide as a solvent. A yield of 89 t o 91% of crude 4-chloro-1-acetonaphthonewas obtained.
MISCELLANEOUS REACTIONS Buu-HOT and Janicaud (6)have extended the earlier work of Kane and Lowy (17) in condensing esters of carboxylic acids with aromatic compounds. The reaction of ethyl chloroformate with benzene leads to ethylation rather than acylation, and ethylbenzene is obtained as the principal product. The Friedel-Crafts reaction is used for the preparation of a mixture containing a phosphine halide that can be used for the modification of rubber (23). Toluene, pho'sphorus trichloride, and aluminum chloride are condensed a t the reflux temperature and the mixture is cooled to permit, separation into two layers
INDUSTRIAL AND ENGINEERING CHEMISTRY
1610
The lower lager is used to treat rubber, and a product curable with zinc oxide, sulfur, and an aceelerato1 is obtained. Oxidative ring closure (Scholl reaction) induced by FriedelCrafts catalysts has been studied by Buckley (6’1. Aluminum chloride was used to effect the condensation and subsequent dehydrogenating ryclization of naphthoyl and aroyl chlorides. 2-Naphthoyl chloride ti eated M it h l-m~.thS’lnaplithalene in carbon disulfide and relativelj small amounts of aluminurn chloride gives 4075 4-mcthgl-l,2’-dinaplithyl ketone. The same reactants in the presence of larger amounts of aluminum chloSimilar ride yield 4-methy1-9,10’-benzoni~~obenzanthrone. condensations were made with l-mcth?;lrinphthalerie and 01her naphthoyl arid aroyl chlorides
INDUSTRIAL O P E R A T I O N S A by-product of the rccent costly war is the informat’ion pertaining t o some commercial operations carried out either in government plants in the United States or in numerous plants in Germany. The domestic Friedel-Crafts data relate largely to alkylation, isomerization, and polymerization processes associated a i t h the production of synthetic rubbers and aviation fuel. Similar and additional information is cont’ained in reports prepared for the several “Intelligence” agencies. The preparation of 4’-ethyl-2-benzoylbenzoic acid and 2cthylanthraquinone, as carried out by I. G. Farbenindustrie at Ludwigshafen, is descriiied by Robell ( d G ) , who discusses the chemical basis of the process and describes the plant facilit,ies. Flow sheets of the operations and operating yields are included. Chlorobenzene, which is not as reactive as ethylbenzene, is employed as a solvent to fluidize t,he reactants. Anhydrous chlorobenzene and ethylbenzene are pumped to the reactor and phthalic anhydride is then introduced. Aluminum chloride is added and the gases consist,ing mainly of hydrogen chloride and traces of phosgene are conducted to porcelain Tvash tower8 by means of a fan. The condensation is started a t room temperature, and after all the reactants are introduced t.he charge is heated for 1 hour a t 35 t o 40 O C. The condensation mass is decomposed with 10% wlfuric acid, The charge at 85’ t o 9O0 C. flaws to a separator where the aluminum chloride solution is withdrawn from the bottom of.the vessel while the keto acid in solution in chlorobenzene remains. After the ethylbenzoylbenzoic acid is washed free o f aluminum chloride, it is sent to an extractor where it is treated with a 2.7% solution of sodium hydroxide at 80 C . The effluent, from the extractor goes to a decanter in which the chlorobenzene is withdrawn at the base. The aqueous solution of the sodium 3alt of the keto acid is freed of traces of chlorobenzene by means of a suction pump, and ethylbeneoylbenzoic acid is precipitated by t,he addition of 10% sulfuric acid. The keto acid is then filtered and washed. For t,he production of 100 kg. of 4’-ethyl-2-benzoylhenzoic acid the following utilities are required: Electricity Cooling water
42 kw.-hr. 240 cu.m.
Steam Operating labor
Vol. 40, No. 9
L I T E R A T U R E CITED Alniol, C o n ~ a dBritish , Patent 570,167 (June 25, 1945). Beilin, A . A,, J . Gen. Chcm. ( U . S . S . R . ) ,14,109G-10G (1944). Braiidner, J. D., and Goepp, 1%.M.,Jr., F I A T 1311. Brown, F. C . , J . Am. Clzem.. SOL,68, 872-3 (1946). Buckley, Gerard, D., S. Ch,rm. Soc., 1945,561-4. Buu-Hol and Janicaild. Joseph, Bull. soc. chim., 12, (;40--2 ( I 945). B y m a , A . C . , U. 8 . Pateiit. 3,355:703 (;Lug. 16, 1944). Callowsy, N. O., Chem. Rec., 17, 327 (1935). Campbell, T I . , and Eley. D. D., Deuai, R . D., Radha, K . d., and S C ~23A, ., 305-6 (1046). Fairbrother, F., J . Chem. Soc., 1937,503. Fife, J. G., British Patent 583,976 (June 11, 1943). Fuson, R. C., Speck, S.B., and Hatchard, W. R., J . D r g . C‘hem., 10, 56-61 (1945). Groggins, P. H., “‘Unit Processes in Organic Syntheuk,” Chap. X I I , New York, McGraw-Hill Book Co., 1947. R.alls, J. W., and Robson, ,T. J . . Jacobs, T. L., Winstein, 8. W., J. 0 ~ g C. h r m . , 11, 27-33 (1946). Johnson, F. Id., arid Wil,ion, N. B . , U. S. Patent 2,368,59n ( ~ S J I . 30, 1945). Kane,T., and Lows, A., J . A m . Chem. Soc.. 58, 2605 (lY3C). Xorshak, V. V., and Kolrsnikov, G . S., J. Gen. Chem. (U.S.S.R.), 14,435-7 11944). I b i d . , pp. 1092-5. JZranzlein. G., “Alurnirmrii Ciil orid in del organischeri Cht~niie,” Berlin, V Martin, G. D., I b i d Mavit,y, J. AI., Xewman, M. S . (1944). Robell, John, FIAT K e p t . 917, U. 8.Dept. Commerce ( A u ~ i i s t 1946). Robinson, 1%..\., U. 8 . Pawill 2,376,088 (May 15, 1945). Salmi, E.J., and \-a,ihkonen. Ensio, Suomen Kemistilehti, 19B. 132-8 (1946). Schmerling, Louis, and Ipat,icff, VlRdimer, U. S.Pat,ent 2,:369,691 (Feb. 20,1945). Silcox and Lee, IND. I ~ G(:HEM., . 40, 1610 (1948). IJlinh, H., Oel u . Kohlc in Ckniejnschaft niit BrennstoLT-C‘C’henl., 39,523-7 (1943). RECEIVED May 2 2 , 1948.
2.7 tons 11man-hr.
The Friedel-Crafts preparation of p-phenylethyl alcohol as practiced by I. G. Farbenindustrie a t Ludwigshafen has been reported by Rrandner and Goepp (3). The operations follow e familiar pattern with the exception that a nitrogen atmosphere is used during the condensation. The reaction is carried out in a n iron vessel provided with a jacket for brine circulation, a n agitator and the customary other connections and instruments. The condensation of ethylene oxide and benzene in the presence of aluminum chloride is carried out a t 5 t o 6 O C. Higher temperatures appear to favor the formation of dibenzyl; lower temperatures are not feasible because of freezing of benzene. The reaction product is hydrolyzed in a n agitated, lead-lined, steel vessel and allowed t o stratify. The upper benzene solution of crude phenylethyl alcohol is partially purificd by distillation at 15 mm. absolute to give a 90% product. Final purification is effected by forming a crystalline addition compound with calcium chloride, which is filtered and then washed with benzene. The complex is decomposed by dissolving in warm water, and the phenylethyl alcohol layer is removed and distilled.
Chlorination Equipment st Hooker Electrochemical Company
