INDUSTRIAL AND ENGINEERING CHEMISTRY
2012
(400) Tsuchiya, H. M.,Koepsell. H. J., Corman, J., Bryant. G., and Jackson, R. W., Bact. Proc., 22 (1952). (401) Tsuchiya, M., J . Chem. SOC.J a p a n , 20,587 (1944). (402) Umesawa, H., Hayono, S., Ogata, Y., and Okami, Y., J . A n t i biotics (Japan), ( S u p p l . B ) , 3, 1 (1950). (403) Umesawa, H.,and Maeda, K., J . Antibiotics (Japan),2, 41 (1 950). (404) Umesawa, H., Osato, T., Utahara, R., Yagashita, K., and Okami, Y., J . Antibiotics (Japan),( S u p p l . B ) ,3, 16 (1950). (405) Van Dyok, P., and DeSomer, P., Antibiotics and Clkemotherap?~, 2,184 (1952). (406) Vergnaud, P., U.S. Patent 2,541,581(Feb. 13,1951). (407) Verona, O.,“The Microbiology of Fermentations and Indus-
trial hlicrobiology,” Pirense, Casa ed. Dr. Luiji Maori, 1950. (408) Vitucci, J. C., Bohonos, IS., Wieland, 0. P., Lefemine, D. V., and Hutchings, B. I,., Arc?k. Biochem. Biophys., 34, 409 (1951). (409) Vohs, R.L.,Maddock, I€. M., Catron, D. V., and Culbertson, C . C., J . A n i m a l Sci., 10,42 (1951). (410) Voss, J. G.,U. S. Patent 2,567,257(Sept. 11, 1951). (411) Wakaki, S.,J . Antibiotics (Ja.pan),4, 479 (1951). (412) Ibicl., p. 545. (413) Waksman, S. A,, Antibiotics and Chemotherapy, 1, 1 (1951). (414) Waksman, S.A.,J . Hist. Med. Allied Sci., 6, 318 (1951). (415) Walker, T. K.,Hall, A. N., and Hopton, J. W., Nature, 168, 1042 (1951). (416) Wallace, H.D., Ney, W. A, and Cunha, T. J., Proc. SOC.Esptl. B i d . Med., 78,807 (1951). (417) Wallace, T., “Trace Elements in Plant Physiology,” Chroriica Botanica Co., 1950. (418) Wall St. J. (April 29,1952). (419) Walton, R. B., Antibiotics aikd Chemotherapy, 1, 518 (1951). (420) Weindling, R.,and Kapros, C., Bact. Proc. 48 (1951). (421) Weirich, L.,U. S. Dept. Commerce Chemicals Division, personal communication (1952). (422) Westerdyk, J., Antonio van L,eeuwenhoek. J . M i c r o b i d . S e d . 12,223 (1947). (423) Westhuisen, G. C. A . vander, Spruit, J. P., and Sephton, H. H.,J . Applied Cheni. (Londoa),1, 356 (1951).
Vol. 44, No. 9
(424) Wholan, W. J., and Naer, H., B m h e m . J . , 48,416 (1951). (425) White, J., Wallerstein Labs. Comnmuns., 14, 199 (1951). (426) White, J.,and Munns, D. J., ,J. I n s t . Brewing, 56,141 (1950). (427) Ibid., p. 194. (428)Whiteside-Carlson. V., and Carlson, W. W.,Science, 115, 43 (1952). (429) Whiteside-Carlson, V., uud Itosano, C. L., J . Bact., 62, 583 (1951). (430) Wijmenga, H.G.,Veer, W.L. C., and Lens, J., Biocham. et Biophys. Acta, 6,239 (1950). (431) Wiley, A. J., Holdenby, J. &I., Hughes, L. P., and Inskeep, G. C . , I N D . E N G . C H E 1702 ~,~~ (1951). , (432) \liilson, J. E.,Nature, 169,715 (1952). (433) Wolf, D. E., Valiant, J., and Folkers, K. A., J . Am. Chem. Soc., 73,4142 (1951). (434) Wood, T.R.,and Hendlin, D., U. S. Patent 2,595,499(May 6, 1952). (435) Woodbine, M.,Gregory, hl. E., and Walker, T. K., J . Ezptl. Botany, 2,204 (1951). (436) Woodruff, H. B., U. S . Patent 2,685,713(Feb. 12, 1952). (437) Wright, L. D., Cresson, E. L., Skeggs, €I. R., Peck, R. L., Wolf, D. E., Wood, T. R.. Valiant, d., and Folkers, K. A., Science, 114,635 (1951). (438) Wright, L.D., Skeggs, H . H..and Cresson, E. L., J . Am. Chem. Soc., 73,4144 (1951). (439) Yagishita, K.,and Umeeawa, H., J . Antzbiotics ( J a p a n ) , ( S u p p l . B ) , 3,lO (1950). (440) Yasuda, H., Enomoto, K., and Skamoto, A., J . Antibiotics ( J a p a n ) ,4,493(1951). (441)Yasuda, H., Hori, H., Yamazaki, K., and Misoguchi, S., I b i d . , 4,433 (1951). (442) Yasuda, H., Yamasaki, K., and Misoguchi, S., Ibid., 4, 618 (1951). (443) Yasuda, S., Enomoto, K., Yamasaki, K., and hlisoguchi, S., Ibid., 4, 173 (1951). (444) Yonehara, H., Toyoma, T., and Sumiki, Y., Ibid., 4, 16 (1951). (445) Yuill, J. L.,Biochem. J., 49,xix (1951). (446) Zief, M., and Stevens, J. R., J. Am. Chem. SOC.,74,2126 (1952). REOEIVED for review J d Y 7,1952. ACCEPTED July 9,1952.
Friedel-Crafts Reactions .
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NATIONAL PRODUCTION AUTHORITY, WASHINGTON, D. C.
SAMUEL B. DETWILER, Jr., BUREAU OF AGRICULTURAL AND INDUSTRIAL CHEMISTRY, U. S. DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C.
Friedel-Crafts reactions continue to hold the interest of many investigators and familiar names appear in the current literature on the subject. In contrast to previous years, there i s a dearth of contributions from the petroleum industry to the patent and technical literature on FriedelCrafts catalyst and mechanism of reaction. Current research, which is largely of a fundamental character, confirms accepted concepts regarding the formation of ionized complexes and halogen exchange between the catalyst and organic reactants.
T
HE Friedel-Crafts reaction continues to be an interesting
and fruitful field for research and development. Last year, the reports in this annual review emphasized theory of reaction, thermodynamics, and the preparation of chlorohydrocarbons. I n this review, new developments relate to the exchange of chlorine from solid aluminum chloride, and further confirmation is obtained t h a t the Friedel-Crafts reaction is an electrophyllic transformation in which the role of the catalyst (aluminum chloride, ferric chloride, or sulfuric acid) is limited to the production Of the cation, Xf, in the general reaction:
ATH
+ X + e ATX + H +
where Ar is a n aromatic group and X + is a cation such as D+, CHa+, or CH&O+. The current literature shows a marked reduction in the number of patents pertaining to the Friedel-Crafts reaction and catalysts therefor. Instead, there are a number of papers of Russian origin dealing with Radzivanovskiy aluminum chloride prepared from aluminum chips and hydrogen chloride.
MECHANISM OF REACTION Reactions of alld exchange of hydrocarbons in the presence of acid catalysts appear as particular caSeS of the Friedel-Crafts reaction, Chiurdoglu and Fierens that it is permissible to attribute such chemical transformations to the mechanism bJr Fairbrother for alkylations (11) and acylstions (12) which is exemplified by reactions of benzene:
CeH6 f A + S PhA
+ H+
September 1952
INDUST'RIAL A N D E N G I N E E R I N G C H E M I S T R Y
where A is a cation such as D+, Me +,Ac +,etc. Monomethylation of toluene to xylenes, considered as a type of Friedel-Crafts synthesis, comprises two important steps-a rapid monomethylation of toluene which, kinetically, depends on the speeds of formation of the isomeric xylenes, and a slower isomerization tending to realize a thermodynamic equilibrium between the reaction products. The relative abundance of derivatives formed in the c o m e of a particular Friedel-Crafts reaction is a function of factors inherent in experimental conditions, The electronic theory and the use of molecular diagrams satisfactorily account for ortho-para orientation in the rapid momomethylation stage (step 1). Thermodynamic data are in good agreement with the direct experimental study of isomerization and hydrocarbon exchange a t equilibrium (step 2). Further confirmation of halogen migration in Friedel-Crafts reactions has been adduced by Wallace and Willard (28). These investigators have shown that the chlorine in radioactive aluminum chloride exchanges readily with that in liquid carbon tetrachloride. The exchange with carbon tetrachloride and chloroform occurs rapidly even a t the melting points of the compounds (-21" and -63O C., respectively) if the aluminum chloride has not been exposed to moisture. Partial hydroxylation of aluminum chloride to AIC120H inhibits the exchange a t low temperatures and decreases the rate at higher temperatures. Except at higher temperatures, exchange is incomplete. Whereas complete exchange occurs a t 100" C. in 2 hours a t ratios of aluminum chloride to carbon tetrachloride greater than moles per liter, relatively little or no exchange occurs a t lower ratios. This observation suggests that exchange can occur only when an aluminum chloride surface is present. Mixtures of gaseous aluminum chloride and carbon tetrachloride can be maintained a t 140" C. for 9 hours with no exchange. Wallace and Willard believe that the above-noted characteristics of the exchange between aluminum chloride and carbon tetrachloride cannot be explained by the carbonium-ion type of mechanism commonly used to rationalize Friedel-Crafts reactions. Butyl chloride and amyl chloride, as is well known, exchange chlorine easily with aluminum chloride and this exchange appears to be a convenient general method for tagging organic chlorides with C18*. In subsequent investigations ( I ) , it was shown that under proper conditions, exchange of chlorine occurs readily between ,solid aluminum chloride and gaseous carbon tetrachloride, chloroform, propyl chloride, and benzyl chloride a t room temperature with a contact time of a few minutes. A yellow or brownish color was imparted on the aluminum chloride, and in each case hydrochloric acid was found in the products of reaction. Gaseous carbon tetrachloride and benzene were found to undergo a FriedelCrafts type reaction on an aluminum chloride surface, which is in accord with the earlier observation that an aluminum chloride surface is necessary for chlorine exchange between liquid carbon tetrachloride and aluminum chloride. Brown and roworkers ( 3 )find that, contrary to the conclusions of Van Dyke (27), there is evidence of 1:l addition compounds of Friedel-Crafts catalysts with alkyl halides. If a molecular weight determination of gallium chloride in methyl chloride is made, the figures indicate that 1 mole of solvent is effectively removed to form CHsC1-GaCla in solution. When the excess of methyl chloride is removed, two vapor pressure plateaus are observed, the first corresponding to a saturated solution of the addition complex CHaCl-GaCla in methyl chloride, the second to the dissociation of the solid addition compound. According to these investigators, hydrogen chloride and aluminum chloride or gallium chloride do not combine between -120' and +300° C. Aluminum chloride and toluene do not react a t -80" C., but in the presence of hydrogen chloride a soluble compound of toluene and HAIClr or HGaC14 is formed. The kinship in the mechanism of halogenation and FriedelCrafts yeactions was demonstrated by conductivity studies with
2013
organic reaction mixtures. Murakami and Yukawa (16) found that when an equivalent amount of anisole is added to a solution of bromine in various solvents (0.0073 mole per liter), the specific conductivity of the reaction mixture rose abruptly to a maximum and then gradually decreased. The observed phenomena are explained by postulating an ionized intermediate complex (HBrC.CH:CH.C( :OMe).CH: CH)+Brprior to the formation of the substitution product, BrC&140CHs, and hydrobromic acid. The specific conductivities obtained by adding anisole to a bromine solution in various solvents is as follows:
Solvent
cc14 cs2
AoOH 99% AcOH 90% AcOH AczO PhH
Spec.
Conductivity
