Friedel-Crofts Reactions -__
HAROLD T. LACEY, RESEARCH
DIVISION,
AMERICAN CYANAMID CO., BOUND BROOK, N. J .
During the past two years, Friedel-Crafts reactions have been a fertile field for research and have also produced notable commercial applications in the dyestuffs, intermediates, and polymer industries. Current research of a fundamental character has added to our knowledge of the mechanism of reaction and the function of intermediate complexes, particularly as applied to isomerization, disproportionation, and alkylation.
T
HE numerous and varied applications of the Friedel-Crafts
reactions, appearing in the literature in the past two years, continue to emphasize the usefulness of this reaction. The last report in this Annual Review by Groggins and Detwiler emphasized the mechanisms of reaction, catalysts, acylations, and miscellaneous Friedel-Crafts reactions. I n the interim, notable progress has been made in clarification Me of the various theories concerning the mechanism of the Friedel-Crafts reaction particularly as applied to isomerization, disproportionation, and alkylation of aromatic hydrocarbons. I n this Unit Process Review an attempt is being made to shift the emphasis to practical process improvements. Some of the adwnces in the knowledge of the theory and mechanism of the reactions have also been stressed because this knowledge is the foundation of the practical improvements and points out the reasons for the reaction conditions necessary to achieve the desired results. I n a biennial review of this type, it is difficult to give proper emphasis to the importance of these contributions without reviewing the literature of the prior art. Several excellent theoretical review articles of the Friedel-Crafts reaction have been published (WS, 28, 44). The paper by Brown and coworkers (IS) on reaction of alkyl halides with aromatic nuclei is particularly noteworthy since it contains important data hitherto unpublished. These authors point out that the mechanism of any phase of the Friedel-Crafts reaction may vary depending upon the number of interdependent variables such as the nature and relative amounts of reactants, catalysts, and solvents as well as temperature and pressure. Also associated with these primary variables are the products of the reaction, which may either be concentrated during the reaction or removed from the sphere of the reaction, depending on the experimental conditions.
groups in the isomerization niechanism does not involve the formation of a carbonium ion in the alkyl halide. For example, under the proper conditions for isomerization, with either HAIBra or HBFl catalysts, n-propyl derivatives fail to give any isopropyl compound. These changes are therefore Intramolecular, involving migration of the alkyl group, closely related to the hydrogen exchange reaction (4, 61) and in the case of the xylenes may be represented as
H Me
Me
€€
Me
Me
1
I n general, in the polyalkylbenzene series, the following rule holds-the more acidic the nature of the ternary complex the greater is the tendency to form the most basic isomer. This rule is applicable to either isomerization, disproportionation, or alkylation. Condon (36) has determined the relative basicities (essentially, relative equilibrium constants for reaction with €IF,BFI) of a series of methylbenzenes (60), based upon m-xylene as 1. The higher homologs tend to be more basic. The meta-isomers are the most basic of the dialkylbenzene hydrocarbons, the symmetrical form is much the most basir of the trialkyl-isomers and the related tetranlkyl-isomer (1,2,3,5) is considerably more basic than the other two tetraalkyl-isomer.. The results obtained are Exptl. Benzene Methylbenzene (toluene) 14-Dirnethylbenaene p xylene) 1:2-D!methylbenzene [o-xylene) 1,3-D1methylbensene (m-xylene) 1,2,4-Trimethylbenzene (psuedocurnene) 1,2.3-Trimethylbenzene (hemimellitene) 1,2,4,5-Tetramethylbennene (durene) 1,2,3,4-Tetramethylbenaene(prehnitene) 1,3,5-Trirnethylbensene (mesitylene) 1,2,3,5-Tetramethylbenaene (isodurene) Pentamethylbenzene Hexamethylbenzene (mellitene)
ISOMERIZATION AND DISPROPORTIONATION Since Friedel-Crafts alkylation reactions are reversible, i t follos E that all types of Friedel-Crafts reactions with alkylated aromatic hydrocarbons are often accompanied by isomerization and disproportionation. Considerable light has been thrown on the conditions causing isomerization and disproportionation during thebe past two years, and the resulting knowledge of these rearrangements has led to a better understanding of other Friedel-Crafts reactions. For the most part, this work on isomerization and disproportionation has been carried out with the use of unstable acids such as HAlCL, HBlBrd, and HBFI (4, 61). These acid catalysts do not exist as such in the free state (21, ZT), but ternary complexes of them with aromatic hydrocarbons have been prepared and their effects on the isomerization equilibria have been determined. Several investigators (4, 69, 61) have demonstrated that the migration of alkyl
H
(CE.
'd.'ool)
Calcd. 0.0002
0.05 0.10
1
2
2 6.7 9.4
156 311 484 4933
I n line with the general rule, there has been a considerable advance in our knowledge of the ternary complexes. For example, in the presence of exceBs hydrogen bromide a t room temperature Baddeley and coworkers ( 4 ) have isolated for the first time ternary complexes of the type (ArH), (.41Bra,HBr),. I n the case of the xylene, where the HBr was added to a fixed ratio of AlBra/xylene, a practically colorless crystalline complex, (m-xylene) (AlBrZHBr)p, (m.p. 52' to 54' C.), as well as a dark oil, (xylene)s (iZlBraHBr), containing 66% m-isomer, were obtained from either o-xylene, m-xylene, or p-xylene illustrating isomerization to m-xylene as the HBr content was increased. These ternary complexes were stable only in an atmosphere of HBr and readily lost half of this component a t higher temperatures or when subjected to a stream of dry nitrogen, forming dark 1827
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1628
browii oil8 of composition (ArH), A1213rb.HBr, corresponding to those obtained previously by ot.lier investigators. This lattor complex would also normally be present in a Friedel-Crafts alkylation reaction using alkyl bromide and A l I h , inasmucli 11s the HBr would be a product; of the reaction. I n the case of benzene \vhich less reactive iii t h e FricddCrafB reaction than its homologs, ley and King ( 4 0 ) have foruitl that whereas AIZBrGf o r m an ideal solution in benzene, thrJria ix no interaction between HBr and A1Br3 in the absence of beiizerit:. The ternary system HBr-&Brs-Ce.H6 shows a profound intwaction of its components. Two liquid phases are formed in thermodynamic equilibrium wit81isolid AI2Brs(if present) and ga,seouu HBr, the upper liquid phase (AltRr5-bensenc: solution) being weakly ionized and the lover "red oil" phase (AlnB1.6-I€Wr-6CeH6)strongly ionized. With increase in HRr pressurc. 01' dccrease in temperature, i t i t h e abscxice of solid .l)', Brown and Pearsall ( $ 2 ) liavc shuicn that, in the absence of liydrogen chloride and at low temperature (-80" C.), purified aluminum chloride neither reacts with nor dissolves apprcciablj. HC1, the aluminum chloridc in toluene. In the presence OF e x ciisolves in toluene with the formation of a clear, brilliant gree~i solution, The reaction is reversible, in t.llat removal of HCI precipitates the aluniinum chloride and the toluene i? W ( X J V P W ~ unchanged. At, -80" one mole of IICl appears to conilii~io with oiie niole of AIC4, and the reaction is believed to involve the format,ion of a carlmniuni ion salt of Lhi: hypothrticnl ;arid IE.41Cla
e.
CH3CCHj $. HCI
+ '/2.4lz(Jlc,
[CHsCsEISj +[.4l('ljl
At -46.4" C. one inole of H(11 is tekeri up for each two ulolw of AlC1, CH3COH5 $. EICI
~
+ ,ilJ.?lb
=
jCH3C,H,] +[.4lZCl,J
Urown and Pearsall (B) rlladti it further pertirient prop( that these ternary complexes not, only act as solvents for e aluminum halides with the format,ion of complexes of the yeiit.~.a! formula R+[A1X4,nSlX3j --,but that they also play an important role i n most Friedel-Crafts reactions by furnishiiig ii higlilj, polar medium in which ionic intermediates may form iind rrirc:1, McCaulay and Lien ( 6 1 ) obtained greater efficienca>- ill the isomerization of xylenes using t,lie cat,alyst,, RFa-HF. This catalyst showed an adviintagc in t,his study over the ol.lit:i. Friedel-Crafts catalysts of the, .IICl,-HCl or A1Br3-RRl~ type inaPmuch as the hgdrogori halide component, HF, u;as ii liquid and could be used in excess to insure a constant activity and to serve as a high dielectric reaction solvent. I n ~ l o a dof using an excess of & l e x acatalyst,, these investigators mdintained a rahio of 6 moles HE" per mole of pure o-, nz-, or p-xylene. Fqiiilibriuni mixtures were obtained that then varied wit,li thc niolar ratios of BF8/xylene. Theso equilibrium compositiorw were independent of the temperature in ranges of 82" to 121' C. Yl'ilh catalytic amounts of BF8 (0.06 to 0.13 moles/niole xqlcrie), the equilibrium compositions agree closely wit8hthose calrulxtoti by Taylor ( 7 9 ) . o-Xylene rn-Xylene p-Xylene
80' C., 18 68
7%
24 ___ 100
1200
c., % 18 57
24 100
As the BFJxylene ratio wcli increased, the m-xylene con1 OII C ul the resulting product increased and in one run where the molar ratio of BF3/xylene was 3:1, p-Yylene was isomerized 100% to m-x y lene. The same authors also denionstrated that, under similar reaction conditions in the trimethylbenzene series where the equilibrium composition shows the mesitylene (1,3,5-) content to
Vol. 46, No. 9
alyst, thc: aniwnt of tuesityleiie i oncentratioii uutil, :it n molar of the trimothpl1,c:riaent~ isomerization in Llit, tc.1 ra-dominant. isomer is tlulrnr ace? of ca,talysl, witli mow I ~ c r i e(1,2,3,5-)was the only tetramct~hylbenzeneisomer d(,tc.cted. S a the length of t , l i ( , sitir chain increased (e.g. c'thylbenzene and propylhcnzcne), disproportionation into beiizcm? itrid polyalkylbenzenes took p h w under conditions which did not affect thr methyl dcrivatives. Baddeley and Pendlcton ( 5 ) have studied the isomcrimtiotr 01 o-allrglnrylkct'ones by aluminum chloride. In all instaiiccs, orit: niolt,cular proportion of alumintim halide conibines with Ihe cnrhonyl group t,o form :tn osonium complex ant1 :tiidif~iorial aluminum chloride is needed t.o cxffect the isomerizatior,. Tlir o-alkylarylketones iii contrast 1.0 ot,hcr allrylarylkctonos Iwoint. unstable a t 80' to 150" C. in the presence of hydrogv ;inti excesfi aluminum halide and undergo a variet>yof irr changes. The actlion of aluminum chloride on 3 kct.or :ind ported; a c e t y h m ~ ~ (2,~,R,6-1ct~ramcthq-lacetoplic~iioiiei e 9-acet,yl-s-octah~~droant~i~acerie and -phenanthrene, rviiicii Irnvca only one aromat'ic nuclear positioii occupied by a hydrogen B t80ni The reaction between acetyldurene and excess of aluiiiiniini chloride a t 100" C. provides a mixture of acetylprehniteire (2,~,4,5-tetramct~hylacetophenone) (80%), diacetyldurene (1 0%), and aromatic hydrocarbon (10%); 3,4,5-trimethylacetophenone (75%) and hexamethylbenzenc (12%) were isolat,ed from the products of interaction a t 150" (1. At 100" C. 9-acctyl-s-octjahydroanthraceiie and 9-acet~l-s-octahydrophena.nthrene iifford 7-acetyl-2-methyl-4: 5-r:!.clohexrnoindane in i 5 to 80% yield. The relative basicities ol the polyalkylacetophenoiies or of the 1: L AlCll oxonium complexes arc not established and t,herefore there is a queation as to whether the general rule wiicwning isomerization of alkylbenzeiie.: is applicable whm acyl groups are also eubstituents of t>hearoniatic nucleuil. oportionation requires more vigorous coiiditioiis tlian stion for any one aromatic derivative. Disproport,i .educt distribution and disproportionation rates n stmudiedby Lien and McCanlay (58) using ethyl henxcne, dicthyl benzene and m-xylene in the system BFI-EIF wing an excess of €IF. They found that, in the presence of excess €36'3, ethylbenzenr is about, 9S% converted a t 0' C. into benzene and dirt1i.lhenzeno, containing practically 100% metfa isomer. Thi: equilibrium consta,nt for the disproportionation txvrctioil
is defined as K = I:\ (benzene) -V (diethplbenzene)!Ss (ethyl-. hCnZeJle), where Ar is the mole Iraction. The value of K calculated from this experiment is 89. However with minor fminunts of ~ F (0.1 J t o 0.2 mole) fop value of K was within the range of 0.21 t o 0.31, and there was at, the same time a,n applicable amount of triethylbenzene formed. This increase of SO0 to 400-fold in the value of I< and the predominant tn-diethylbenzene obtained witli e x m e BF; (and e authors attribut,e t o the preferential formation of a coml)lex of m-diethplbenzene with BFs - HF, forming a positively charged I - I ~ )BFd-. ~ An ethyl group migrating cation, [ m - C S H ~ ( C ~ .H] from ethyl- or diethylbenzene bears a positive charge sild hence Rill not react with another cation, b u t it will attack t h e unconiplexed benzene and ethylbenzene. With a deficiency of IWa, considerable diethylbenzene remains uncomplexed and will therefore react with a migrating ct'hy! group to form triethylbenzcne. rn-Xylene was chosen for the disproportionation rate shdies because the migration of methyl groups was shown t,o be muc,h slower than that of the higher homologs. The rate of disproportionation increases with increasing boron trifluoride concentration and with temperature. +
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
September 1954
Lien and McCaulay (6.9) also studied the mechanism of alhyl-group transfer by disproportionation of 6 alkylbenzenes in the presence of excess hydrogen fluoride and boron trifluoride. In rxperiments a t room temperaturc with alkylbenzenes containing n-propyl, n-butyl, and s-butyl group8, the alkyl group maintained its configuration while transferring from one ring to another. These results indicate that the migrating alkyl group, before its bond with the first ring was broken, formed a partial bond to the second aromatic ring Otherwise the free alkyl carbonium ion would have isomerized to the more stable seconclary or tertiary configuration. The following mechanism is therefore proposed: Thr first step is the rapid and reversible addition of a proton, furnished by the acid catalyst, to the allrylbenzene at the ring carbon atom holding one of the alkyl groups. The aromatic cation formed is a u-complex ( 8 0 ) 11 I
I
+
H u-Coniplc'\
The u-Lomplex, for convenic.ncr, form
iq
"\/ \ /H C ,+C
&
c,,1
\(*/
\H
I
FI The second step is an S,2 displticc.nic~~tof an arene from the cation by another arene
H
H
I
c
UfC
C A H/ \C/
I
H\ c:/C\P
I
__.
C-13
A,
-
I
H
lf\/c\/H
i
/"
H\
II
c
c \H
FI '\C/ I
H Methyl substitution a t the a-carbon atom of the migrating alkyl group increases the stability of the transition state heca,use of hyperconjugation. This lowering of the t>ranFition-statcenergy accounts for the fact that ethylbenzene disproportionates more readily than toluene, and terkbutylbenzene more readily than ethylbenzene (58) whereas the neopentylbenzene was unconverted. Presumably the lert-butyl segment of the nropcnt,yl group sterically interferes with the approach of the second arcnr and thereby prevents reaction. At higher temperatures however t,he mechanism changes and the arene cation dissociate8 unimolecularly into an arene and an alkylcarbonium ion. Disproportionation by this mechanism is accompanied by a consideral~lr amount of side reactions and may leRd to a complex product.
denoted by the shortcmrd
H H \ /
H/'
H
COMPLEXES In addition to the ternary complexes reviewed above, complctxcp of the types A1Xs.ArH and AIX3.AlkX have been further investigated. Eley and King (41) have assigned t h e formnla, C ~ H ~ A I Bto r ~the , solid complex which they obtained, having an incongruent melting point of 37' C. The investigations of Brown and covorkers (20, 23) indicate that this is not neces~arily the case. I n fact, their results establish that aluminum bromide exists in aromatic hydrocarbon complexes in dimeric form and there is a weak interaction between the s electron^ of t,lioaromatic. system and the AlzBr, whirli can be formulated
ir
ll/'
1829
f c -
ll
C
H/ \C/
\H
I I
1
H
I..
Initial state H
\R
This complex is similar to those which they also established for the ullcyl homologs of benzene. They pointed out, however, that, contrary t o previous proposals there is no evidence to suggest that thew r complexes play any signifirant role. in thc. E'riedclCrafts reaction. Contrary to numerous patent refewncw, Ihow-n snd coworliws (2.9) have found that aluminum chloride is only slightly soluble in CHaCl a t -31.3" C. and no evidence of complex format,ion was observed. In contrast to the hchavior of the chloride, AIBra and A113 dissolved readily in the corresponding alkyl halides. I n alysis of the data indicated that AIBrp exists in methyl bromide solution as a 1 : l complcx, CI13Br:AlBr3, and ethyl bromide also forms a 1:1 complex with AIBrs. These author8 point out that these addition compounds q q a r e n t l y exist primarily in unionized form and undergo ionization s l o ~ ~ l yif: iit all. It follows that, the initial stage in Friedel-Crafts reactions ivith alkyl halides probably involvcs the forniatiou of these addition compounds with the ionization represented as a possil)le, but not essential, second stage.
RX
+ MX, e RX:MX8
RX : MX$ + R +krx4It
Transition state
= alkyl
ALKYLATION There is little doubt that alkylation of monoalkylbenzenes under selected conditions is accompanied by the formation of relatively large amounts of the meta substitution products ( 2 3 ) . Forguson (44)considered this to be an anomaly in view of the
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
1830
almost exclusive ortho-para orientation observed in other substitution reactions of these aromatics. Fierens ( 4 5 ) has also pointed out that care is necessary in applying the electronic theory to organic reactions where multiple reaction mechanisms occur such as the Friedel-Crafts methylation of toluene where the effects obtained are contrary to those predicted by the electronic theory. Since FeCb promotes p-alkylation and AlCla results in malkylation, it is not clear whether ortho and para substitution products might not be first formed with hlC& as catalyst followed by isoinerization to the meta substitution products. Mosby has called attention to an analogous case with acenaphthene (69). When acenaphthene is alkylated by a Friedel-Crafts reaction with terf-butyl chloride using FeC13 as the catalyst, para substitution takes place ( a t the 5-position) whereas with aluminum chloride meta substitution takes place (at the Cposition). Isomerization in the monoalkylacenaphthene series has not been thoroughly studied, but probably substitution takes place initially in the para position with both FeCla and -4lCls folloaed by isomerization in the case of the AlCls catalyst. Brown and associates (25) have emphasized the importance of the structure of the alkyl halide. The carbonium ion mechanism is no longer applicable to all Friedel-Crafts alkylations. I n the case of tertiary halides which form carbonium ions very readily this mechanism is the most probable, but with primary halides other interpretations are in order. For example, under highly acidic conditions that mould be proper for isomerization, ( 4 , 6Ql 61 ) n-propyl derivatives fail to give any isopropyl compounds. According to the explanation advanced by Brown ( d 5 ) the npropylbenzeiie arises from the displacement mechanism.
On the other hand formation of isopropylbenzene from the same reactants under more strenuous conditions involves the rearrangement to the more stable secondary carbonium ion. From their relative ease of formation by the action of FriedelCrafts catalysts on the halides, the st,ability of carbonium ions apparently increases in the order C2Hs+ < (CHa)&H+ < (CH&C+ < CHsCO+. According to the interpretation of this study, ( 2 3 ) t.he greater the stability of these carbonium ions, the less the reactivity and the greater the selectivity. The ethyl ion would therefore have the greatcst tendency of these substituents to form the meta-isomer and the acetyl ion would give the least proportion of the meta-isomer. Hennion's ( 5 1 ) experimental reeulb, obtained under conditions that do not provoke isomerization or dieproportionat'ion, agree with this theory, that, tert-butylat'ion of a monoalkyl benzene should yield a smaller proportion of the met'a derivative than does isopropy:ation. Brovn and coworkers (23) have also made exploratory studies of the rate of alkylation of aromatic hydrocarbons by substitut,ed benzyl halides. When 3,4dichlorobenxyl chloride, which reacts a t a convenient rate, was used for the study, it was observed that the reaction vias of the third order-Le., first order in aluminum chloride, first order in the benzyl chloride] and first order in benzene. Rate
=
K3[A1C&][RCl] [C&]
Moreover, the rate depends not only on the concentration of the aromatic component but increases with increasing basic properties of the aromatic component (the number in parentheses gives the relative rate const'ant a t 23" C.) ClCsH, (0,4i), CsHs
Val. 46,No. 9
(1.00), CH~CGHS(1.64)) m-(CI&)s CsHi (2.08). These values are also in relative agreement with those determined by Condon (36). The data are consistent with a mechanism involving a ratcdetermining nucleophilic attack by the aromatic component on thr benzyl halide-aluminum chloride complex
[."I
-4rH i- RC1:A41C133 Ar H---R---Cl:A1Cl8~ activated complex R'
[ +
AlClr-
+ ArR
f A1C13
+m-
+ HCl
\R
I n this preparation of 3,4-dichlorodiphenylmethane, from 3,4-dichlorobenzylchlorideand in an analogous preparation of 4-nitrodiphenylmethane, the reaction vas found to be not very sensitive to the dielectric constant of the medium. These results definitely rule out any mechanism based on a rate-determining ionization of the benzyl halide followed by rapid attack of the carbonium ion upon the aromatic. Moreover, rapid ionization of the halide followed by a rate-determining electrophilic displacement on aromatic carbon is improbable, since the p-nitrobenzyl carbonium ion should be more reactivc than the unsubstituted ion and its reaction should proceed a t a faster rate, whereas actually it is slower. The reversibility of the Friedel-Crafts alkylation reaction is illustrated by Fuson and Coolre ( 4 6 ) in the transformation of various types of substituted styrgl compounds such as 4,4'-dihaloetilbenes into 1,1,2 triphenyl ethane and 4carbomethoxystilbene into 1,1-diphenyl-2-p-carbomethoxyphenylethaneirj the presence of CaHa, HCl, and AlCL a t room temperature. The process involves the replacement of a halophenyl radical by a phenyl radical.
Mason and Gist ( 6 4 ) have contributed to the understanding of the Friedel-Crafts alkylation of benzene wit,h alkoxychloro-. alkanes. The behavior of alkoxychloroallianes in a FriedclCrafts reaction with benzene under varying condibions is used to explain the apparent discrepancies found in the earlier literature. The reaction does not take place through disporportionation of the alkoxychloromethane since dichloromethane could not be isolated when using butoxychloroniethane, and dibut'oxymethane does not react in the Friedel-Crafts reaction under conditions comparable with those used for the alkoxychloromet,hanes. Under similar conditions alkoxychloromethanes and alkoxy-lchloroethanes give analogous reactions, a fact which indicates t'hat the mechanism of the reaction does not involve the climination of hydrogen chloride to give an intermediate vinyl ether. The chlorine in alkoxy-1-chloroalkanes can react with benzene .It. low temperatures to give benzyl alkyl ethers, while under the same conditions necessary for its condensation, the latter also suffers rupture of the carbon-oxygen bond. The discrepancies in the earlier literature were found to be largely the result of different reaction conditions such as temperatures of reactions and concentrations of catalyst. Shorygina ( 7 6 ) studied the condensat'ion of ethylene oxide with benzene homologs, forming p-hydroxyethyl toluene, by passage of air containing ethylene oxide vapor (1.7 molee) into a mixture of 0.38 mole 41C13 and 1.6 moles of toluene over a period of 4 to 5 hours; yields n-ere generally about 30y0 a t 5' t o 10' C. At 10" to 15' C. the yield dropped to 1070; apparently the ratc of polymerization of the ethylene oxide was greater t,han t,he rate of condensation. tert-Amyl benzene is best prepared both from the standpoint of yield and purity, by the Friedel-Crafts reaction of tert-amyl
September 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
chloride and benzene when catalyzed with anhydrous FeCL (66). Aluminum chloride gave a product consisting of a mixture of isomeric amyl benzenes. I n studying the alkylation of 2,5-dimethylthiophene with various alkyl halides (0.5 mole proportions) by adding these mixtures dropwise to a solution of AlCla in carbon disulfide a t 0' C. for 10 hours, Messina and Brown (66) found that the 2,5dimethylthiophene alkylated readily with tert-butyl chloride forming only a minor amount of polymer. With less active halides such as n-butyl chloride, some replacement of the alkyl group occurred and polymerization increased. Nosby (66) has condensed yvalerolactone by the FriedelCrafts reaction with each of the isomeric xylenes, using excess xylene as the solvent and 1.05 moles AlCls as the catalyst. The resulting 4-(dimethylphenyl)-pentanoic acids were cyclized to trimethyl-1-tetralones in good yield. Cyclization of 4-(2,4 dimethylphenyl)-pentanoic acid using polyphosphoric acid was accomplished by a rearrangement resulting in 4,6,8-trimethyl-ltetralone whereas the Friedel-Crafts cyclization of the corresponding acid chloride with stannic chloride gave the expected 4,5,7-trimethyl-l-tetralone. The rearrangement of 4(2,4-dimethylpheny1)-pentanoic acid involves the migration of the valeric acid moiety to a position of symmetry in the xylene ring, followed by cyclization. This explanation is supported by the observation that the 4,5,i-trimethyl-l-tetralone is unchanged by heating with polyphosphoric acid. The four trimethyl-l-tetralones were converted to four known trimethylnaphthalenes and to three tetramethylnaphthalenes, two of which are new. Durene was condensed with 7-valerolactone and the resulting pentanoic acid was cyclized to 4,5,6,7,8-pentamethyl-l-tetralone.From this tetralone were prepared 1,2,3,4,5-pentamethylnaphthalene and 1,2,3,4,5,8-hexamethylnaphthalene. In a second paper, Mosby ( 6 7 ) condensed 7-valerolactone by the Friedel-Crafts reaction under similar conditions with tetralin and ring closed the resulting 4-substituted-pentanoic acid with polyphosphoric acid. The tetralone derivative was then converted to I-methyl- and 1,4-dimethyIanthracenes. Christian (36) studied the condensation of lactones with benzene a t room temperature using AlCla as the catalyst. Using a ratio of approximately 1.2 to 1.4 moles A1Ch per mole of the appropriate lactone, yphenylbutyric acid, 7-phenylvaleric acid, and S-phenylvaleric acid were obtained in yields of 44, 61, and 5l%, respectively. Higher boiling fractions were obtained that were not further characterized. Truce and Olsen (82) studied the condensation of ybutyrolactone with benzene a t reflux temperature, in a series of experiments varying the amounts of -kIC13. Using amounts of AlCla comparable to those of Christian (si),a higher yield of yphenylbutyric acid was obtained (73%) as well as 11% of the ring-closed product, a-tetralone. As the molar ratio of A1Cl3:lactone was increased, the amount of atetralone increased and the amount of yphenylbutyric acid decreased, until a t a molar ratio of 2.50, a yield of 66% a-tetralone was obtained and no y-phenylbutyric acid was isolated from the brown residue.
ACYLATION Bruce and coworkers ( 2 4 )have determined that condensation of hydroquinone with ybutyro-lactone gave 4,7-hydroxy-3-methylindanone and not the expected 5,8-dihydroxy-tetralone in fused aluminum chloride-sodium chloride melts a t 180" to 200" C. Apparently under these more strenuous conditions the lactone ring opens to form a carbonium ion on the carbonyl group which condenses to the intermediate ketone and this then ring closes by the elimination of the alcoholic group and shift of the double bond. Man and Hauser (63) have made a systematic study of the relative reactivities of certain acylating agents in the FriedelCrafts reaction including acetic anhydride, acetyl chloride, p-nitrophenyl acetate, acetic acid, benzoic anhydride, benzoyl
1831
chloride, p-nitrophenyl benzoate. With an excess of aluminum chloride in a solvent, acetic anhydride appears to be more reactive than acetyl chloride in the acetylation of bromobenzene but not in the acetylation of toluene. By means of competitive reactions between two acid chlorides for toluene or anisole they have found that the relative reactivities of the acid chlorides decrease in the order acetyl chloride > benzoyl chloride > 2ethylbutyryl chloride. Similarly, p-nitrophenyl acetate was found more reactive than p-nitrophenyl benzoate. Benzoyl chloride and p-nitrophenyl acetate were found to undergo exchange to form p-nitrophenyl benzoate and acetyl chloride. Fuson and House ( 4 7 ) have prepared diacetyl m-xylene by means of the Friedel-Crafts reaction. A large excess of aluminum chloride added to a solution of 3,5-dimethylacetanilide and acetyl chloride in carbon disulfide gave 98% yield of tfie 4acetyl derivative. The acetylamino group was then removed to give the 2,6-dimethylacetophenone. Whereas the 2,4-dimethylacetophenone did not react, the 2,6-dimethylacetophenone did react under conditions similar to those described above to give approximately 55% of the 2,4dimethyl-l,3-diacetylbenzene. Granger and coworkers (49) studied the acylation of salicylamide in nitrobenzene with 2.6 moles of aluminum chloride a t 20" C. forming the 5-acetylsalicylamide. The Fries rearrangement takes place a t higher temperatures. Haloacetylation is much more difficult than ordinary acetylation-for example, in nitrobenzene, monochloroacetyl chloride does not react a t 20' C. with salicylamide, but a t 80' C. the 5-(chloroacetyl) salicylamide is formed. The Fries rearrangement is more limited with chloroacetyl derivatives, and therefore no rearrangement takes place a t this temperature. Bassilios and Salem (15) have made a systematic study of the acetylation of naphthalene with acetyl chloride by the FriedelCrafts method using 121C13 as the catalyst. The following methods were used: 1. Slow addition of aluminum chloride to a naphthaleneacetyl chloride mixture 2. Addition of aluminum chloride-acetyl chloride complex to naphthalene 3. Addition of acetyl chloride to a naphthalene-aluminum chloride mixture 4. Addition of a naphthalene-acetyl chloride mixture to aluminum chloride. The results obtained were also influenced by the solvent. A mixture of monoisomers was obtained in each case, nitrobenzene giving a higher percentage of 0-isomer while carbon disulfide, monochlorobenzene, and ethylene dichloride favored the formation of the a-isomer. The optimum results were obtained with method 4 in carbon disulfide, monochlorobenzene, and mononitrobenzene and with method 2 in ethylene dichloride. Taylor and Watts (80) studied the acetylation of p-alkyl derivatives of toluene including the p-ethyl-, p-n-propyl-, p-isopropyl-, and p-tert-butyl-toluenes by the Friedel-Crafts reaction using 1 mole of acetic anhydride and 3.5 moles of aluminum chloride in carbon disulfide. The 5-ethyl-2-methylacetophenene, 5-npropyl-2-methylacetophenone, and 5-isopropyl-2-methylacetophenone were obtained as expected. The p-lertbutyltoluene, however, gave the 4-tertbutyl-2-methylacetophenone instead of the expected 5-terl-butyl-2-methylacetophenone, indicating the tert-butyl group had migrated from the para to the mcta position relative to the methyl group. Unless conditions were carefully controlled, the acetylations resulted in replacement of the tertbutyl group by the acetyl group, instead of the migration. Borsche and coworkers ( 1 7 ) have used the Friedel-Crafts acylation reaction to determine whether coumarins are inert esters of phenol, in which case they should be readily acylated according to the Friedel-Crafts reaction or are benzene derivatives with an unsaturated side chain in which case the benzo ring is protected against acylation. Actually coumarin was not acylated with either acetyl chloride, benzoyl chloride, or phenyl
1832
INDUSTRIAL AND ENGINEERING CHEMISTRY
acrtj-1 chloride in nitrobenzene using aluminum chloride as cataly,5t,and therefore, tlic latter possibility is true. As further proof, it v a s determined that hydrocoumarin vias acylated under similar conditions with each of these acyl chlorides. Buu-Hoi and coworkers ( 3 1 ) have made an estensi the action of aluminum chloride under Friedel-Crafts conditions on various acid chlorides capable of undergoing cyclization. By varying the aromatic solvent, the ease of formation of yomc 5- and 6-membered-ring ketones can thus be estimated from the comparative amounts of competitive formation of open-chain ketones, as premnted in a table. The acid chlorides include B-phenylpropionyl-, b-p-tolylpropionyl-, 8-p-cliloroplienylpropionyl-, y-phenylbutyryl-, and I-naphthylacetylchloride. The solvents include benzene, ethylbenzenn, diphenyl, chlorohenzene, anisole, thiophene, 2 :5-dimethylthiophene, and veratrole. The result,s also indicate the effect of the substituent groups on the reactivity of the various compounds in the Friedel-Crafts ket,one synthesis, and these agree in general with earlier result,s obtained by other methods. Kimoto and Asaki (54)have determined Chat 3-methoxydiphenylether, when reacted with acetyl chloride and aluminum chloride in carbon disulfide, was part)ially demethylated to form a mixture of the 4-acetyl-3-hydroxydiphenyletherand the corresponding niethoxy compound. TT'lien the 3-nletll~.ldipllrmylether is reacted under similar condit,ions, thr 4-acetyl compound results. The reaction of the 4-met.hosy-4'-niethyldiplieriylether and acetyl chloride occurs chiefly in the position ortho to the methoxy group. Ruu-Hof and associates (32 j hare determined that t,ripheiiylenc is subetitut,ed a t the 2-position in Friedel-Crafts acylntionq with acyl chlorides and aluminum chloride in carbon disulfide. BuuHoi and Xuong (33) have used the Friedel-Crafts acylation of nz- and p-fluorotoluene in the preparation oE intermediates for the synthesis of carcinogenic nitrogen compounds. They have proved that acplation ol the m-fluorotolucne results in substitution para to the CHs group and they assume by analogy that substitution occurs ortho to the CI€a group in the p-fluorot,oluene. p-Resorcylic acid amide or arylamide ( 3 4 ) when rea,cted with 1 mole of acetic anhydride and 2 moles of aluminum chloride in nitrobenzene are acetylated entirely in the 5-position. Englert, and coworkers ( 4 2 ) ha7.e determined that the most satisfactory method of preparation of aralkyl ketones having long-chain alkyl components TTas by the Friedel-Crafts condensation of the long-chain acyl chloride v i t h the aromatic compound. This Kas followed by cat'alytic hydrogenation t o form detergent intermediates. Schoental (74) condensed anthracene and succinic anhydride in the presence of aluminum chloride in cold methylene chloride in molecular proportions and obt,ained a mixture from which all three theoretically possible anthroylpropionic acids have been isolated and identified. When one to two moles of aluminum chloride were used, about half of the anthracene remained unchanged; but use of two moles each of succinic anhydride and aluminum chloride resulted in almost complete tranPEorniation of anthracene int,o acidic products which, however, m r e not isolated nor identified because of the complexity of the mixture. Barnes and associates (13)have determined that Friedel-Crafts acylation reactions with 4a-methyl-l,2,3,4,4a:9,10, loa-octahydrophenanthrene take place almost exclusively a t the 6-position. Buu-Ho'i and Hoan (30) have studied the acylation of dibenzoselenophene with both acetyl chloride and acetic anhydride in carbon disulfide using aluminum chloride as catalyst. TT7ith acetyl chloride a yield of approximately 25% of theory vias obtained, but with acetic anhydride the yield was lower arid 2 moles of aluminum chloride were required. Takegami and Shingu (78) have deterniined that. ethyl acetate is decomposed only 4 to 9% in the presence of excess aluminum bromide without any formation of ethyl bromide. Kinet'ic studies showed that the rate of acylation of aromatic hydrocar-
Vol. 46,No. 9
bons vi-ith organic esters was of tlic f r s t order v i t h respect t,o the ester and its rate coristrtiit was proportional to the concentration of free aluminum bromide. The following mechanism is suggested. 1. Only the free altaniinuiii broniidc has cat,alytic activity (the ester-aluminum bio!nide complex is cabalytically inactive). 2 . The acetyl catioii may be forincd b y the interaction of free aluminum bromide arid the ester-aluminum bromide complex. 3. The acyl cation acylates the benzene and never produces acyl halide. The rate of acetylation is affected by thc structure of the estmer8-e.g., AcOEt 0.41, AcOPr 0.82, and AcOBu 0.85 Inin.-1 per mole ester per mole of aluminum bromide. This order of reaction rate agrees with that of the corresponding alkyl halide and indicates that the inductive effect of the alkyl group facilitates the attack of aluminum bromide on the oxygen atom of the alkoxy group. The order of react,ion rates is also affected by the structure of the acid-e.g., HCOzEt 2.07, AcOEt 0.41, m d PrC02Et' 0.084. This indicat'es that the strength of the OEt bond is l i k m i w increased by the inductive effect of the alkyl group in the acid residue. Rnddeley and coworkers (3)have found that a t least one derivative of anthraquinone is obtained when each of a scries ol' benzoylbenzoic acids substituted in the ortho position is treated with aluminum chloride. Some of the acids are ausceptible to isomerization and give anthraquinones after migration of substituents. For example, o-(2,4,6-trimethylbenxoyl)- and o(2,3,5,6-tetran~?thylbenzoyl)benzoic acid by the shifting of the alkyl groups readily give ieomeric acids which are then amenable to ring closure. o-(6-Hydroxy-2,4-dimethylbenzoyl)and 0-(2,4 dialkyl-6-hydroxybenzoyl) benzoic acids can be cyclized t o the corresponding 1,2-dialky1-4-hydroxyanthraquinones.Ring closures effected through sulfuric acid were not accompanied by isomerization and provided anthraquiaoncs t'hat \- 6-, and 7-mcmbercd rings. dttempt,s to form 4- and 8-membered rings were unsuccessful. Results in the Fricdel-Crafts cyclizations were dependent on the solsent and cat,alyst employed. Stannic chloride in syintetrachloroethane was not sufficiently active for the reaction to occur. Aluminum chloride in the same solvent resulted in decomposition products. However, satisfactory reactions were obtained when aluminum chloride (1.1 to 1.5 mole) was employed with nitrobenzene as the solvent a t ternperaturcs ranging from 7 " to 100". The results are
n n n
n n
Yields, % = l 0 = 2 35-37 = 3 62-76 = 4 29-31 5 =5 0
Y
Kosolapoff (55) has studied the orientation of phosphorus in the Friedel-Crafts reaction of toluene and phosphorous trichloride, by gently refluxing in the presence of aluminum chloride as a catalyst. The isomers forined were 10% o-, 2iy0 m-, and 63y0 toluene dichlorophosphines. Cullinane and coworkers (37-38) have studied the effect of titanium tetrachloride, as catalyst in the Friedel-Crafts reaction I n studying the acylation of aromatic hydrocarbons, 2 to 3 equivalents of titanium tetrachloride give the best yields with
September 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
either acids, acid chlorides, or acid anhydrides. The ease of reaction with the aromatic component was of the order benzene, toluene, and anisole. In the case of toluene and anisole, the para substitution products were formed. With acyl chlorides the yields of ketones increased in the order acetyl, n-propionyl, n-butyryl, and benzoyl. The unreactivity of benzene with phthalic anhydride seemed to be an exception, because in this case no reaction took place, whereas with toluene, 3,3-di-ptolylphthalide was the chief product. Solid complexes of titanium tetrachloride and the acylchlorides were prepared having the general formula of TiC1:. RCOCl. Thermal analysis indicated that titanium tetmchloride and benzene form a complex 3TiC14. CeHs. Addition compounds of the titanium tetrachloride and the ketones prepared by the above reaction were also isolated and identified. Reinheimer and Smith ( T I ) have proposed the use of the Friedel-Crafts reaction in qualitative organic chemistry where aromatic ethers are identified by acylation with succinic anhydride in the presence of aluminum chloride in a mixture of acetylenetetrachloride and nitrobenzene as solvents. The resulting aroylpropionic acids are isolated in a conventional manner and identified by melting points. An interesting rearrangement of a,@,-dimethyldibenzyl (Iphenyl-2-methyl-2-phenylpropane) in the presence of aluminum chloride has been reported by Sonierville and Spoerri (77). d,Z-2,3-Diphenylbutane was shown to be converted to the mesoisomer in the presence of aluminum chloride, the extent of the conversion depending upon the temperature and amount of aluminum chloride. A similar conversion also occurred with concentrated sulfuric acid. Likewiae, both neophyl chloride (2-methyl-2-phenyl-1 propane chloride) and 2-benzyl-2-propane chloride yielded a mixture of l-phenyl-2-methyl-2-phenylpropane and meso-2,3-diphenylbutane when condensed with aluminum chloride and benzene. In studying the mechanism of the rearrangement, l-phenyl-2-methyl-2-phenylpropanewas treated with aluminum chloride using both chlorobenzene and toluene as solvents. The solvent has been shown to participate in the rearrangement indicating that the reaction is intermolecular. Mechanisms which are consistent with the experimental data are presented which are preceeded by cleavage of the l-pheny1-2methyl-2-phenylpropane molecule involving ionization and a lJ2-phenyl shift as well as a lJ2-methyl shift on the ethane carbons. The para-tolyl group was much more reactive in the rearrangement in toluene solution than was the phenyl group in benzene solution. The formation of both isobutylbenzene and p-isobutyltoluene from the corresponding carbonium ions is explained by the removal of a hydride ion from another molecule of hydrocarbon. No isobutylbenzene was observed as a result of the rearrangement of the l-phenyl-2-methyl-2-phenylpropane in toluene solution. Rhattacharyya and coworkers ( 1 6 ) have studied the FriedelCrafts reaction between ethyl allyl acetate and hydrocarbons such as benzene, toluene, and m-xylene in the preeence of aluminum chloride at 0.5' C. I n the caw of toluene, for example, this reaction gave m-MeCBHa(CRz)t-COzEt. The structure was proved chemically b y conversion of the corresponding acid to the acid chloride, and then ring closure with aluminum chloride or stannic chloride to the corresponding tetralone. The meta orientation was proved by oxidation with permanganate to isophthalic acid. Krauss and Grund ( 6 7 ) have shown that the Friedel-Crafts reaction with BF3 and isobutylene does not take place without addition of a eo-catalyst like acetyl chloride or HC1 as initiator. The BFI itself is unable to polarize the C : C bond; the BFSC1complex ion, however, can do it. This initial stage was demonstrated by spectral study of the metal halide-alkylene, its main absorption band has considerable extinction. The metal halides used were BFa, FeCla, AlCla, SbClr, CdClt, and ZnClz. The C: 0 group or C: C group shows no reaction xith the metal halide catalyst even after 3 days but reacts almost at once after the
1833
co-catalyst is added. The co-catalysts were acet,yl chloride or
HC1 and are characterized generally as compounds that react wit>hmetal halides to form a,n "an-solvoJ' acid and add a cation or proton to the reaction. Traces of moisture may also act as a cocatalyst. The CHzOH group reacts directly with pure mrtal halides without the aid of a eo-catalyst. Ettel and associates (43) determined that niucochloric acid condensed stepwise with benzene in the presence of aluminum chloride catalyst to give 89% yield of r-phenyl-a,p-dichlorocrotonolactone, and y,-,-diphcnyl-a,p-dichlorocrotonic arid. When monochlorobenzene was used in place of benzene, the corresponding p-chlorophenyl derivatives mere formed. Xfukerji and Bhattacharyya ( 6 8 ) have presented a novel and convenient, method for the synthesis of phenanthrene derivative,s such as 1-methyl-, l,Cdimethyl-, and 9-nnethylphenanthrene, involving Friedel-Crafts react)ions with unsaturated Ice.. tones and esters. lJ4-Dimethylphenanthreneis synthesized by reading naphthalene in carbon disulfide solution witb allylacetone in the presence oE aluminum chloride to give 2-(P-napbthyl)hexan-5-one. This product was then reduced to the corresponding carbinol by means of the ~leerTvein-Pondorff-T'erley method (aluminum-isopropoxide j, ring closure with concentrat'ed sulfuric acid and dehydrogenation with Pd-C gave 1,4dimethylphenanthrene. I n a similar manner 1-methylphenthrene was prepared by condensing naphthalene and ethylnllylacetaie in carbon disulfide using aluminum chloride as the catalyst, t o form ethyl4-($-naphthyl)valeratje. This compound was t'hen ring c.losed with thionyl chloride and stannic chloride, reduced by the Clem-. mensen method with Zn-HC1, and dehydrogenated to l-methylphenanthrene. By an extension of the above method to benzene and 2-allylcyclohexanoncJ 2-(P-methyl-p-phenylethyl)cycloli~~~anone was obtained in excgllent yield. This product was reduced by aluminum isopropoxide to yield the corresponding cycloheuanol which was cyclized with concent,rated sulfuric acid and then dehydrogenated to give 9-methylphenanthrene. Braz (18) has introduced the 2-aminoethyl group irito tiir :ire-, matic ring by means of ethylenimine in the presence of an P:LCBPX of aluminum chloride. The reaction is highly exothermic and is carried out in a sealed tube heated to 120" to 130" C. or higher for 7 to 8 hours with shaking. At 170' to 180' C. yields of $0 to 80% were obtained with benzene. Unstated yields of P-aminoethyl derivatives were also obtained with ethylbenzene and anisole but Bimilar reactions did not take place with mononitrobensene. Apparently the ethylenimine reacts as a complex with thp tilu.. minum chloride.
COMMERCIAL APPLICATIONS Many commercially practical applications of the Friedel-Crafts reaction have been made during the past 2 years as indicated both by the diversity of subject matter and by the number of patents that are dependent upon this reaction. Considerable use of this reaction has been made in the field of phthalocyanines to prepare both direct and vattable dyes from the insoluble pigments. Badische Anilin- & Sodafabrik has been granted a series of these patents where phthalocyanines have been reacted in the presence of Friedel-Craftfi condensing agents with anhydrides of polybasic acids (7, I d ) , with r-butyrolactone (6) with halogenated aliphatic acids (IO), and with acyl chlorides such as phosgene, oxalyl chloride, or sulfuryl chlorids (9) to prepare either water-soluble dyes or vattable dyes Halomethylphthalocyanine derivatives have been obtained by Wood (85) by heating a phthalocyanine in the presence of aluminum chloride with a halomethylether preferably in the presence of a tertiary base such as triethylamine or pyridine. Haddock, Slinger, and Wood (60) have prepared green, water-soluble phthalo-cyanine dyes b y heating a copper tetrakis(p-tolylthio)phthalocyanine with bis(chloromethy1) ether a t 25' C. in the presence of aluminum chloride and nitrobenzene or aluminum
1834
INDUSTRIAL AND ENGINEERING CHEMISTRY
chloride and pyridine or in sulfuric acid and treating the resulting copper tris( chloromethyl)tetrakis(p toly1thio)phthalo cyanine with tetramethglthiourea. Parkinson and Wardleworth (70) have treated chloromethyl derivatives of anthraquinone-, iso-, perylene-, and dioxazine dyes with phenols in the presence of Friedel-Crafts catalyst such as zinc chloride to form new substantive dyestuffs. Ingram ( 5 3 ) has prepared antioxidants by heating 1.2-dihydroquinoline with an aralkyl chloride in the presence of a Friedel-Crafts catalyst. Shaver (76) has prepared a,p-unsaturated ketones as well as aralkyl carboxylic acids by treating aromatic hydrocarbons with aliphatic p-lactones and aluminum chloride in a Friedel-Crafts acylation type reaction. Goebbel (48)has made use of the Friedel-Crafts reaction by acylating a 2-ring aromatic compound such as diphenyloxide with 2 moles of a long-chain arid or acid derivatives to form products which are useful in the preparation of linear or lattice type polymers, (fibers, films, resins, elastomers). Butler ( 2 5 ) has acylated polystyrene by the Friedel-Craft2 reaction using aluminum chloride and a long-chain acyl chloride t o form polymeric resins suitable for use in coating compositions, adhesives, and lubricant additives Bruins (25, 26) has used the Friedel-Crafts acylation reaction to prepare esterified aromatic hydrocarbons by reacting a mole of an aromatic hydrocarbon with 1 mole of maleic anhydride and then esterifying the acid reaction product with 2-ethyl-1-hexanol. These are useful as plasticizers for vinyl resins Badische Anilin- & Sodafabrik (11) has prepared halogenaminoanthraquinones by treating aminoanthraquinones dissolved in molten anhydrous aluminum chloride which may contain a melting-point depressant such as sodium sulfite, with halogen Richter and Frey ( 7 2 ) have prepared diphenyl sulfone derivatives by treating aromatic sulfone chloiidee a i t h a reactive nromatic derivative in a solvent such as nitrobenzene, using aluminum chloride as the catalyst. Kosolapoff (56') has prepared phosphonic and phosphinic acids and their esters by treating aromatic hydrocarbons with phosphorous trichloride in the piesence of aluminum chloride, chlorinating the mixture of a halogenated solvent, and then treating mith an alcohol to obtain the desired ester. hIcCormack and Stilmar ( 6 2 ) have treated cobalt phthalocyanine in an aluminum chloride-sodium chloride melt a t 75' to 150' C. with phosphorous trichloride to introduce an average of 2 to 4 PC1, groups into each 10 molecules of pigment. The PClz groups were then hydrolyzed to P(0H)Z (phosphorous acid) groups to give vattable phthalocyanine dyes. Aschner (2) has piepared local anetthetic intermediates, u hich are derivatives of tetrahydloisoquinolone, by treating the reaction products of a 0-phenylethylamine and phosgene with a Friedel-Crafts type catalyst. Scalera and associates ( 7 3 ) have prepared naphthostyrils by treating 1-naphthylisocyanates and isothiocyanates, in which the 8-position is open, with a Friedel-Crafts catalyst in an inert liquid diluent and heating at 100" to 200" C. Danner and Zerweck (39) have prepared sulfurized vat dyestuffs and condensation products of the anthraquinone series by condensing the nitrogen free anthraquinone derivatives with sulfur dioxide in molten aluminum chloride. Young (84)has prepared low-moleculai ethylene polymers consisting predominantly of CIO-CZO straight-chain a-olefins by polymerization of ethylene in the presence of a Friedel-Crafts type catalyst, specifically an AlCb-C~H,Cl saturated solution a t a b mospheric pressure, contact being made in the vapor phase a t O0-2O0 C. Badische Anilin- & Sodafabrik (8) has introduced NHZ groups into polynulcear aromatic hydrocarbons, containing at least one of the groups, =C=O or =C=Nby treating with
-
-
Vol. 46, No. 9
HzNOH or its salts in an aluminum chloride-sodium chloride melt. British Thomson-Houston Co. Ltd. (29) has prepared organohalogenosilanes by heating hydrocarbons with halogenodisilanes in the presence of a Friedel-Crafts catalyst.
Barry (14) has prepared chlorosilanes from aromatic chlorides and trichlorosilanes in the presence of Friedel-Crafts catalysts such as aluminum chloride or boron chloride by heating in an autoclave at temperatures of approximately 290' C. A mixture of isomeric products is obtained. Alquist, Wasco, and Xauer ( 1 ) have converted polychlorocyclohexane containing 6 to 8 chlorine atoms t o a polychlorobenzene containing 3 to 5 chlorine atoms by heating with an anhydrous Friedel-Crafts catalyst such as aluminum chloride a t temperatures above 90" C. a t which 3 moles of hydrogen chloride are liberated per mole of polychlorocyclohexane.
LITERATURE CITED hlquist, F. 9., tVasco, J. L., and Kauer, K. C. (to Dow Cheniical Co.), Brit. Patent 694,275 (July 15, 1953). Aschner, T., (to Smith, Kline &- French), U. S. Patent 2,647,902 (huguet 4, 1953). Baddeley, G.. Holt, G., and Maker, S. M., J . Chem. Soc., 1952, pp. 2415-20. Baddeley, G., Holt, G., and Voss, D., Ibid., 1952, p. 100. Raddeley, G., and Pendleton, A. G., Ibid., 1952, pp. 807-12. Badische Anilin- & Sodafabrik, Brit. Patent 678,195 (August 2 7 , 1Y52).
679,808 (September 24, 1952). 680,511 (October 8, 1952). 688,784 (March 11, 1953). 688,785. 688,810. Badische Anilin- & Sodafabrik, French Patent 1,031,870 (June 26, 1953). Barnes, R. A,, and Gottesman, R. T., J . Am. Chenz. SOC.,74, 35-7 (1952). Barry, A. J. (to Dow Corning Ltd.), Brit. Patent 671,710 (>lay 7, 1952). Bassilios, H. F., and Salem, 8. Y., Bull. ~ O C .chim. France, 1952, pp. 586--92. Bhattacharyya, ?;. K., Singh, S., Vig, 0. P., and Mukherji, 8. &I., Science and Culture ( I n d i a ) , 18, 341-2 (1953). Borsche, W., and Hahn-~~eirilieirner, P., Chem. Ber., 85, 198 202 (1952). Braz. G. I.. Dokladv ALad. Yavk S.S.S.R.. 87. 589-92 (1952). British Thomson-Houston Co. Ltd., Brit. Patknt 684,639 (Der.
Ihid., Ibid., Ibid., Ihid., Ihid.,
24., 1952). ,
Brown, H. C., and Brady, J. D., J . Am. Cliem. Soc., 74, 3670 (1952). Brovn, H. C., and Pearsall, H. W., Ibid., 73, 4681 (1981). Ibid., 74, 191-5 (1952). Brown, H. C., Pearsall, H.W., Eddy, L. P., and asjociates, IKD. ENG.CHYIIM., 45, 1462 (1953). Bruce, D. B., Sorrie, S. J. A., and Thomson, R. K., J . Chem. Soc., 1953, p. 2403. Bruins, F. (to Socony-Vacuum), U. S. Patent 2,642,407 (.June 16, 1953). Ibid., 2,642,455. Burtner, R. (to Searle Co.), U. S. Patent 2,654,778 (Oct. 6, 1953).
Burton, €-I., Chemistry & Industry, 1954, p. 90. Butler, J. M. (to llonsanto Chemical Co.), U. S. Patent 2,642,398 (1953).
Buu-HOP, Kg. Ph., and Hoan, S g . , J . Org. Chem., 17, G43--7 (1952).
Buu-Hof, Ng. Ph., Hoan, Ng., and Xuong, Ng. D . , J . Chem. SOC.,1951, pp. 3499-502. Buu-Hoi', Ng. Ph., and Jacquignon, P., Ibid., 1953, pp. 941-2. Buu-Hoi, Ng. Ph., and Xuong, N. D., Ibid., 1953, pp. 386-8. Ryatnal, V. K., and Desai, R. D., J . I n d i a n Chem. Soc., 29, 555-9 (1952). Christian, R. V., Jr., J . Am. Chem. Soc., 74, 1591 (1952). Condon, F. E., Ibid.. 74, 2525 (1952). Cullinane, N. M., Chard, S . J., and Leyshon, D. h l . , J . Chem. SOC.,1952, p. 376. Ibid., pp. 41068.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
September 1954
(39) Danner, J. JI., and Zerweck, W., Brit. Patent 688,651 (March 11, 1953). (40) Eley, D. D., and King, P. J., J . Chem. Soc., 1952, p. 2517. (41) Eley, D. D., and King, P. J., Trans. Faraday SOC.,47, 1287 (1951). (42) Englert, R. D., and associates, J . Am. Oil Chemists' SOC.,30, 337-9 (1953). (43) Ettel, V., and associates, Chem. Listy, 46, 232-7 (1952). (44) Ferguson, L. N., Chem. Eews., 50, 47 (1952). (46) Fierens. P. J. C.. Industrie ehim. belae. 17. 3-8 (1953). (46j Fuson, R. C., and Cooke, H. G., jr., J . Am.'Chem. Soc., 73, * 3515-16 (1951). (47) Fuson, R. C., and Rouse, H. O., J . Org. Chem., 18, 496-500 (1953). (48) Goebbel, C. G. (to Emery Industries, Inc.), U. S: Patent 2,573,433 (Oct. 30, 1951). (49) Granger, R., and associates, Compt. Rend., 234, 1058-60 (1982). (50) Haddock, N. H., Slinger. F. H., Wood, C. and Imperial Chemical Industries, Ltd., Brit. Patent 686,391 (Jan. 21, 1953). (51) Hennion, G. F., and associates, J . Org. Chem., 17, 1102 (1952). (52) Inatome, M.,and associates, J . Am. Chem. Soc., 74, 292-5 (1952). (53) Ingram, J. (to Monsanto), U. S. Patent 2,626,253 (Jan. 20, 1953). 154) Kimoto, S.,and Asaki, K., J . Pharm. SOC.J a p a n , 72, 300-3 (1952). (55) Kosolapoff, G. VI.,J . Am. Chem. Soc., 74, 4119-20 (1952). (56) Kosolapoff. G. M. (to Monsanto Chemical Co.), U. S. Patent 2,594,454 (April 29, 1952). (57) Krauss, W., and Grund, H., ~ ~ a t u r w i s s e n s c h u f t e n40, , 18-19 (1953). (58) Lien, A. P., and McCaulay, D. A., J . Am. Chem. Soc., 75, 2407 (1953). (59) Ibid., p. 2411. (60) ;\IcCaulay, D. A., and Lien, A. P., Ibid., 73, 2013 (1951). (61) Ibid., 74, 6246 (1952). (62) AlcCormack, 1%'. H., and Stilmar, F. B. (to Du Pont), U. S. Patent 2,613,129 (Oct. 7 , 1952).
1835
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HALOGENATION OGDEN R. PIERCE, DOW CORNING CORP., MIDLAND, MICH. Commercial production OF halogens and halogen acids is still at a high level and shows an increase over the previous year. Production OF chlorinated organic compounds is slightly lower than previously. In the field of chlorination research, process improvements have received much attention with emphasis on preparation of olefins and polymers. Fluorination research has been devoted primarily to synthesis of olefins and a study of polymerization techniques. Considerable work has been done in the area OF oxygen-containing compounds, especially esters. The field of bromination has not been extensively studied and is concerned with aliphatic and aromatic hydrocarbons. Iodination still remains the least explored area of halogenation and only a few investigations are reported.
T
HE production of chlorine, hydrogen chloride, and hydrogen fluoride has increased during the past gear as shown in the comparative total tonnages for the years 1952 and 1953 1952
Clz HC1
HF
1953
(Short Tons)
(Short Tons)
2,608,690 683,742 41,512
2,796,070 771,241 51,048
The production of chlorinated organic compounds has shown a slight decline over the previous year. The total production figures are given below (47A). CCla CaHsCl c2c14 CzHC13
1953 (Lb.) 239 206 384 356:417 :276 151,666,704 324,751,572
CsHeCls
DDT 2,4-D
2,4,5-T
1953 (Lb.) 59,793,110 83,981,474 25,214,630 5,112,129
CHLORINATION PARAFFIN HYDROCARBONS
Chlorination of methane (bA) a t 1500 to 4500 c. in the presence of ultraviolet light at a tirne of 5 minutes produced tetrachloroethvlene (35% conversion) as well as a high yield of carbon tetrachloride. A commercial process for the chlorination of methane (3'5A) yields an 85 to 90% conversion of methane to chlorinated products a t 650" to 700' F. By varying the reaction conditions a desirable product distribution may be obtained. Reaction of methane with chlorine ( 9 A ) a t 315' C. in a tube packed with fuller's earth formed 46% CzCl.,, 45% CCl,, and 9% CsCl6 and C2C16. The conversion based on chlorine was 67%. A novel chlorination apparatus ( 1 A )has been described in which both light and heat are obtained for reaction purposes from an external reaction of hydrogen and chlorine that is conducted in a concentric tube inside the reaction tube. I n this manner, methane gave both CCla and CHC13 together with the bpproduct hydrogen chloride. Chlorination of ethane ( I l A ) at 400" C. and a contact time of 0.19 second gave the following results: C2HsC1, 4%; C2H6C1, 60.2%; CHClzCHI, 29.2%; CHzClCH2C1, 6.401,; and CHCll-
