Patented May 16, 1939 2,158,519

UNITED STATES PATENT OFFICE 2,158,519 PRODUCTION OF AROMATIC ALDEHYDES Walter Christian Meuly, New Brunswick, N. J., assignor to E. I. du Pont de Nemours & Com pany, Wilmington, Del, a corporation of Del aWare No Drawing. Application April 20, 1938, Serial No. 203,131 1 Claims. (CI, 260-599) This invention relates to the production of aro benzenes. By varying the conditions of Gatter matic aldehydes, the present application being a mann, for instance, by working in a closed vessel continuation-in-part of my copending applica at extremely high pressures (800 atmospheres), tion Serial No. 112,710, filed November 25, 1936. I have succeeded in stepping up the yield to as More particularly, this invention relates to the high as 18%, but this is still far too low to make 5 5 production of para-alkyl aldehydes of the gen the process practical from the commercial View point. eral formula, That my experiences above have been shared by others is evident from the fact that although cuminic aldehyde is a valuable perfume interme- 0 wherein R is an alkyl radical containing from 1. diate, and therefore in industrial demand, the to 8 carbon atoms, or more. literature is replete with proposed alternative It is an object of this invention to provide a processes for manufacturing this Valuable COIn novel and efficient method for preparing alde pound without making use of the direct intro 5 hydes of the above general formula. It is a fur duction of the carbonyl group by means of carbon 5 ther object of this invention to provide a method monoxide, for the manufacture of para-alkylated aromatic The major difficulty with the Gattermann aldehydes which enables one to start with cheap synthesis, when applied to alkylated benzenes initial materials. Other and further important containing an alkyl group with more than One objects of this invention will appear as the de carbon atom, resides in the fact that under the 20 20 scription proceeds. conditions of the Gattermann reaction the alkyl Para-alkyl benzaldehydes have been previ group migrates or is split off completely. As a Ously prepared by applying the Gattermann-Koch result, most of the reactants are wasted in the aldehyde synthesis to alkyl benzols. This Syn production of di- and polyalkylated benzenes and thesis may be considered as a Special case of the di- and polyalkylated benzaldehydes with forma 2 5 2 5 Friedel-Crafts synthesis, and consists of reacting tion of large amounts of benzene. This splitting together a suitable homolog of benzene with car reaction is not prevented by the addition of ben bon monoxide gas and dry hydrochloric acid in zene as a diluent as has been suggested by the presence of anhydrous aluminum chloride: Gattermann. Al2Cl6 It has also been known that benzene itself 30 30 CE --CO--HC-CH3- -CIO--HC (that is, without an alkyl substituent) does not react under the influence of aluminum chloride (Annalen 347, 347; 1906; Berichte, 30, 1622; 1897). with carbon monoxide and hydrochloric acid to This reaction gives a good yield (73%) of p-toluic produce benzaldehyde. This fact was noted by aldehyde based on the quantity of toluene Con Gattermann, Who States: sumed. It requires, however, a large excess of "The reaction is completely unsuccessful with CO gas, since only about 30% of the CO gas benzol under the influence of aluminum Chlo passed through the reaction mass combines with ride. This behavior is very desirable because the toluene. it is thus possible to use benzol as a diluent 40 40 Moreover, in the case of the higher homologs with such hydrocarbons as are sensitive to of benzene the situation is much less favorable. Although Gattermann speaks of "good yields' aluminum chloride'. (Annalen, 347, 347). in conjunction with the aldehydes derived from I have now found that benzene may be very ethyl-benzol and isopropyl-benzol, I have been readily and efficiently converted into cuminic al unable to substantiate these claims in my re dehyde or any other optional para-alkyl benzal 45 45 searches. More particularly, I have run a Series dehyde, by subjecting it simultaneously to the of experiments with this reaction as applied to action of carbon monoxide, anhydrous aluminum isopropyl-benzene, and followed very carefully chloride and isopropyl chloride or any agent the directions given in the Gattermann reaction. capable of introducing the desired alkyl group. 50 The yield of cuminic aldehyde (p-isopropyl-benz The choice of alkylating agent Will of course 50 aldehyde), however, was very low, being about depend on the nature of the desired alkyl group 14% of theory based on the quantity of isopro in para, position to the aldehyde group, but aside pyl-benzene consumed. On the other hand over from this consideration may be any compound 50% of the isopropyl-benzene was recovered in Which is capable of introducing said alkyl group 55 the form of benzene and of di- and poly-isopropyl into benzene under the influence of aluminum 55 2 2,158,519 chloride while simultaneously liberating hydrogen The recovered alkyl benzols may be reused in the chloride. This one may employ alkyl halides, next operation with the benzol. alkyl alcohols, alkyl ethers, alkyl borates, or alkyl esters of organic acids (formates, acetates). EXAMPLE 2 The test is here whether or not a given compound By feeding at Ordinary temperature simultane is capable of condensing With ben Zeine under the ously carbon monoxide and tertiary-butyl chloride influence of aluminum chloride (that is, in the into a mixture of benzol, aluminum chloride and absence of CO) to give an alkyl benzol of the cuprous chloride, p-tertiary-butyl-benzaldehyde desired type. If it is capable, it is suitable for is formed, which may be separated from the re 0 my novel reaction. action mass by means of its bisulphite compound. In my parent application above referred to I In the pure state, it is a colorless oil; Boiling point have indicated as desirable to add hydrogen at 3.5 mm. of Hg: 91 to 92° C. chloride to the reaction mass, this reactant being ExAMPLE 3 fed into the reaction mixture in the form of a dry 5 gas. The present application is concerned pri From benzol, carbon monoxide and technical . marily with a mode of carrying out my general amyl chloride is obtained in a Similar manner invention wherein no positive addition of HCl is as described in Example 2, p-tertiary amyl benzal practiced. I find that the latter step is not es dehyde, characterized by the following constants: sential to my invention, inasmuch as the reac boiling point at 5 mm. Hg: 122 to 124° C.; re 20 tion generally proceeds quite satisfactorily with fractive index n20: 1.5270; melting point of semi- i. out it. I presume that the explanation of this carbazone: 199 to 200° C.; odor: Spicy-sweet and resides in the fact that alkyl halides, alcohols, very lasting. alkyl ethers and certain alkyl esters develop HCI EXAMPLE 4 during the course of the reaction. From cyclo-hexyl-chloride, carbon monoxide 25 But regardless What the exact explanation of and benzol is obtained, in a manner similar to '.. the phenomenon is, it is clear that my present Example 2, p-cyclohexyl-benzaldehyde; boiling invention constitutes a further improvement on point at 2.5 mm. Hg:126° C. the process of producing aromatic aldehydes of the type herein above discussed, inasmuch as it EXAMPLE 5 30 economizes both on materials and labor. From m-methyl-cyclohexyl-chloride, carbon 3) My present improvement is applicable with any Inonoxide and benzol is obtained, in an analogous alkylating agent which is capable of developing manner, p- (m-methyl-cyclohexyl)-benzaldehyde. HCl in Friedel-Crafts synthesis. This group of In the pure State it is a colorless viscous oil. alkylating agents includes alkyl halides and sub Boiling point at 1.5 mm. Hg: 110° C.; refractive 35 stances which by reaction with anhydrous alumi index 1120: 1.5490; melting point of semi-carba num chloride produce alkyl chlorides in situ, as Zone: 215 to 217° C.; possessing an intense and illustrated by the following equation using an lasting odor of the citrus type. alkyl ether as an example: EXAMPLE 6 (1) 40 Use of an alcohol as alkylating agent ROR-AlCl3->2RC1--AlOCI Into a mixture of 480 parts of benzol, 400 parts (2) of AlCl3 and 32 parts of Cu2Cl2 are introduced Simultaneously over six hours at Ordinary tem More specifically, the group of alkylating agents perature 42 parts of carbon monoxide and 90 applicable with my present invention comprises: parts of isopropanol. The cuminic aldehyde : formed may be isolated from the reaction product Alkyl halides, for instance alkyl chloride, or by means of its bisulphite compound. bromides; Alcohols; EXAMPLE 7 50 Dialkyl ethers; USe of an ether as alkylating agent Alkyl esters of weak acids, for instance borates, formates or acetates. Into a mixture of 800 parts of benzol, 650 parts of AlCl3 and 60 parts of Cu2Cl2 are added over Without limiting my invention to any particular Several hours simultaneously at 20 to 40° C. 120 55 procedure, the following examples are given to parts of carbon monoxide and 204 parts of di illustrate my preferred mode of operation. Parts isopropyl ether. Cuminic aldehyde in good yield . mentioned are by weight. may be isolated from the reaction mass by frac EXAMPLE 1. tional distillation or preferably by treatment With Sodium bisulphite solution. 700 parts of benzol, 650 parts of aluminum 60 chloride and 70 parts of cuprous chloride are EXAMPLE 8 f) placed into a vessel provided with agitation. At If in Example 7, the 204 parts of di-isopropy 25 to 30° C. are gradually introduced during ether are replaced by 300 parts of dicyclohexyl five hours, at ordinary pressure, 240 parts of iso ether, the reaction product is para-cyclohexyl 65 propyl chloride and 112 parts of carbon monoxide benzaldehyde. gas. The gas is bubbled through the reaction EXAMPLE 9 mass and may be collected after passage for re 500 parts of benzol, 400 parts of aluminum use in a future operation. chloride and 40 parts of cuprous chloride are The reaction maSS is poured on ice and sepa placed into a vessel provided with agitation. 200 70 rated into its components by suitable methods parts of tri-isobutyl borate and 100 parts of car Such as fractional distillation or fractional bi bOn monoxide gas are then simultaneously fed Sulphitation. Besides unreacted benzol, there in over a period of 4 hours, under ordinary pres are obtained 115 parts of pure cuminic aldehyde, Sure and at a temperature of about 40° C. Fron 40 parts of di-isopropyl benzaldehyde, 80 parts of the reaction product, para-tertiary-butyl-benz 5 isopropyl benzol, and some di-isopropyl benzol. aldehyde is obtained in good yield. 5 2,158,519 3 It Will be understood that my invention is not ination of the isolation and purification of the liiinited to the precise details given in the above alkyl benzol, but the yield of aldehyde is also examples, but may vary widely within the spirit much improved, which constitutes a further im of this invention. Thus, the reaction is opera portant economic advantage. 5 tive at ordinary pressure from 0° C. to the tem Also, in my improved process no hydrogen 5 perature of boiling benzol (78° C.); although for chloride needs to be fed in, which is a consider best results, the range of 10 to 50° C. is pre able Saving in cost of materials and manipula ferred. Under pressure, the temperature may be tion. In my novel process the reaction of alkyla increased above 78° C. tion and that of carbonylation not only run side O In the above examples, pressures from 1 to 2 by side without interfering with each other, but 0 atmospheres, absolute, have been employed. they cooperate with each other in several im There is, however, no limitation to the pressure portant respects to produce novel and unex eimployed except for the fact that at very high pected effects. Thus the reaction of alkylation preSSures there may occur formation of benz seems to furnish the HCl requisite for the car aldehyde Simultaneously with the formation of bonylation. The two reactions further cooper 5 &ilkyl benzaldehyde. ate, in Some unexplainable manner, to increase The relative quantities of reagents employed in most cases the yield of the desired main re may vary Within wide limits. To assure good action product, and to extend the carbonylation yields, the amount of benzol should be at least reaction to fields where it has hitherto been a 20 twice the theoretical amount (two mois benzol practical failure, as is typified by the case of 20 for 1 mol carbon monoxide), but it may be much benzol above discussed. more or less. As for the alkylating agent, best Moreover, my novel process has enabled me to yields are obtained if the same and carbon mon synthesize certain novel aldehydes. Thus, among Oxide are used in about molecular proportions. the compounds Synthesized in the above exam 25 If the amount of alkylating agent is increased, ples the following appear to be novel compounds: 25 the main reaction product may be the corre p-tertiary-amyl benzaldehyde (Example 3) and Sponding dialkyl benzaldehyde. The amount of p- (m-methyl-cyclohexyl)-benzaldehyde (Exam AlCl3 may vary greatly but for best yield it should ple 5). These are useful as perfume materials be used in at least one molecular proportion for due to their original and lasting odors. 30 each molecular proportion of carbon monoxide. I claim: 30 The function of the cuprous chloride is cata 1. The process of preparing a para-alkylbenz lytic. Its amount, therefore, may vary widely, aldehyde which comprises reacting upon ben Say from 2 to 20% by Weight of the aluminum Zene with an alkylating agent in the presence of chloride. It may be replaced by other equiva aluminum chloride, and further reacting upon 35 lent catalysts, for instance, cuprous bromide. the same reaction mass with carbon monoxide, 35 The preferred method of mixing the materials Without isolating any intermediate compounds. consists of adding simultaneously the alkylating 2. The process of preparing a para-alkyl agent and the carbon monoxide to a mixture of benzaldehyde, which comprises reacting upon the benzol, aluminum chloride and catalyst. benzene simultaneously With carbon monoxide 40 i3owever, it is possible to add the alkylating and with an agent adapted to introduce an alkyl 40 agent first. group, in the presence of aluminum chloride. A number of modifications have been pro 3. A process as in claim 1 wherein the alkyl posed for the Gattermann aldehyde synthesis, ating agent is selected from the group consist all of Which may be used in connection with the ing of alkyl halides and compounds which are present proceSS. For instance, nitrobenzol or capable of yielding an alkyl halide by reaction 45 Ortho-nitro-toluol may be added as solvents. with aluminum chloride. Iron chloride or titanium chloride may be pres 4. A process as in claim 2 wherein the agent eit in the AlCl3 or may be added to it. adapted to introduce an alkyl group is Selected Among the alkylating agents, this invention is from that group of alkylating agents which are prinarily concerned with Such as will introduce adapted to liberate hydrogen chloride in Situ in In ore than one carbon atom. a Friedel-Craft reaction. The advantages of my invention will now be 5. The process of preparing a para-mono readily understood. alkyl benzaldehyde, which comprises reacting By the novel method of this invention, it be upon benzene with carbon monoxide in the pres 5 s coines possible to extend the Scope of the Gat ence of aluminum chloride, while simultaneously 55 termann reaction for the introduction of car feeding into the same maSS a compound adapted bon monoxide into the benzol ring. The Gat to condense With benzene under the influence of termann reaction has heretofore been used suc aluminum chloride to give an alkylated benzene cessfully and commercially, only for Such alkyl while simultaneously liberating hydrogen chlo 3 O benzaldehydes as possess side chains of one car ride. 60 bon atom. By the novel process good yields of 6. The process of preparing a para-mono-al any alkyl benzaldehydes may be obtained. kyl-benzaldehyde, which comprises feeding simul The Gattermann reaction starts from alkyl taneously into a mixture of benzene, aluminum beinzols, which are expensive to prepare in all chloride and a Gattermann-Synthesis catalyst, 5 cases where the alkyl group contains two or 65 more carbon atoms. The novel process starts gaseous carbon monoxide and an alkyl derivative ifrom the inexpensive benzol and inexpensive adapted to act as an alkylating agent under the alkylating agents, such as the alkyl chlorides or influence of aluminum chloride, while simulta alcohols. neously liberating hydrogen chloride. As shown previously, the yields of p-alkylated 7. A process as in claim 6, the catalyst being a 70 aldehydes are much Superior With the novel cuprous halide. in ethod for all cases where the alkyl group con 8. A process as in claim 6, the catalyst being tailins three or more carbon atoms. Thus, not cuprous chloride. Only is the preparation of alkyl-benzol and alkyl 9. A proceSS as in claim 6, the quantity of al ) benzaldehyde condensed into one step with elim kylating agent passed-in being substantially 175 4. 2,158,519 Inol for each 2 mols of benzene, whereby to avoid alcohol, diisopropyl ether, and isopropyl esters formation of dialkylated benzaldehyde. of Weak acids. 10. A process of producing cuminic aldehyde, 11. A process of producing cuminic aldehyde, Which comprises passing simultaneously into a Which comprises passing Simultaneously into a nixture of benzene, aluminum chloride and cu mixture of benzene, aluminum chloride and cu 5 prous chloride, a stream of carbon monoxide gas prous chloride, a Stream of Carbon monoxide gas and an isopropylating agent selected from the and di-isopropyl ether. group consisting of isopropyl halides, isopropyl WALTER, CHRISTAN MEULY.