3,535,391 United States Patent Office Patented Oct. 20, 1970 1. 2 the benzyl chloride is frequently used in industrial applica 3,535,391 STABILIZING COMPOSTIONS tions in a water free condition, it was necessary for the Glendon D. Kyker, Chattanooga, Tenn., assignor to user to separate the benzyl chloride from the water or Weisicol Chemical Corporation, Chattanooga, Tenn., a alkali solution. For a customer desiring benzyl chloride corporation of Tennessee free of water, anhydrous benzyl chloride has sometimes No Drawing. Continuation-in-part of application Ser. No. been stored and shipped in more expensive containers of 591,445, Nov. 2, 1966. This application Apr. 7, 1969, glass or silver, such materials being devoid of catalytic Ser. No. 814,518 activity. The portion of the term of the patent subsequent to The use of strong acids has also been proposed as Jan. 9, 1985, has been disclaimed O stabilizers for aralkyl halides. However, these acids often Int. CI. C07c 25/00, 25/14 cause corrosion of the containers and tend to deteriorate U.S. C. 260-651 10 Claims the aralkyl halides at high temperatures. In addition to condensation with itself, aralkyl halides ABSTRACT OF THE DISCLOSURE often form condensation products with relatively stable 5 hydrocarbons, particularly in Friedel-Crafts condensa New stabilized aralkyl halide compositions. tions catalyzed by metal contaminates. This reaction is undesirable in the case of aralkyl halides where they are stored or treated in solution with aromatic hydrocarbons. This application is a continuation in part of my copend The aromatic hydrocarbons may be inherently present as a ing application Ser. No. 591,445 filed Nov. 2, 1966 and result of the preparation of the aralkyl halides. For ex now abandoned. ample, in the preparation of benzyl chloride from toluene, This invention relates to the stabilization of aralkyl some of the starting material may be retained in solution halides. More particularly, this invention relates to com in the final product. Other aromatic hydrocarbons which positions and a process for preventing the deterioration may be present and may serve as a co-reactant are ben of aralkyl halides through Friedel-Crafts reactions cata Zene, Xylene, and the like, as well as their halo- and lyzed by metal contamination. alkylhalo-substituted compounds. Aralkyl halides deteriorate in storage and handling Thus, there is a present need for a process of stabiliz due to the effects of various conditions encountered there ing aralkyl halides and for stabilized aralkyl halide com in. The principal cause of instability of the aralkyl halides positions not requiring water, aqueous solutions, strong is contamination with various metals. This contamina 30 ly alkaline materials or strong acids. Such process and tion catalyzes Friedel–Crafts type condensations result compositions would permit aralkyl halides to be shipped ing in lowered purity and in some cases complete resini and stored in metallic containers without harmful de fication. The contamination may be due to the presence of gradation of the halide or damage to the container. the metals themselves, such as iron, nickel, copper, tin, Therefore it is one object of the present invention to aluminum, antimony, boron, cadmium, manganese, 3 5 provide stabilized aralkyl halide compositions. titanium, tungsten and zinc, or to the presence of salts or It is another object of the present invention to pro other compounds of the metals. vide a process for stabilizing aralkyl halides during prep The degree of instability of the aralkyl halides varies aration, purification, storage and use. considerably depending on such factors as the degree Still another object of the present invention is to pro of initial purity, the nature of the container and the 40 vide aralkyl halide compositions which are resistant to conditions under which the aralkyl halide has been proc Friedel-Crafts condensations and polymerization catalyzed essed, purified and stored. This lack of stability is a serious by metal contamination. problem which results in loss of the compounds them These and other objects and advantages of the present selves and frequently damages to the containers and stor invention will be readily apparent from the ensuing de age tanks. Among the halides the chlorides in particular scription and examples. tend to decompose under normally encountered storage The stabilizing aralkyl halide compositions of the pres conditions and are not considered safe for transporting ent invention comprise an aralkyl halide and a compound as industrial chemicals in iron drums. The instability prob of the formula lem of these compounds is distinct from the instability R problem encountered with the alkyl halides such as car bon tetrachloride where the instability is largely brought / about by contamination with moisture. To correct this R3 (I) type of instability, dehydrating agents have been utilized, wherein M is selected from the group consisting of phos especially anhydrous salts which react with the water to phorus, arsenic, PFO, ASRO, form stable hydrates. In contrast the present instability problem exists even in the absence of water. X X Of particular commercial importance is benzyl chlo P. and As ride. Benzyl chloride is normally prepared by the chlori R4 R4 nation of toluene leading to a product having therein X is selected from the group consisting of chlorine, bro a proportion of benzal chloride and benzotrichloride along 60 mine and iodine; R4 is selected from the group consisting with the benzyl chloride. This commercial product tends of chlorine, bromine, iodine and Z; and Z, R1, R and R. to undergo undesirable condensation or decomposition, or are independently selected from the group consisting of both, in storage and it oftentimes develops a dark color. alkyl and haloalkyl containing from one to ten carbon These objectionable reactions may occur not only during the storage and handling but also during the separation and atoms and purification of benzyl chloride or other desired product from the mixture of compounds obtained in the chlorina tion of toluene. Heretofore when benzyl chloride has been shipped in Yin iron drums, an aqueous solution of an alkali such as so 70 wherein n is an integer from 0 to 1, R5 is an alkylene group dium carbonate has been mixed with the benzyl chlo containing from one to ten carbon atoms; Y is selected ride to prevent the above mentioned deterioration. Since from the group consisting of chlorine, bromine and alkyl 3,535,391 3. 4. and haloalkyl containing from one to ten carbon atoms, tion have the formula wherein R' and R'' are independ and n is an integer from 0 to 5. ently selected from the group consisting of hydrogen, chlo The process of the present invention comprises adding rine and bromine, and R is independently selected from to the araykyl halide to be stabilized against Friedel the group consisting of chlorine, bromine, iodine, alkyl Crafts reaction catalyzed by metal contamination, an of up to six carbon atoms and chloroalkyl of up to six effective stabilizing annount of a compound of structural carbon atoms. Formula I. Preferably, an effective amount of the com The aralkyl halides ar exemplified by the group con pound described in the paragraph following structural sisting of Formula I is utilized. benzyl chloride The compounds of Formula I which are useful to stabi 10 2-chlorobenzylchloride lize aralkyl halides in the composition and process of the 4-chlorobenzylchloride present invention are exemplified by: trimethylphosphine, 2,4-dichlorobenzylchloride trimethylphosphine oxide, trimethylphosphine dichloride, 2,5-dichlorobenzylchloride trimethylphosphine dibromide, trimethylphosphine di 2,6-dichlorobenzylchloride iodine, tetramethylphosphonium chloride, trimethylarsine, 2,4,6-trichlorobenzylchloride trimethylarsine oxide, tetramethylarsonium iodide, ethyl 2,3,6-trichlorobenzylchloride dimethylphosphine, diethylmethylarsine, diethylmethyl 3,4,5-trichlorobenzylchloride phosphine, ethyldimethylarsonium iodide, triethylarsine 2,3,4,5-tetrachlorobenzylchloride oxide, triethylphosphine, triethylarsine, triethylphosphine 2,3,4,6-tetrachlorobenzylchloride oxide, butyldimethylphosphine, butyldimethylarsine, butyl 20 2,3,5,6-tetrachlorobenzylchloride dimethylphosphine oxide, trioctylphosphine, trioctylphos pentachlorobenzylchloride phine dichloride, trioctylphosphine oxide, (trifluoro o-methylbenzylchloride methyl) dimethylphosphine, (trifluoromethyl) dimethyl p-methylbenzylchloride arsine, tris(trifluoromethyl) phosphine, tris(trifluoro 2,3-dimethylbenzylchloride methyl) arsine, triphenylphosphine, triphenylarsine, tri 3,4-dihexylbenzylchloride phenylphosphine oxide, triphenylphosphine dichloride, 2,5-dipropylbenzylchloride benzyltriphenylphosphonium chloride, methyltriphenyl 2,4,5-tributylbenzylchloride phosphonium chloride, diphenyltolylphosphine oxide, di 2,4,6-tripentylbenzylchloride phenyltolylarsine, benzyldiphenylphosphine oxide, benzyl 2,3,4,6-tetramethylbenzylchloride diphenylphosphine, dibenzylphenylphosphine, dibenzyl 2,3,5,6-tetraethylbenzylchloride phynylphosphine oxide, phenyldi-p-tolylarsine dichloride, 2,3,4,5-tetramethylbenzylchloride tri-p-tolylarsine, tri-p-tolylphosphine, tri-p-tolylphosphine benzal chloride oxide, (o-chlorophenyl) diphenylarsine, (o-bromophenyl) o-methylbenzalchloride diphenylphosphine, (o-chlorophenyl) diphenylphosphine, p-methylbenzalchloride tris(p-chlorophenyl) phosphine oxide, (p-bromophenyl)- 3. 5 m-methylbenzalchloride phenyl-p-tolylarsine, (dibromomethyl) triphenylphos 2-chlorobenzalchloride phonium bromide, (p-ethylphenyl)-phenyl-p-tolylarsine, 4-chlorobenzalchloride and the like. 2,3-dichlorobenzalchloride The compounds of the Formula I are utilized in the 3,4-dichlorobenzalchloride process and composition of the present invention, prefer 40 2,4,6-trichlorobenzalchloride ably in an amount effective to stabilize the aralkyl halide 2,3,6-trichlorobenzalchloride against Friedel-Crafts reactions catalyzed by metal con 3,4,5-trichlorobenzalchloride tamination. It is preferred to add from about 0.0005% 2,3,4,5-tetrachlorozenzalchloride to about 1% and more preferably to add from about 2,3,4,6-tetrachlorozenzalchloride 0.0005% to about 0.1% of said compound for each part 2,3,5,6-tetrachlorobenzalchloride per million of metal contamination encountered. Gener pentachlorobenzalchloride ally the addition of from about 0.0001% to about 0.1% of benzotrichloride a compound of the Formula I based on the weight of 2-chlorobenzotrichloride aralkyl halide to be stabilized will be sufficient to provide 4-chlorobenzotrichloride stabilization under ordinary conditions of storage and 2,5-dichlorobenzotrichloride handling. 3,4-dichlorobenzotrichloride The aralkyl halides with which the process of the 2,4,5-trichlorobenzotrichloride present invention is particularly useful are those of the 2,3,4-trichlorobenzotrichloride formula 2,3,4,5-tetrachlorobenzotrichloride o, ox-dichloro-a-bromotoluene 5 5 o,c-dibromo-o-chlorotoluene o-chloro-o-bromotoluene o-bromobenzylchloride NX p-bromobenzylchloride Hcs-p) 2,5-dibromobenzylchloride wherein A is chlorine or bromine; R and R' are inde 60 2,4-dibromobenzylchloride pendently selected from the group consisting of hydrogen, 2,4,5-tribromozbenzylchloride chlorine, bromine, alkyl of up to six carbon atoms, chloro o-bromobenzalchloride alkyl of up to six carbon atoms, bromoalkyl of up to six p-bromobenzalchloride carbon atoms, aryl of up to 12 carbon atoms, alkyl phenyl 2,3-dibromobenzalchloride of up to nine carbon atoms, chlorophenyl and bromophen 2,4,5-tribromobenzylchloride yl containing up to five halogen atoms and R is independ o-bromobenzotrichloride ently selected from the group consisting of chlorine, bro p-bromobenzotrichloride mine, iodine, alkyl of up to six carbon atoms, chloroalkyl 2,5-dibromobenzotrichloride of up to six carbon atoms, bromoalkyl of up to six carbon 2,4-dibromobenzotrichloride atoms, aryl of up to 12 carbon atoms, alkylphenyl of up 2,4,5-tribromobenzotrichloride to nine carbon atoms and chlorophenyl and bromophenyl o-iodobenzylchloride containing up to five halogen atoms and p is an integer p-iodobenzylchloride from 0 to 5. 2,5-diiodobenzylchloride Preferably the aralkyl halides used in the present inven 75 2,4-diiodobenzylchloride 3,535,391 5 6 2,4,5-triiodobenzylchloride Crafts condensations of aralkyl halides with themselves o-iodobenzalchloride and with aromatic hydrocarbons. p-iodobenzalchloride The compositions and process of the present inven 2,5-diiodobenzalchloride tion for stabilizing arakyl halides will be more clearly 2,3-diiodobenzalchloride understood from the following examples which are pre 2,4,5-triiodobenzalchloride Sented by way of illustration and are not intended to o-iodobenzotrichloride limit the scope of this invention. In the examples, all p-iodobenzotrichloride percentages of materials are by weight based on the 2,4-diiodobenzotrichloride Weight of arakyl halide employed, unless indicated 2,3-diiodobenzotrichloride O otherwise. 2,4,5-triiodobenzotrichloride EXAMPLE 1. 2,4-bis(chloromethyl)toluene 2,5-bis(chloromethyl)toluene Comparative effectiveness of several 3,6-bis(chloroethyl)toluene materials 2,6-bis(chlorobutyl)toluene Benzyl chloride (2 moles) was heated at reflux for 3,4-bis(chloropropyl)-o-xylene 6 hours with m-xylene (4 moles) and ferric chloride 3,5-bis(chloropentyl)-o-xylene (0.1%). The above reaction was repeated in the presence 2,4-bis(chlorohexyl)-mi-xylene of each of the following substances: 2,5-bis(bromomethyl)-mi-xylene Percent 4,5-bis(bromoethyl)-m-xylene 20 Triphenyl phosphine ------0.5 2,3-bis(bromopropyl)-p-xylene Triphenyl amine ------0.5 2,6-bis(bromopentyl)-p-xylene Triphenyl phospate ------0.5 1,3-bis(bromohexyl)-2,4,5-trimethylbenzene Trieresyl phosphate ------0.5 1,2-bis(m-chlorophenyl)-3,5,6-trimethylbenzene 1,4-bis(o-bromophenyl)-2,3,5,6-tetramethylbenzene The progress of the undesired Friedel-Crafts reactions, 1,3-bis(3,4-dichlorophenyl)-2,4,5,6-tetramethylbenzene 25 if any, were measured by weighing the hydrogen 2-chloromethylbenzalchloride chloride evolved. The effectiveness of the various sub 2-chlorohexylbenzotrichloride stances in inhibiting the Friedel–Crafts reactions are 3-phenylbenzalchloride shown in the table below. Only triphenyl phosphine of 3-(4-methylphenyl)benzotrichloride the materials tested effectively inhibited the undesirable 4-propylphenylbenzalchloride 30 Friedel-Crafts reactions. 4-ethylphenylbenzotrichloride benzylbromide TABLE 2-chlorobenzylbromide Percent 4-chlorobenzylbromide of benzyl 2,4-diodobenzylbromide chloride 2,5-dichlorobenzylbromide Stabilizer Time, hrs. reacted 2,4,6-triiodobenzylbromide Triphenylphosphine------6 O 2,4,5-tribromobenzybromide Triphenyl amine- 6 93 Triphenylphosphate- 6 91. 2,3,4-(5-ethylphenyl)benzylbromide 40 Tricresyl phosphate-- 6 88

2,3,4,5-tetrachlorobenzylbromide None------12 99 2,3,4,6-tetrachlorobenzybromide pentachlobenzylbomide benzalbromide EXAMPLE 2. 2-chlorobenzalbromide 4-chlorobenzalbromide Stabilization during distillation 2,4-dichlorobenzalbromide Benzyl chloride (252 g.) containing 0.1% ferric 2,5-dichlorobenzalbromide chloride (0.25 g.) was treated with 0.5% triphenyl 2,4,5-trichlorobenzalbromide phosphine (1.25 g.) and distilled through a 2-foot glass 2,3,4-trichlorobenzalbromide 50 column at 13 mm. Hg pressure during which the tem 2,3,5-trichlorobenzalbromide perature in the pot rose from 65° C. to 190° C. while 2,3,4,5-tetrachlorobenzalbromide the overhead vapor temperature remained constant at benzotribromide 65-67 C. The residual oil was light in color and had 2-chlorobenzotribromide no hydrogen chloride odor indicating that Fridel-Crafts 4-chlorobenzotribromide condensation had not taken place. 2,4-dichlorobenzotribromide 55 2,5-dichlorobenzotribromide EXAMPLE 3 2,3-dichlorobenzotribromide 3,4-dichlorobenzotribromide Stablization during chlorination 2,4,5-trichlorobenzotribromide Benzyl chloride (506 g.) treated with 0.1% anhydrous 2,3,4-trichlorobenzotribromide 60 ferric chloride and 0.5% triphenyl phosphine gave a clear 2,3,5-trichlorobenzotribromide yellow liquid solution. Chlorine gas was bubbled through 2,3,4,5-tetrachlorobenzotribromide the liquid solution at 50–60 C. for 6/2 hours. Only a o-methylbenzylbromide negligible trace of hydrogen chloride gas evolved during p-methylbenzylbromide the chlorination indicating that there was little or no : 2,3-dimethylbenzylbromide 65 tendency for polymerization of benzyl chloride. Without 3,4-dimethylbenzylbromide the triphenyl phosphine extensive polymerization occurs 2,5-dimethylbenzylbromide 2,4,5-trimethylbenzylbromide during chlorination. 2,4,6-trimethylbenzylbromide EXAMPLE 4 2,3,4,6-tetramethylbenzylbromide 70 Stabilization against polymerization 2,3,5,6-tetramethylbenzylbromide catalyzed by various metals pentamethylbenzylbromide Separate portions of benzyl chloride (12.65 g.) were The compositions and process of the present invention treated with one of the following compounds in an successfully retard and often completely prevent Friedel 75 amount equal to 4650 p.p.m. of metal in benzyl 3,535,391 7 8 chloride. This latter quantity refers to the amount of From the foregoing description of the invention it metal whether it was added as free metal or metal halide. will be understood by those skilled in the art that minor nickel metal (in form of nickel wool) alterations and modifications may be made therein. It nickel chloride is intended, therefore that the appended claims include stannic chloride 5 all such modifications and alterations as may fall within Zinc chloride the true spirit and scope of the invention. I claim: One portion treated with each metal was further treated 1. A stabilized aralkyl halide composition comprising with triphenyl phosphine (1.5 miles per mole of metal). an aralkyl halide of the formula All of the portions were heated to 145-155° C. for 15 minutes. In the portions without triphenyl phosphine O R hydrogen chloride gas evolved indicating condensation -C-A and polymerization was taking place. In the portions in R -- ly cluding triphenyl phosphine no evolution of hydrogen chloride gas was observed and the odor of the gas was II (5-p) not detected. The latter indicated that the benzyl chloride wherein A is chlorine or bromine; R' and R'' are inde was effectively stabilized with triphenyl phosphine endently selected from the group consisting of hydrogen, against reactions catalyzed by all of the metals tested. chlorine, bromine, and R is independently selected from EXAMPLE 5 the group consisting of chlorine, bromine, alkyl of up 20 to six carbon atoms, chloroalkyl of up to six carbon Stabilization with several stabilizers atoms, bromoalkyl of up to six carbon atoms, aryl of Benzyl chloride (12.65 g.) was contaminated with 5 up to 12 carbon atoms, alkyl phenyl of up to nine car p.p.m. ferric chloride. This solution was divided in 4 bon atoms and p is an integer from 0 to 5; and an effec equal portions and to each of 3 of the portions was added tive stabilizing amount of a compound of the formula one of the following in an amount equal to 0.1% by weight: triphenyl phosphine, trioctyl phosphine oxide, and tributyl phosphine. All four portions were heated at 150 170° C. for 15 minutes. The portion which was not stabilized turned dark immediately and evolved hydrogen wherein M is selected from the group consisting of phos chloride gas throughout the heating procedure; whereas 30 phorus, arsenic, PFO, the 3 treated portions remained clear and did not evolve X any gases during the heating procedure. / 1. P and As EXAMPLE 6 N N R R Stabilization of benzotrichloride X is chlorine, bromine or iodine; R is selected from Benzotrichloride (195.5 g.) was contaminated with the group consisting of chlorine, bromine, iodine, and Z; 0.1% anhydrous ferric chloride and treated with triphenyl R1, R2, R are independently selected from the group arsine (1.1 mols per mole of ferric chloride). A portion consisting of alkyl and haloalkyl containing from one to without triphenyl arsine was used as a control. The two 40 ten carbon atoms and solutions were heated to 210-218 C. and the rate of hydrogen chloride gas evolved was measured and calcu lated as a mole ratio as indicated in the table below. (IRs) in N The solution treated with triphenyl arsine was effectively Yin stabilized against Friedel-Crafts condensation. Z is selected from the group consisting of alkyl contain TABLE ing from 1 to 10 carbon atoms and eating time, Stabilizer hrs. Molcratio 50

Triplienyl arsine 0.0 O 0.25 0.0137 0.50 0.123 0.0 0.232 wherein n is an integer from 0 to 1, Rs is an alkylene 0.25 0.41 group containing from one to ten carbon atoms; Y is 0.50 O. 452 Selected from the group consisting of chlorine, bromine 1 Hydrogen chloride? benzotrichloride. 5 5 and alkyl containing from one to ten carbon atoms, and m is an integer from 0 to 5. EXAMPLE 7 2. The composition of claim 1 wherein R' and R' are Stabilization of benzal chloride independently selected from the group consisting of hy drogen, chlorine and bromine, and R is independently se Benzal chloride (2 moles) was treated with anhydrous 60 lected from the group consisting of chlorine, bromine, ferric chloride (0.1%). One-half of this solution was alkyl of up to six carbon atoms and chloroalkyl of up treated with triphenyl phosphine (0.3 g.; 1.15 moles per to six carbon atoms. mole ferric chloride). Both portions of the solution were 3. The composition of claim 1 wherein the aralkyl heated to reflux. The portion treated with triphenyl phos halide is selected from the group consisting of benzyl phine was yellow at the reflux temperature and no hydro chloride, benzal chloride and benzotrichloride. gen chloride gas was detected. The untreated solution 4. The composition of claim 1 wherein the aralkyl began to release hydrogen chloride gas at 25 C., was halide is benzyl chloride. black at the reflux temperature and released 0.082 mole 5. The composition of claim 1 wherein the aralkyl of hydrogen chloride per mole of benzal chloride. At halide is benzal chloride. the end of one hour of heating the treated solution had 70 6. The composition of claim 1 wherein the aralkyl not evolved any hydrogen chloride and was lighter in halide is benzotrichloride. color than the untreated solution while the untreated 7. The composition of claim 1 wherein the stabilizing solution had evolved 0.178 mole of hydrogen chloride compound is triphenyl phosphine. per mole of benzal chloride, indicating undesirable Frie 8. The composition of claim 3 wherein the stabilizing del-Crafts reactions had taken place. 5 compound is triphenyl phosphine. 3,535,391 9 10 9. The composition of claim 1 wherein the stabilizing 3,112,348 11/1963 Campbell ------260-652.5 compound is triphenyl arsine. 8 3,363,013 1/1968 Kyker ------260-651 10. The composition of claim 3 wherein the stabilizing . FOREIGN PATENTS compound is triphenyl arsine. 615, 186 2/1961 Canada. References Cited ) HOWARD T. MARS, Pri Exami UNITED STATES PATENTS g , Frimary Examiner 2,803,663 8/1957 Kohn ------260-652.5 XR U.S. C. X.R. 2,970,113 1/1961 Bachtel ------260-6525 XR 260-649 2,994,653 8/1961 Miller. IO