Preparation of acid halides
United States Patent [191 Doorenbos et al.  
 [451 Apr. 1, 1975 PREPARATION OF ACID HALIDES [75] Inventors: Harold E. Doorenbos, Midland;  
 Darell D. Toner, SanfordgLinda G. Calhoun, Beaverton, all of Mich.  
 [731 Assignee: The Dow Chemical Company,  
 Midland, Mich.  
 [221&#39; Filed: Oct. 17, 1969 [21] Appl. No.: 867,377  
 [52] US. Cl. 260/544 L, 260/544 M, 260/544 Y [51] Int. Cl. C07c 51/58 [58] Field of Search 260/544 M, 544 Y, 544 L,  
 Primary E.\&#39;aminerLorraine A. Weinberger Assistant Examiner-Richard D. Kelly Attorney, Agent, or Fi &#39;rmL. Wayne White ABSTRACT Acid halides are prepared by reacting in the presence of a Lewis acid catalyst (a) sulfur dioxide, and (b) an organic compound bearing one or more allylic acid/or benzylic trihalomethyl groups. By halo is meant fluoro, chloro or bromo. ln example 6 Claims, No Drawings PREPARATION OF ACID HALIDES BACKGROUND OF THE lNVENTlON Acid fluorides, chlorides and bromides are a known class ofcompounds having known utilities. Many methods of preparing such compounds from the corresponding acids or acid salts are known, as illustrated by R. B. Wagner and H. D. Zook, Synthetic Organic Chemistry,&#34; John Wiley &amp; Sons, lnc., N.Y., N.Y. (I953), Chapter 17. Other methods of preparation of aromatic acid halides are illustrated by N. Rabjohn, Journal of the American Chemical Society (.I.A.C.S.), 76. 5479 (1954). and by R. C. Schreyer, J.A.C.S., 80, 3483 (1958), wherein iso-and terephthalyl chloride were prepared from a, a. a, a, a, a-hcxaehlor-m or pxylene.  
 SUMMARY OF THE INVENTION A novel method of preparing acid fluorides, chlorides and bromides has now been discovered which comprises reacting in the presence of a Lewis acid catalyst (a) sulfur dioxide and (b) an organic compound containing at least one allylic and/or benzylic trihalomethyl group, i.e.. a trifluoromethyl, trichloromethyl or tribromomethyl group, or a mixed halomethyl group.  
  The novel process is illustrated by the following reaction equation:  
  LA 9 R(CX so rue-x) n so):  
 wherein X is fluoro, ehloro or bromo; LA is a Lewis acid. and R is an n-valent hydrocarbon or halosubstituted hydrocarbon radical, wherein the carbon atom of attachment is unsaturated and n is an integer from I to about 4, and is preferably 1 or 2.  
  The advantages of preparing acid halides according to the subject process are (a) high product yields of ll, and (b) the production of the reaction by-products. lll,  
 thionyl halides which are themselves useful and desirable products. The thionyl halides are volatile components easily separated and recovered from the reaction mixture by common distillation techniques.  
  Suitable reactants in the process are a known class of compounds which is generically represented by (l) above. Examples of suitable reactants within formula I&#39; are those having l allylic trihalomethyl groups, such as those having the structural formula R R C=C(R;,)CX;,, wherein R,, R and R are hydrogen, X, hydrocarbon groups or halo-substituted hydrocarbon groups having I to about 20 carbon atoms, e.g.. alkyl, aryl, cycloalkyl, alkaryl, aralkyl, etc., and include for example those having the following values for X and and other like compounds, or (2) benzylic trihalomethyl groups, such as those in formula I wherein Table II Z-naphthyl 1,4-naphthylene 1,5-naphthylene 2,6-naphthylene p,p&#39;-biphenyle&#39;ne p,p&#39;-biphenylene oxydi-p-phenylene thiodi-p-phenylene Cl 3 l,3,5-C H Br l l, -l,5,8-C H Cl 2 C Cl H Cl 2 C 01 Cl 2 perchloro-p ,p biphenylene Cl 1 perchlorooxydi-p-phenylene and other like compounds. Preferred reactants are those in formula I wherein X is chloro. and the most preferred reactants are l.l,l-trichloropropene, perchloropropene. l,2-bis(trichloromethyl)ethylene. perchlorobutene-Z, benzotrichloride. a.a,a,a,oz&#39;,a-hexachloro-mor p-xylene, a.a,a.a,a,a-hexachloro-p,pbitolyl, .a,a,a.a&#39;,oz.a-2.5-octachloro-p-xylene. perchloro-p-xylene, perchloro-pp&#39;-bitolyl.  
  Any one or any mixture of the known class of Lewis acids may be included in the&#39;instant reaction as a catalyst. Examples of suitable such catalysts include BF BF .etherate. AlCl; AlBr FeCl FeBr SnCl ZnCland other like compounds. Preferably, the halogen in the catalyst is the same as the X in the trihalomethyl group(s) attached to R. A catalytic amount of Lewis acid catalyst is required in the reaction, such as amounts up to about percent by weight or more based on the weight of R-(-CX reactant. Typically, the preferred amount of catalyst is between 0.01 and 1 percent by weight. same basis.  
  S0 is suitably used in substantially any amount in the reaction. However, the stoichiometry of the reaction requires one mole of SO per -CX group. Hence. at least one mole of $0 per CX group is preferred, and an excess ofSO- is most preferred. This preference is based on the fact that excess S0 acts not only to drive the reaction to completion but also acts as a reaction solvent.  
  Other compounds may be advantageously used as solvents so long as they are inert in the reaction. i.c.. they do not react with any of the reactants or products. Examples of such compounds include carbon tetrachloride. perchloroethylene, and other like halogenated hydrocarbons. A reaction solvent is preferred since the reaction is exothermic and the dissipation of heat is thus enhanced.  
  The reaction is suitably conducted at a temperature between about 2()C. and about 150C. and a temperature between about 50C. and lC. is preferred. The reaction occurs at temperatures above and below the suitable temperature range but at temperatures below about 2()C.. the reaction rate is too low to be practical. and at temperatures above about 150C. the reaction rate is high and the reaction is difficult to control unless high pressure apparatus is used.  
  The reaction pressure is suitably atmospheric or superatmospheric pressure. and autogenous pressure is presently preferred. Pressures of 1 atm. to 40 atm. are typical at temperatures of 25C. to 120C.  
  The reaction is preferably conducted under substantially anhydrous conditions.  
  The reaction time will vary in accordance to the reactivity of the R-(-CX;,),, reactant, the catalyst used and the reaction temperature. Generally a reaction time of a few minutes to a few days is sufficient for the reaction to be substantially completed, e.g., about 1 to about 96 hours. In most instances, 4 to 24 hours at the preferred reaction temperatures is adequate for the reaction to go to substantial completion. The more highly substituted compounds, particularly those wherein the sub- SPECIFIC EMBODIMENTS The following examples further illustrate the invention.  
 GENERAL EXPERIMENTAL PROCEDURE A catalytic amount of Lewis acid catalyst was added to 0.1 mole of trihalomethyl-containing reactant. The mixture was cooled in liquid nitrogen and 0.2 mole of liquid SO was added. The reaction vessel was sealed. warmed to reaction temperature and held at that temperature until the reaction was substantially completed, cooled to room temperature and opened to the atmosphere. The volatile components were removed under reduced pressure, and the acid halide product obtained from the reaction mixture by distillation under reduced pressure or by solvent extraction with an appropriate solvent.  
 EXAMPLE 1 Preparation of Trichloroacryloyl Chloride AlCl CCl =C(Cl)-CCl S0 A l? cc1 =c(c1) -c-c1 S0612.  
  In accordance with the above general procedure. 0.5 g. (0.0038 mole) of anhydrous AlCl,, was mixed with 24.9 g. ((llmolc) of pcrchloropropene and 12.8 g.  
 (0.2 mole) of S The reaction mixture was warmed at 90C. for 39 hours in a sealed, glass polymer tube.  
 of a catalytic amount of AlCl The results are summarized in Table III.  
 TABLE III React-ant Product; B To. erature C. Tine (hours! Yield It 1. p-Cl C-C H -CCl P-ClH-C H -C-Gl 85 39 100 S? 2 p-Cl C-C Clu-C0l p-Cl-CC Cl -C-Cl 8O 2O 90 9 E? 3. C H -CF C H -G-F 0 3 -0-01 90 48 l E. 4. p- (c1 c-c c1 p-(ClC-C Cl 6o 17 65 ll The product yield of C H -CF from 3 above was increased by using BF rather than AlCl as the 6 5 3 3 catalyst.  
 Upon distillation, 13.3 g. of triehloroacryloyl chloride (69% yield, based on perehloropropene) and 8.2 g. o thionyl chloride (69% yield) were obtained.  
 EXAMPLE 2 Preparation of Benzoyl Chloride 0 11 -001 so E, C H -8-Cl socl In accordance with the above general procedure, 5.0 g. (0.037 mole) of anhydrous ZnCl was mixed with 7.82 g. (0.04 mole) of benzotriehloride and 5.0 g. (0.08 mole) of S0 The reaction mixture was warmed at 120C. for 48 hours in a sealed glass polymer tube. Upon distillation, 3.23 g. of benzoyl chloride (58% yield, based on benzotrichloride) was obtained.  
  Two other identical reactions were conducted as above except that in one reaction AlCl was used rather than ZnCl and FeCl replaced ZnCl in the other reaction. The best product yield was obtained in the AlCl catalyzed reaction.  
  Under similar reaction conditions and ratio of reactants, several reactions were conducted in the presence We claim:  
  1. A process for preparing organic acid halides comprising reacting by contacting in the liquid phase (a) sulfur dioxide and (b) an organic compound bearing at least one allylic or benzylic trihalomethyl group; the halogen of said trihalomethyl group being fluoro, ehloro, bromo or mixtures thereof; said process being conducted in the presence of a small but catalytic amount of BF;,, BF,,.etherate, SnCL, or ZnCl. and at a temperature of from about 50C. to about C.  
  2. The process defined in claim 1 wherein each trihalomethyl group is trifluoromethyl and the catalyst is BF or Bficthcratc.  
 3. The process defined in claim 1 wherein the catalyst is present in an amount of from 0.01 to 1 percent based on the weight of (b).  
  4. The process defined in claim 1 wherein the reaction is conducted in a solvent.  
  5. The process defined in claim 4 wherein said solvent is sulfur dioxide.  
  6. The process dcfined in claim 1 wherein the reaction pressure is autogenous.