Patented Jan. 6, 1953 2,624,750 UNITED STATES PATENT OFFICE 2,624,750 PROCESS OF PRODUCING PEOSPERATE ESTER, Aphorase Pechukas, Akron, Ohio, assignor, by Inesne assignments, to Columbia-Souther Chemical Corporation, Pittsburgh, Pa., a cor poration of Delaware No Drawing. Application January 23, 1948, Serial No. 4,069 4. Claims. (C. 260-46) 2 This invention is concerned with the produc By using a nonsolvent for HC in the manner tion of esters of alcohols, particularly primary herein contemplated, the amount of HCl in the and Secondary alcohols. reaction mixture may be maintained low. This It is known that Various esters may be prepared is particularly true when the reaction mixture is by reaction of an acid halide with a primary or maintained at a temperature such that substan Secondary alcohol. This reaction proceeds with tial distillation takes place. In such a case the the evolution of the desired ester and hydrogen solubility of the HCl remains at a substantial halide. minimum and is removed substantially as soon as In certain cases this method has been found formed due to the distillation of the nonsolvent. objectionable since yields of the desired ester are O In general the process is initiated by introduc undesirably low and formation of by-products is ing a quantity of the nonsolvent into a reactor undesirably high. Frequently, it has been con equipped with a reflux condenser system. This Sidered essential to conduct the reaction in the condenser system has a suitable outlet to permit presence of hydrogen chloride acceptors, such as escape of HCl gas beyond the condenser. Heat pyridine or sodium hydroxide. 5 is applied to the reactor to cause vaporization and The present invention provides a simple method reflux of the nonsolvent. Thereupon alcohol and Whereby esters may be prepared by reaction of acid chloride are added continuously or periodi alcohols particularly primary and secondary al cally in relative amounts required to react and cohols in high yield, without the use of an hydro to form the corresponding ester. gen chloride acceptor Such as pyridine and With 20 During the reaction, the temperature of the out excessive formation of by-products. In ac reaction mixture is maintained at a level at which Cordance With this invention it has been found Substantial distillation of the nonsolvent OCCUIS. that esters may be prepared in high yield, fre The rate of such distillation should be sufficient quently higher than prior art processes, and in a to ensure removal of HCl substantially as fast as simple and economic manner by reacting a pri 25 it is evolved. mary or secondary alcohol with an acid halide, The process is continued by adding reactants Such as an acid chloride, in liquid phase and in periodically or continuously and nonsolvent is re the presence of a liquid solvent which is a solvent turned or added to the mixture at a rate Sufficient for the alcohol, acid chloride and ester of the to replace that distilled off. If the process is alcohol and Which essentially is a nonsolvent or 30 conducted in a continuous manner, Suitable poor Solvent for the hydrogen chloride evolved means are provided for drawing off a quantity during the reaction. In this process, the tem of the mixture during the operation. perature of the reaction mixture is maintained Various solvents for the alcohol and the acid at the boiling temperature whereby substantial chloride which are nonsolvents for HCl may be distillation takes place, and sufficient of the non 35 used. Such “nonsolvents' are liquids in which Solvent is maintained present to ensure removal the solubility of HCI at their boiling temperature of HCl substantially as soon as formed and to is low, for example of the order of one percent reduce the solubility of HCI in the reaction mix by weight of HCl or below. In general non ture to a low Value. As a consequence, hydrogen oxygenated solvents having boiling points of 0 chloride Which is evolved during the reaction is 40 to 200° C. are suitable. Such solvents or 'non carried from the solution with the vaporizing solvents’ should be substantially miscible with OnSolvent. This Vapor mixture passes through the ester being produced or at least have a rela a Suitable reflux condenser system for the purpose tively high solubility (for example 10 percent or of condensing the nonsolvent and returning it to more by weight) therein. the reaction mixture. Because of insolubility of A particularly effective class of solvents which the HC1 in the nonsolvent, only a minor quantity may be used as herein contemplated, are the or substantially none of the HCl escaping from hydrocarbon halides. Typical chlorinated hydro the reaction mixture is returned with the non carbons which have been found to be Suitable Solvent to the reaction mixture. are ethyl chloride, methylene chloride, chloro Chloride formation, previously encountered in 50 form, carbon tetrachloride, trichloro-propanes, a reaction of this character, is due, at least to a monochlorobenzene, trichloroethylene, perchloro large degree, to reaction of evolved hydrogen ethylene, difluoro-dichloro-methane and Ortho chloride With the ester and/or the alcohol to form dichlorobenzene. A further class of nonsolvents the corresponding Organic chloride (RCI). I which are Suitable for this purpose include liquid have found that HCl has substantial solubility in 55 hydrocarbons having the boiling points desired, many liquid esters such as are produced by re Such as heptane, hexane, cyclohexane, benzene, action of acid chlorides With alcohols. This fac Xylene, gasoline or toluene. The Selection of any tor promotes formation of chlorides, frequently particular nonsolvent will depend, to some degree to a serious degree. at least, upon the boiling point of the alcohol 2,624,750 3 4 undergoing esterification and the solubility of the may be reacted with other acid chlorides which alcohol in the nonsolvent, as will be readily contain the group understood by those skilled in the art. Especially effective nonsolvents for the purpose herein Con --C templated are methylene chloride and carbon O tetrachloride. where X is carbon, sulphur or phosphorus. Such The nonsolvent used should have a boiling point acid chlorides include phosphrous Oxychloride; below that of the alcohol or hydroxy compound sulphuryl chloride; chloroformates such as which is being esterified. However, it is usually methyl, ethyl, n-propyl, n-butyl, allyl, phenyl, desirable for the nonsolvent to have a boiling 10 crotyl, methallyl cinnamyl chloroformate or Sini point above room temperature, preferably above lar chloroformates of monohydroxy compounds, 50° C. and within 25 to 75° C. of the boiling point chloroformates of polyhydroxy alcohols Such as of the alcohol. For example, in reacting phenol ethylene glycol bis chloroformate, diethylene gly with thionyl chloride, better yields are obtained col bis chloroformate, triethylene glycol bis using monochlorobenzene than with methylene chloroformate tetraethylene glycol bis chloro chloride or carbon tetrachloride. The producer formate and 2,3-carbonyldioxypropyl chlorofor tion of sulfites of the lower aliphatic alcohols nate; chlorosulfinates corresponding to the containing up to 8 carbon atoms, is best accom above chloroformates such as diethylene glycol bis plished using solvents which boil at about 50 to chlorosulfinate; Organic carboxylic acid chlorides 125° C. and preferably having a boiling point 20 such as acetyl chloride, funnaryl chloride, phthalyl within about 25° C. of the boiling point of the Chloride, propionyl chloride, butyryl chloride, or alcohol. cinnamyl chloride. The invention also contem The amount of nonsolvent used should be Suf plates the production of esters from other acid ficient to ensure appreciable distillation of Solvent chlorides wherein an acidic hydrogen or hydroxy and to cause appreciable reflux thereof. No hard is substituted by halogen as in the case of silicon and fast rule may be laid down in this connection tetrachloride, titanium tetrachloride and partial since it has been found that a wide variation in esters of Such compounds. the ratio of solvent to alcohol-acid chloride mix The process is particularly concerned with the ture may be maintained so long as substantial preparation of esters of monohydric alcohols reflux or at least distillation of the nonsolvent 30 Which contain up to 8 carbon atoms. Thus, the from the reaction mixture takes place. Usually invention has been found to be applicable to the amount of nonsolvent present and the rate of the production of esters of methyl alcohol, ethyl vaporization thereof should be sufficient to estab alcohol, n-propyl alcohol, isopropyl alcohol, n lish a partial pressure due to nonsolvent vapol'S butyl alcohol, isobutyl alcohol, isoamyl alcohol, which is not less than about one-half of the Octyl alcohol, cyclohexyl alcohol, methyl hexyl partial pressure of the HCl vapor and preferably carbinol, benzyl alcohol, cinnannyl alcohol, Beta the nonsolvent vapor partial pressure should be phenyl ethyl alcohol, 2-chloroethyl alcohol, 2 at least 75 percent of atmospheric preSSure. Dur Cyano ethyl alcohol, 1,2-dichloropropanol and the ing the process, the concentration of the ester corresponding nitro- or bromo-alcohols or other formed in the reaction mixture increases and fre 40 Similar monohydric aliphatic, cycloaliphatic or quently the solubility of HCl in the reaction mix aryl alcohol. Esters of higher alcohols contain ture increases as the ester concentration in ing, for example up to 30 carbon atoms such as creases. In general, the amount of nonsolvent esters of stearyl alcohol, lauryl alcohol, nonyl in the reactor should not be less than 10 percent alcohol, oleyl alcohol, blown sperm alcohols, etc. by volume of the volume of ester being prepared also may be prepared. Moreover the invention which is present. For most purposes the Volume may be extended to the production of esters of Of nonsolvent Should be 0.5 to 5 times the Volume other compounds which contain an hydroxyl of ester present.