United States Patent Office

Patented Sept. 30, 1952 2,612,514 UNITED STATES PATENT OFFICE PRODUCTION OF ESTERS OF RELATIVELY STRONG ORGANIC AND NORGANICACDS WITH ALPHATIC COMPOUNDS HAVING MORE THAN ONE CARBON ATOM Edwin P. Plueddemann, Toledo, Ohio, assignor to Food Machinery and Chemical Corporation, Wilmington, Del, a corporation of Delaware. No Drawing. Application June 4, 1947, Serial No. 752,557 6 Claims. (CI. 260-46) 1. 2 This invention relates to methods of produc pared in good yields from readily available ma ing higher organic esters of relatively strong acids terials. and to certain esters producible by said methods Broadly considered, the process of the present as new compounds. More particularly the process invention involves mixing a higher organic basically involves the reaction of higher organic 5 chloride, such as benzyl chloride, with a methyl halides with methyl esters of relatively strong ester of a relatively strong acid such as trimethyl acids in the presence of an amine catalyst in phosphate, and with a catalytic or Small amount which reaction methyl halide is liberated and of an amine, and heating the resulting mixture the higher organic radicals replace the methyl at an elevated temperature until methyl halide groups forming new or different esters. As new () is liberated and a higher Organic ester of the acid, compounds, there may be mentioned tri-chloro as tribenzyl phosphate, is obtained. The methyl butenyl phosphate and tri-chloropropenyl phos chloride is preferably allowed to escape as it phate. forms and is led through a condensing chamber Neutral esters of strong mineral acids such as to storage. The higher ester may then be recov phosphoric and sulfuric have heretofore been ered in purified form from the residual reaction prepared (1) by reacting the acid chloride with mass by distillation or crystallization or by any alcohols, removing HCl by Suitable means and re other suitable method. covering the ester or (2) by reacting an alkyl The catalytic nature of the process is conclu halide With the Salt formed from a heavy or 'sively revealed by heating trimethyl phosphate active metal such as silver, yielding the ester and or other methyl ester with a reactive chloride silver halide as a by-product, or (3) by special such as benzyl chloride to a temperature in ex methods of limited applicability. Direct esterifi cess of 150° C. first in the absence of an amine, cation of the acid with alcohols or “ester ex and second, in the presence of an amine. In the change' reactions of an available ester with an first instance no appreciable reaction occurs, but other alcohol have not been successfully applied when a small amount of tributyl amine or other in the preparation of these esters. The use of amine is added, a vigorous reaction occurs re silver or other heavy metal salts is too costly...to Sulting in the rapid evolution of methyl chloride be of commercial value. and the displacement of the methyl radicals, of Esterification with certain alcohols may also the phosphate by the benzyl radicals. be impractical because of the high cost of the The reaction is preferably, carried out in the alcohols or because of the difficulty of controlling 20 presence of an addition of a small amount of certain alcohol esterifications. Allylic alcohols potassuim carbonate, soda ash or other anhy such as allyl, methallyl, benzyl, 3-chloro-2- drous base which combines with any acid lib propenyl, and 3-chloro-2-butenyl alcohols are erated by side reactions during the period of more expensive than the corresponding halides, heating. Yields are substantially improved and great difficulty is encountered in preparing through this procedure. strong acid esters of these alcohols by any method During the heating operation, the tempera generally used. ture rises to a point above 100° C. where any Certain of these esters have been reconnended moisture present is vaporized off and reaction as monomers for copolymerization with other commences to occur. The optimum reaction materials in the preparation of plastic masses, temperature varies according to the strength or or as high boiling plasticizers, but have not come ionization constant of the acid, and according into prominence because they have not been to the reactivity of the particular organic readily available by known methods of prepara chloride selected, but temperatures between 120° tion. and 170° C. have generally been found most sat Accordingly an object of the present invention isfactory. Lower temperatures, however, may be is to provide a commercially acceptable method used with various more reactive mixtures and of producing known esters suitable for use in the higher temperatures may be required with less above-mentioned and other fields. Another ob reactive mixtures. Temperatures above 200° C. ject is to provide new esters which, because of or higher cannot ordinarily be employed because their low volatility, good compatibility and pro at Such levels, decomposition and side reactions nounced fire resistance, have value as Solvents are likely to occur. and plasticizers for plastic masses, coatings and The nature of the catalytic action has not been the like. As to all of the esters, it is an object definitely determined but it appears that. the to provide processes whereby they may be pre 5. 5 amine catalyst acts through an intermediate 2,612,514 3 4. quaternary ammonium compound formed by its much larger excess may be used without penalty reaction with the higher organic chloride. This except for the decreased yield per volume of explanation of the reaction is indicated inasmuch reactor space and the additional processing re as quaternary ammonium compounds Such as tri quired to recover the added excess. At the other methyl benzyl ammonium chloride have a cata 5 extreme, an excess of methyl ester may also be lytic activity equal to that of free tertiary amines. used to obtain maximum reaction of the halide. It is recognized as possible, however, that the . Any unreacted methyl esters may then be re amine catalyst might react first with the methyl covered and recycled. ester to cause dissociation of the acyl ion and The methyl esters employed in the processes the tetraalkylammonium ion. is . O of the present invention hereinbefore described In certain instances equimolar quantities of as methyl esters of relatively strong acids, include tertiary amine may first be warmed with the alkyl derivatives of those organic and inorganic acids halide to form a quaternary ammonium salt which are commonly referred to as being strong which may then be heated with a methyl ester and moderately Strong acids. Among the acids to liberate methyl halide and form the alkyl l; whose methyl esters have been tested and found ester. Such a procedure may be especially help satisfactory there may be mentioned in particu ful in the preparation of esters from low boiling lar, phosphoric, alkyl phosphoric, Sulphuric, Sul halides such as allyl chloride or bromide which fonic, oxalic, maleic, phosphorous, and phos do not react with methyl esters at their reflux phonic acids, which may be referred to generally temperatures. 20 as oxygen-Containing acids. These acids in one. The chlorides, bromides and iodides of the embodiment of the invention are employed in various types of organic compounds hereinafter the form of their simple, esters, examples, of the disclosed contain more than one carbon atom, same being dimethyloxalate, trimethylphosphate the preferred. examples being octyl chloride and and dimethylsulfate. In an alternative embodi benzyl chloride in which the chlorine atoms are ment, such acids are employed in the form of joined to aliphatic radicals. Although the iodides their mixed, esters containing in addition to one and bromides sometimes react more readily, the or more methyl groups, one or more higher chlorides are preferred in view of their avail organic radicals, and when such esters are used ability and cheapness. Organic halides of any they react exclusively at the methyl ester link high molecular weight may be employed so long age or linkages. Thus, if a mixed methylalkyl as, they will react with tertiary amines to. form phosphate is reacted with an alkyl chloride, the quaternary ammonium Salts. Organic halides alkyl radical of the chloride replaces only the of eighteen carbon atoms react just as effectively methyl group or groups of the mixed phosphate. as those of eight carbon atoms. The alkyl group of the chloride is selected such The organic component of the halide may be that it is identical with the alkyl group of the aliphatic, or it may be cycloaliphatic, or hydro phosphate. employed if it is desired to produce a aromatic, or aromatic-aliphatic, the halogen simple trialkyl phosphate. Mixed trialkyl phos. atom in each case preferably being, joined to the phates can be produced by selecting an alkyl aliphatic radical thereof, the said compounds chloride of a different alkyl radical than that being hereinafter referred to generically as "ali 40 of the methyl alkyl phosphate used. phatic halide compounds.' It may be a pure pri In place of the simple or mixed esters, the pres mary or secondary, normal, or branched chain ent invention in another embodiment contem alkylchloride or other chloride, a mixture of plates employing alkali metal salts of methyl acid pure primary and secondary chlorides, a mixed esters of polybasic acids, as for example the so primary-secondary dichloride, a mixture of chlo dium and potassium salts of methyl acid phos rides such as those obtained by chlorinating a phates. If methyl dipotassium phosphate is re hydrocarbon fraction, or a long chain polyhalide acted with an alkyl chloride in the absence of an such as a polyvinyl chloride. amine catalyst, a mixed methyl dialkyl phosphate The organic radical of the halide may be either is obtained.

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