US2320034A - Method of preparing halogenated carboxylic acid esters - Google Patents

Description

' Patented 25, 1943 UNITED STATES PATENT OFFICE METHOD or PREPARING HALOGENATED caanoxruo ACID Esraas James D. DIanni, Akron, Ohio, assignor to Wingfoot Corporation, Akron, Ohio, a corporation of Delaware No Drawing. Application December 4, 1940,

' Serial No. 368,505

4 Claims. (01.260-487) This invention relates to an improved method for the preparation of certain esters of halogenated carboxylic acids and, more particularly, to the halogenation of esters of unsaturated carboxylic acids.

It has been attempted heretofore to chlorinate' CH==C-COO-CH3 c1: omc1-cc1-coo -cm on. on:

and the production of the dimer probably results from the following reaction:

Cl CHz-l -C O -CH2CX it is an object of the present invention to improve the yield of the desired dlchloro compound with a corresponding reduction in the amount of dimer which is produced. A further object is to extend the method to the treatment of esters of u aturated acids of a type similar to the acrylat s, that is to the halogenation of compounds w ich may be considered to be esters of beta drocarbon substituted acrylic acids. The reaction, as previously applied to the chlorination of methyl methacrylate, involves the addition of chlorine or other halogen to the acrylic ester and t it was observed that an excess of the ester was present. This excess of ester is believed to favor the production of dimer at the expense of the desired product. Accordingly, the present method is characterized by the maintenance of an excess of the other reactant, the halogen, at all times during the course of the reaction, one method of accomplishing this being to saturate anappropriate reaction medium with the halogen and then add the ester to this saturated medium gradually while still continuin to add. 'more halogen. In this way, the halogen is always present in excess of the ester. The results obchloro compound was obtained in prepondered amount and the residue, presumably the dimer, was much reduced in quantity.

To illustrate the method, the following example is given but it will be understood that the invention is not limited to the details therein given. Chlorine was passed into 400 ml. of chloroform, which was cooled in an ice bath and there was then added dropwise with stirring 100 grams of methyl methacrylate, the addition requiring about two hours. When starting the addition of the ester, the ice bath was lowered and the temperature of the chloroform allowed to rise to about 25-30" 0., at which point it was kept by occasional cooling. The flow of chlorine into the reaction medium was maintained during the ester addition so that an excess of chlorine was present at all times. When a permanent chlorine color had been attained, the reaction prod not was fractionated and there was obtained a yield of 126 grams, or 74%, of the desired methyl alpha, beta-dichloroisobutyrate. The product had a boiling point of 95-100 C. at mm., an index of refraction of N 1.4495, and a density of D 1.243. The molar refraction li/Ilt was 36.9; calculated for CsI-IaOaCh, 36.8. The residue, probably was dimer, amounted to 36 grams.

The method is of course applicable to the preparation of other esters of dihalocarboxylic acids such as the esters of alpha, beta-dichloroproplonic acid, alpha, beta-dichlorobutyric acid, alpha, beta-dichlorocaproic acid, alpha, betadichloroisocaproic acid, alpha, beta-dibromoisobutyric acid, diiodoisobutyric acid, and the alpha, beta-dihalo, beta-methyl butyric acids. Other important esters are those of oleic acid and undecylenic acid, which are commercially available.

The alcohol radical of the ester may be alkyl,

such as methyl, ethyl, propyl, isoprcpyl, butyl, isobutyl, amyl, isoamyl, cyclohexyl, cyclopentyl, chloroethyl, bromoethyl and chloropropyl or it maybe aryl or aralkyl, such as phenyl benzyl, alpha naphthyl, beta naphthyl, xenyl, phenethyl ,and' the like. As indicated, other halogens may be added in place of chlorine in the formation of esters related to those above mentioned, bromine and iodine being added in a similar manner.

The conditions of the reaction are such as will permit the maintenance of an excess of halogen in the reaction medium, the temperature being maintained between 0 and 50 C. but preferably in the neighborhood of 20-30 C. A suitable medium will be present to contain the halogen, chloroform being one but carbon tetrachloride,

"lined f l y confirm the theory since the di- 55 dichloroethane, CS2. acetic acidand other sclpreferred embodiments of the invention, it will be apparent to those skilled in the art that various modifications and changes may be made therein without departing from the spirit oi the invention or from the scope of the appended claims. i

I claim:

1. A method of preparing methyl alpha, beta-f dichloroisobutyrate which comprises saturating chloroform with chlorine and then' adding methyl methacrylate gradually to the solution while passing additional chlorine into the chloroform.

2. A method of preparing esters or dichloro carbcxylic acids which comprises chlorinating an alkyl ester of the class consisting c." the acrylates and the alpha alkyl-substituted acrylates while in solution and maintaining in the solution throughout the chlorination an excess of chlorine over that required to react with the ester.

3. A method'of preparing esters of dichloro carboxylic acids which comprises passing chlorine gas into a solvent to build up a substantial concentration of chlorine therein and then dissolving therein an alkyl ester of the class consisting of the acrylates and the alpha alkyl-substituted. acrylates and passing chlorine into the solution so that throughout the chlorination there is an excess of chlorlne in the solution over that required to react with the ester.

4. A method of preparing esters of dichloro carboxylic acids which comprises saturating chloroform with chlorine and then gradually adding to the resulting solution an alkyl ester of the class consisting of the acrylates and the alpha alkyl-substituted acrylates while passing addiv tional chlorine into the solution so as to maintain