Patented June 13, 1950 y, ...... 2,511,487

UNITED STATES PATENT of FICE SYNTHESIs oFIMINoDIACEToNITRILE Henry T. Thompson, Easton, Pa., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del, a corporation of Delaware ... No Drawing. Application August 8, 1946, serial No. 689,207 3 Claims. (CI. 260-465,5) This invention relates to the synthesis of ni practice of the invention, provided, of course, triles and particularly a new method for pre that care is taken to avoid the presence of even paring iminodiacetonitrile, HN (CH2CN)2. Small traces of alkali. The invention, therefore, Iminodiacetonitrile has been prepared hereto contemplates the synthesis of iminodiacetonitrile fore by reaction between hexamethylenetetra by heating aminoacetonitrile with formaldehyde mine and hydrogen cyanide, but the process has Cyanhydrin in the aforesaid molal proportions, been unsatisfactory and wasteful because of the but preferably in about equimolal quantities, in poor yield of imododiacetonitrile obtained, and the absence of alkaline catalysts. because the reaction is so slow that it requires In a Specific embodiment, the present inven several days for completion. . . stion contemplates the Synthesis of iminodiaceto It has also been disclosed heretofore Polstorff nitrile by heating substantially equimolal quan and Meyer, Ber. 45, 1905-12 (1912) that in the tities of aminoacetonitrile and formaldehyde synthesis of nitrillotriacetic acid by reaction be cyanhydrin at a relatively high temperature tween potassium cyanide and aqueous formalde within the aforesaid range, whereby a rapid re hyde, minor amounts of potassium iminodiacetate action between aminoacetonitrile and formalde are produced. Polsdorff and Meyer have attempt hyde cyanhydrin takes place without excessive ed to explain the formation of potassium iminodi decomposition of the reactants, thus producing acetate by postulating that under the alkaline iminodiacetonitrile in very good yield. There conditions prevailing a reaction may take place fore, in a preferred method of practicing the in between amino-acetonitrile and formaldehyde s20 vention, the said reactants are heated at a tem cyanhydrin to form iminodiacetonitrile which perature of about 140° C., in the absence of alkali, may then react with the alkali to form the salt of whereby a reaction producing-iminodiacetonitrile iminodiacetic acid. The said postulated process, takes place. Decomposition due to prolonged however, has not been useful for the synthesis of heating is prevented by stopping the reaction iminodiacetonitrile. after a total reaction time not exceeding about 15 An object of this invention is to provide a proc minutes, preferably by quickly cooling the mix ess whereby iminodiacetonitrile may be prepared ture. Under the aforesaid preferred conditions, without appreciable loss of nitrile. Another ob only a small quantity of tarry by-product result ject is to provide a process for the manufacture of ing from the decomposition of the constituents iminodiacetonitrile which produces the said ni 30 of the reaction mixture is produced. The tem trile substantially free from contamination by perature range Within which this rapid reaction other materials such as nitrilotriacetonitrile. takes place Without the formation of excessive These and other objects are accomplished in quantities of decomposition products is some accordiance with this invention by reacting ani what narrow, preferably about 135° C. to 150° C. noacetonitrile with formaldehyde cyanhydrin at 35 The aminoacetonitrile used as one of the react a temperature of about 50° C. to 150° C., in the ants: in accordance with this invention may be absence of alkali (i. e., alkaline materials such prepared by heating, formaldehyde cyanhydrin as hydroxides, carbonates, cyanides, etc. of the with anhydrous ammonia, or by any other suit aikali metals, alkaline earth metals and the like), able process. While pure aminoacetonitrile may the initial molal, radio of aminoacetonitrile to 40 be used, it is frequently convenient to employ formaldehyde cyanhydrin being about 1:0.3, to aminoacetonitrile in the form of an aqueous solu 1:1.5. In contrast with the postulated process tion. Similarly, the formaldehyde cyanhydrin of Polsdorff and Meyer, it has been discovered employed in the practice of the invention is pref in accordance with this invention that, at slightly erably anhydrous formaldehyde cyanhydrin elevated temperatures, aminoacetonitrile and 45 which may be prepared by reacting formaldehyde formaldehyde cyanhydrin, in the presence of with hydrogen cyanide and distilling the result alkali, are rapidly (and Sometimes violently) de ing mixture in the presence of an acidic sta composed, So that it is essential in the practice bilizer at diminished pressures. If desired, aque of this invention to eliminate any traces of alka ous solutions of formaldehyde cyanhydrin may be line catalysts. One method for accomplishing 50 employed in place of the purified formaldehyde this result is to add to the reaction mixture about cyanhydrin. Moreover, the formaldehyde cyan 0.001 to 0.5% of a mineral acid stabilizer, based hydrin may be formed in situ from formaldehyde on the initial weight of the formaldehyde cyan and hydrogen cyanide in the presence of an acid hydrin. The presence of the said mineral acid reacting substance. The acid-reacting materials Stabilizer is not indispensably necessary in the 55 in general are suitable as stabilizers for the react 2,511,48? 3 4. ants employed in the practice of the invention, give outstanding results. Any convenient the preferred stabilizers being mineral acids, par method may be employed for separating imino ticularly phosphoric acid. diacetonitrile from the crude reaction product, In one manner of carrying out the invention, such as crystallization from any of the common the formaldehyde cyanhydrin and aminoaceto organic solvents. nitrile are mixed together and heated in a flask Since many different embodiments of the in for the required reaction time, and the resulting vention may be made without departing from mixture is thereafter chilled whereby the imino the spirit and scope thereof, it is to be under diacetonitrile separates therefrom in the form of stood that I do not limit myself except as set crystals. 10 forth in the following claims. The invention may be illustrated further by I claim: means of the following examples: 1. A process for the synthesis of iminodiaceto Eacample 1-A mixture containing 17.1 grams nitrie - Which comprises heating aminoaceto of aminoacetonitrile and 5.8 grams of formalde nitrile with formaldehyde cyanhydrin at a tem hyde cyanhydrin (containing a few drops of 5 perature of about 100° to 150° C., in the presence phosphoric acid per liter) was heated on the y of about 0.00 to 0.5% of a mineral acid Stabilizer steam bath at a temperature of about 100 C. for based on the initial weight of the formaldehyde one hour. The resulting mixture was cooled by cyanhydrin, the initial molal ratio of amino means of an ice bath whereby crystals of imino acetonitrile to formaldehyde cyanhydrin being diacetonitrile were deposited. The yield of 20 about 1:0.3 to 1:1.5, and thereafter separating iminodiacetonitrile was about 70% of the ininodiacetonitrile from the resulting mixture. theoretical. 2. The process set forth in claim 1, in which Eacample 2-The mixture containing 58 grains the said mineral acid stabilizer is phosphoric acid. (one mol) of formaldehyde cyanhydrin and 57 3. A process for the synthesis of iminodiaceto grams (one mol) of aminoacetonitrile was heated 25 nitrile which comprises heating a reaction mix together in a flask by means of an oil bath until ture consisting of aminoacetonitrile and formal the reaction mixture reached a temperature of dehyde cyanhydrin in equimolal proportions at 140° C. After about, 5 minutes, a vigorous re a temperature of about 135° to 150° C., whereby action took place with evolution of hydrogen a reaction producing iminodiacetonitrile takes cyanide and water. The reaction mixture was 30 place, maintaining the resulting reaction mix maintained at a temperature of 140° C. for a total ture at the said reaction temperature for a total reaction time of 15 minutes. Upon cooling, the reaction time not exceeding about 15 minutes, product crystallized forming a reddish brown and thereafter cooling the resulting mixture and solid. Four such runs were made, after which separating iminodiacetonitrile therefron. the crude products were combined and imino 35 HENRY T. THOMIPSON. diacetonitrile was separated therefron by ex traction with hot benzene until only a brown REFERENCES (CITED resinous material remained. The inninodiaceto The following references are of record in the nitrile crystallized from the benzene on cooling file of this patent: in long, colorless needles. These were removed by filtration and dried. The total weight of UNITED STATES PATENTS iminodiacetonitrile thus obtained was 296 grams, Number Name Date which corresponds to a yield of about 78%. 2,085,679 Gluud et al. ------June 29, 1937 It is evident that numerous changes may be 2,175,805 Jacobson ------Oct. 10, 1939 made in the manner of conducting the reaction 45 2,205,995 Ulrich et al. ------June 25, 1940 between aminoacetonitrile and formaldehyde 2,228,271 Jacobson et al. ------Jan. 14, 1941 cyanhydrin without departing from the scope of 2,405,966 EOder ------Aug. 20, 1946 this invention. For example, the reaction may 2,407,645 BerSWOrth. ------Sept. 17, 1946 be carried out in a closed pressure-resisting ves FOREIGN PATENTS Sel, and at pressures higher than atmospheric. 50 The reaction heat may be dissipated through Number Country Date cooling coils, water-jackets, or other convenient 388,874 Great Britain ------Mar. 9, 1933 means. In embodiments in which an acidic 638,071 Germany ------Nov. 9, 1936 stabilizer is employed, the stabilizer may be re 673,590 Germany ------Mar. 28, 1939 moved in the form of an insoluble salt prior to 55 OTHER REFERENCES isolating the product, if desired. While in the examples the invention is illustrated by means Stadnikoff, Ber. Deut. Chem., vol. 40, pp. 1014 of batchWise operation, it is to be understood 1017 (1907). that excellent results also are obtained in con Polstorff et al., Ber. Deut. Chem., vol. 45, pp. 1905-1912 (1912). tinuous operation. In the continuous process, 60 tubular converters, within which the reactants Dubsky, Ber. Deut. Chem., vol. 49, pp. 1048-9 are heated at controlled short reaction times, (1916).