Patented Oct. 10, 1939 2,175,805

UNITED STATES PATENT OFFICE 2,175,805 STABILIZED ORGANIC NITRILE AND PROCESS OF MARING Ralph A. Jacobson, Wilmington, Del, assignor to E. I. du Pont de Nemours & Company, Wil mington, Del, a corporation of Delaware No Drawing. Application June 8, 1937, Serial No. 147,055 6 Claims. (C. 202-57) This invention relates to the preparation of Sure, pure glycolonitrile is obtained in excellent glycolonitrile and more particularly to improve yields. I have likewise discovered that, by main ments in its manufacture from formaldehyde and taining the pH of the pure distilled product at hydrogen cyanide. The invention relates further less than 7 and preferably at less than 6, the to treatment of the product for the purpose of product can be retained unchanged for an in- 5 preserving it. definite period. If the pH is not kept definitely Glycolonitrile, also properly called formalde On the acid side during reaction and distillation, hyde cyanhydrin, is a known compound of the much tar is formed, the yields of glycolonitrile formula: are unsatisfactory, and there is ever present the O B OH threat of sudden decomposition. Furthermore, 0 N / if the pure distilled glycolonitrile is allowed to / stand for a few days without acid having been B CN added, it will usually polymerize suddenly and A number of methods for its preparation are violently with the formation of tar. The pres 15 given in the literature, among them the treat ence of an acidic compound during synthesis and is ment of aqueous formaldehyde with potassium purification, and the addition of one to the dis-, cyanide and sulfuric acid, the treatment of form tilled product, eliminates these difficulties and aldehyde with aqueous hydrogen cyanide, and the makes it possible to prepare, distill, and keep the treatment of paraformaldehyde or trioxymethyl glycolonitrile without change. ene with hydrogen cyanide in the presence of an The more detailed practice of the invention is 20 alkali. Due to the ease with which glycolonitrile illustrated by the following examples, in which polymerizes, however, the yields obtainable from parts given are by weight unless otherwise stated. known processes, such as the above, have been There are, of course, many forms of the inven low. In fact, a glycolonitrile prepared in accord tion other than these specific embodiments. with the usual methods polymerizes spontane Ously in a few days to a solid product which is Eacample I useless as an intermediate for the preparation of To 688 parts of 37% aqueous formaldehyde, many compounds and unfitted for many other cooled to 5 C., was added 228 parts of liquid hy uses to which the monomeric compound can drogen cyanide. The mixture was kept at 0 to 5 be put. C. for 4 hours, allowed to stand overnight at 30 An object of the present invention is to provide about 25°C., acidified with about 2 parts of aque a process for preparing glycolonitrile, recovering ous 85% o-phosphoric acid and warmed on the it from the crude reaction product, and keeping steam bath for 4 hours in a flask containing a re it as a stable monomeric liquid for an indefinite flux condenser. The crude reaction product was ', period of time. Another object of the invention then distilled in vacuum from a bath maintained 35 is to prepare glycolonitrile from formaldehyde and at 125 C. Following the removal of the water, hydrogen cyanide under conditions which prevent the cyanhydrin passed over as a colorless liquid its polymerization and give exceptionally high boiling at 95 C. under 12 mm. pressure. The yields of a pure product. Yet another object of yield was 482 parts or 94.3% of the theoretical. the invention is to make available a stabilized The colorless anhydrous product was stabilized by 40 glycolonitrile. Other objects of the inventiori adding thereto 85% aqueous o-phosphoric acid in will hereinafter appear. the ratio of about 2 parts of acid to 500 parts of Briefly stated, the above objects are accom glycolonitrile. plished by treating aqueous formaldehyde with Eacample II hydrogen cyanide in the presence of an acidic To a mixture of 1177 parts of 37% aqueous 4 compound, such as phosphoric acid, sulfuric acid, formaldehyde and 391-parts of hydrogen cyanide, tartaric acid, phthalic anhydride, and the like, which had been prepared at 0 to 5° C. and main distilling at subatmospheric pressure the product tained at this temperature for 4 hours, 1.47 parts resulting from the reaction and acidifying the of tartaric acid was added and the mixture heated distilled glycolonitrile. for 4 hours in a boiling water bath. The crude 0 I have discovered that if aqueous formaldehyde reaction product was then subjected to vacuum and hydrogen cyanide are mixed in stoichiomet distillation. Following removal of the water, the ric proportions at 0 to 5 C., and the mixture glycolonitrile was collected as the fraction boil acidified slightly, warmed at 70-80° C. for several ing at 92° C. under 11 mm. pressure. The yield : hours and then distilled at subatmospheric pres was 726 parts or 87.8% of the theoretical. The 2 2,175,805 product was stabilized by adding thereto about 2 mixture at from 70 to 100° C. for four hours, but parts of 85% aqueous o-phosphoric acid per 500 the same result can be obtained by using longer parts of glycolonitrile. Equally good results are periods at lower temperatures, or shorter peri obtained if the tartaric acid of the example is Ods at higher temperatures. Temperatures ex replaced by 1.5 parts of 95% sulfuric acid, or by ceeding 100° C. are unnecessary and therefore 1.47 parts of phthalic anhydride. not to be recommended. The reaction may be The Stabilizing effect of various acids on gly Carried out under reduced, normal or elevated colonitrile is shown by the following experiments. preSSures as desired. Samples of glycolonitrile containing 0.28% by It is desirable to conduct the distillation at a O Weight of several different acids were allowed to bath temperature of 125° C. or less, necessitat O Stand at room temperature alongside samples of ing in turn pressures of 12 mm. or less, in order pure anhydrous unstabilized glycolonitrile and of to avoid discoloration and decomposition of the glycolonitrile containing 0.28% of aniline and of product, which begin to be evident at about 125 Sodium hydroxide. The results were as follows: C. and increase with increasing temperatures. It is also desirable to heat the distillation vessel 15 indirectly, as through a suitable oil, Sand, or Added agent Stability period metal bath. None------Suddenly decomposed to a tar at the It has been found that o-phosphoric, tartaric, end of 6 days. phthalic, and Sulfuric acids are well adapted for 20 0.28% phosphoric acid--- Stilgear and colorless after 6 mos. the stabilization of the reaction mixture during 0.28% sulfuric acid.------0. 20 0.28% hydrochloric acid.--- Do, the preparation of glycolonitrile, and during its 0.28% nitric acid------Do, 0.28% acctic acid. Do. Subsequent vacuum distillation. These acids are 0.28% formic acid- Do. also particularly efficacious for stabilization of 0.28% propionic acid- DO. 0.28% phthalic acid. Do. the product. However, any stable acidic con 25 0.28% boric acid. Do pound can be used, providing only that it does 25 0.28% sodium hydroxide DfEposed violently at the end of 5 OS not volatilize or decompose so readily as to be 0.28% aniline------DEposed violently at the end of 12 dissipated during the early part of the distilla OS tion and providing, in addition, that it does not decompose the glycolonitrile with consequent dis 30 It is apparent from the above data that pure sipation of its own acidic properties. Acid an 30 anhydrous glycolonitrile of neutral reaction is hydrides such as acetic anhydride, butyric an unstable and eventually decomposes to a tar. hydride, propionic anhydride, maleic anhydride The data also show that the addition of an and phthalic anhydride as well as inorganic or alkaline-reacting material such as sodium hy Organic acid SaltS Such as annonium acid Sull droxide reduces the stable period to a matter of fate, ammonium acid sulfite, sodium acid phos 35 a few hours. Even such a weak base as aniline phate, sodium acid sulfate, methylamine hydro markedly accelerates the decomposition of gly chloride, anilin hydrochloride, and dimethylam Colonitrile, even though present in very small ine hydrobromide are also effective stabilizing amounts. On the other hand, the presence of a agents during reaction and distillation, since trace of acid renders glycolonitrile completely they impart to the Solution a pH of less than O stable. 7.0 and preferably less than 6.0. As to the Thirty-seven per cent aqueous formaldehyde, amount of acid or acidic compound required, a Commercially designated as formalin, and Ordi fraction of 1% is usually sufficient, i. e., about nary Connercial hydrogen cyanide may be used 0.2 to 0.3% of the combined weight of hydrogen Satisfactorily in the above designated proc cyanide and formaldehyde calculated on an an sts eSSeS. If desired, however, paraformaldehyde or hydrous basis. There is no objection to using trioxymethylene can be used in whole or in part. considerably larger announts Such as in the range Water or lower aliphatic alcohols and esters, in of 1 to 5% providing that proper care is used particular methanol, ethanol, n-propanol, iso during the end of the distillation to avoid too butanol, ethyl acetate, and methyl propionate great a concentration of Strong in Organic acids, 59 Inay be used as solvents or diluents. Gaseous such as Sulfuric acid, from accumulating. formaldehyde can be used in lieu of aqueous Stabilized glycolonitrile has been found use formaldehyde by passing it into the hydrogen ful for a variety of purposes. It may be used Cyanide in Water or a solvent of one of the above as an intermediate for the preparation of de types. In the specification and claims “form tergents, as a solvent for certain types of resins 55 aldehyde' will include the polymeric or mono and plastics, and as an insecticide. However, it meric form of the aldehyde whether in liquid, or is chiefly useful as an intermediate for the prep Vapor phase or in solution. aration of other compounds such as ethanolam The proportions of formaldehyde to hydrogen ine (by reduction), ethylene-diamine (by reduc 60 Cyanide can be varied over a considerable range tion in ammonia), glycolamide (by partial hy Such as 2 mols of either reactant to one of the drolysis), glycolic acid (by hydrolysis), glycine Other, but stoichoimetric proportions of the re nitrile (by annination), glycine (by amination actants are desirable since no recovery of ex and hydrolysis), and glycine esters (by amina CeSS reagent is then necessary. tion, hydrolysis, and esterification). Esters of 5. Considerable latitude in temperature is pos glycolonitrile Such as the acetate, formate, bu Sible though it is preferable to mix the reagents tyrate, and isobutyrate are useful as Solvents in the cold because of the low boiling point of and insecticides. liquid hydrogen cyanide. This permits the re From a consideration of the above Specifica action to proceed slowly without loss of either tion, it will be appreciated that many changes O reagent. Alternatively, however, the hydrogen may be made in the details and proportions O Cyanide can be added above its boiling point therein given without departing from the inven (26 C.) by leading it as a vapor into the form tion or sacrificing any of the advantages that aldehyde Solution maintained at temperatures of may be derived therefron. from 20 to 100° C. After the initial reaction I claim: has occurred, it is preferable to maintain the 1. A process of distilling glycolonitrile from an s

2,175,805 3 aqueous medium which comprises distilling the distillate an acidic compound of such nature and glycolonitrile from the aqueous medium at a pH in such amount as to adjust its pH value to less of less than 7. than 7. 2. A process of distilling glycolonitrile from 5. A process which comprises distilling gly 5 5 an aqueous medium which comprises adding an colonitrile from an aqueous solution maintained inorganic acid to the aqueous medium contain at a pH value of less than 7 by the addition of ing the glycolonitrile to lower the pH to less than o-phosphoric acid and subsequently acidifying 6 and subsequently conducting the distillation the distillate with o-phosphoric acid. While maintaining the pH below 6. 6. A process for the distillation of glycoloni 3. A process of distilling glycolonitrile from an trile which comprises acidifying an aqueous me 0 O acqueous medium which comprises adding o-phos dium containing glycolonitrile with 85% o-phoS phoric acid to the aqueous medium containing phoric acid to adjust the pH value of the medium the glycolonitrile prior to distillation, to adjust to less than 6, distilling the glycolonitrile from the pH value of the medium to less than 6 and Said acidified medium at a pressure of approxi 15 subsequently distilling the glycolonitrile from mately 12 mm. to collect therefrom a condensate the medium maintained below a pH of 6. comprising a colorless, anhydrous glycolonitrile 4. A process which comprises distilling gly product and finally acidifying the condensate colonitrile from an aqueous solution maintained with o-phosphoric acid. - at a pH value of less than 7 and adding to the RALPH. A. JACOBSON.

y