[CONTRIBUTIONS FROM The HavemeYER LABORATORIES OF COLUMBIA UNIVERSITY, No. 1.] THE ACTION OF ORGANIC ACIDS UPON NITRILS.' HE action of organic acids upon nitrils has been the subject of a number of investigations which have been reported from this laboratory at intervals during the past seven years. The nitrils and acids employed in the various experiments have been made to react under the influence of elevated temperature and pressure in sealed tubes. In nearly every instance a few drops of acetic anhydride have been added to the mixtures of acids and nitrils to insure anhydrous conditions within the tubes. This precaution is believed to increase the yield of the principal products of the reaction. The reaction between acetic acid and acetonitril, whereby Gautier found diacetamid to be produced,' suggested to Colby the idea of trying parallel reactions between other acids and nitrils. Colby and Dodge' experimented with a large number of monobasic acids and mononitrils of both the fatty and the aromatic series. Their results show that under conditions of heat and pressure : I. Fatty nitrils and fatty acids yield secondary amids. II. Fatty nitrils and aromatic acids yield fatty acids and aromatic nitrils. III. amids. Aromatic nitrils and fatty acids give mixed secondary IV. Aromatic nitrils and aromatic acids give secondary amids. One exception was noted under the fourth head by these authors. Not so much work has been done upon dibasic acids. Miller' and Seldner worked with fatty dibasic acids, the former with succinic and the latter with glutaric acid. They proved that the imids of these acids result under three different conditions. From I. Dibasic acid and acetonitril. 1 Read at the meeting of the New York Section, May 6, 1898. 2 Ztschr. anal. Chem., 1869, p. 127, or Compt. rend., 60, 1255. 8 Am. Chem. J., 13, 1. 4 This Journal, 16, 443. 5 Am. Chem. J., 17, 532. II. Dinitril and acetic acid, and III. Equal molecules of the dibasic acid and its nitril. Two years ago the author published his first experiments upon aromatic dibasic acids. Phthalic acid was first tried and its imid resulted by heating it with propionitril. In the following pages are given results obtained recently along the same line of experimentation. This work may be grouped under two heads. First, experiments with monobasic acids, simple and substituted; second, experiments with aromatic, polybasic acids. PART I. UPON THE ACTION OF FATTY NITRILS ON MONOBASIC AROMATIC ACIDS, WITH A PRELIMINARY NOTE ON MALONIMID. Before describing the experiments upon aromatic acids which compose the main part of this investigation, a few words upon some attempts to prepare the unknown imid of malonic acid may not be out of place, since in these attempts the methods employed were the same as those used in making the imids of the bibasic aromatic acids. Malonic Acid and Ethylene Cyanide.-Two tubes containing equal molecules of malonic acid and ethylene cyanide were made by Miller in 1893. The first tube, when heated, exploded at 196° C. The second one was heated at 150° C. for five and onehalf hours. This tube was set aside and when examined by me recently it was found that the contents were liquid and brown. Very strong outward pressure was noticed upon unsealing. Succinimid was found but no malonimid seems to have been produced. Malonic acid loses part of its carbon dioxide readily by heating, and for this reason it was thought better to use malonitril and treat it with glacial acetic acid. This method was unsatisfactory, too, for almost complete decomposition took place by heating. As throwing some light upon the question of the rearrangement of cyan acids to give imids, the next experiments were made upon cyanacetic acid. This acid was heated to 190° in benzol medium. There was strong pressure upon opening and the contents of the tube were evaporated upon the water-bath to drive off the benzol. The residue was extracted with absolute alcohol. This solution was treated with boneblack and by evap oration nearly to dryness and long standing a small amount of crystalline material separated. This was pressed and dried and recrystallized. It was soluble in acetone, ether, alcohol, and water, and almost insoluble in benzol. Its melting-point was 115° C. It gave a nitrogen test and was neutral in its reaction with litmus paper. By boiling with potassium hydroxide solution, acidifying and evaporating to dryness, and extracting with absolute alcohol, an acid was obtained melting at 130°, very soluble in water and alcohol. This seems to be malonic acid. It seems probable, therefore, that malonimid was produced by the rearrangement of the cyanacetic acid. Not enough of this supposed imid has as yet been obtained to make a thorough investigation, but the same material was obtained from two tubes made up and heated at different times and its further study will be interesting. Benzoic Acid and Ethylene Cyanide.-Two sealed tubes containing ethylene cyanide and benzoic acids and a drop or two of acetic anhydride were prepared. The first contained equal molecules and the second contained two parts of acid to one part of nitril. Both were heated seven hours at 145° C. and then five and a half hours at 195° C. The contents were then black and semi-solid and crystalline. In the first tube benzonitril was found. The contents of the tube were treated with weak sodium carbonate solution and then evaporated to dryness and extracted several times with ether. The operations thus far described were carried out by Dr. E. H. Miller, in 1893. The ether extract gave a white crystalline solid upon evaporation. This residue was very soluble in acetone. After recrystallization from water and twice from acetone, succinimid, melting at 124°C., was obtained in characteristic crystals. These were tested for nitrogen and it was found. The second tube contained originally three grams of ethylene cyanide and 9.15 grams of benzoic acid; i. e., two molecules of acid to one of nitril. No pressure was observed upon opening. A strong odor of benzonitril was at once apparent. The tube contents were liquid at the temperature of a hot water-bath and were poured into dilute sodium carbonate solution. From results obtained by Colby and Dodge and by Miller, it was thought that this tube might contain benzoic acid, ethylene cyanide, benzonitril, succinic acid, succinimid, and dibenzamid. Dibenzamid and succinic acid were not found. Colby and Dodge showed that by heating together benzoic acid and acetonitril at 250°-260° C. there was formed principally benzonitril and acetic acid. At about the same temperature benzonitril and benzoic acid combine to give dibenzamid. In our tube probably the temperature had not been carried high enough to produce this condensation. The primary reaction which seems to have taken place in both tubes is: C,H,COOH + C,H,(CN), = C,H,CN+ C,H,(CO), NH. The second tube was examined as follows: Upon pouring the contents into sodium carbonate solution three and one-half cc. of black liquid material separated at the bottom. This was drawn off by means of a separatory funnel and showed to be benzonitril. It was distilled with steam, separated from the water, partly dried by evaporation upon a water-bath, and then with small fragments of calcium chloride. The once purified product boiled at 188° (uncorr.). The boiling-point of benzonitril is given as 191° C. The sodium carbonate solution was evaporated to dryness and extracted with ether and then with water. The ether extract gave a residue upon evaporation which was succinimid. Recrystallized from acetone it gave oblong, colorless crystals (melting-point 125° C.). The water extract above mentioned by acidifying with hydrochloric acid gave a bulky precipitate. This, filtered off, washed, and dried, melted at 117.5°. It was unchanged benzoic acid. Recrystallized from hot water, large plates were deposited (melting-point 120° C.). These crystals are sublimable at the temperature of boiling water. 2.75 grams of benzoic acid were recovered, which is also about the amount of benzonitril produced. After the ether and water extractions of the original tube contents, a large, charred, carbonaceous residue and a little tarry matter, believed to be partly ethylene cyanide, remained. In Miller's dissertation upon succinimid are reported a number of attempts to prepare B-cyanpropionic acid in sufficient quantities to try whether it could be made to rearrange into its isomer, succinimid. It seems to me that these two experiments point to the formation of B-cyanpropionic acid as an intermediate product. Either it must be considered that the carboxyls of the benzoic acid change places with both nitril groups of one-half of the ethylene cyanide or with one of the nitril groups forming B-cyanpropionic acid, which rearranges into succinimid. Of course, if the first assumption is the correct one, the succinic acid formed would react with the unchanged ethylene cyanide and two molecules of succinimid would result as shown by Miller. It seems probable that had succinic acid been formed in either of these experiments some of it would have been found, for these reactions are not often complete. On the other hand, if B-cyanpropionic acid were the intermediate product we should not expect, because of its well-known instability, to find it withstanding a temperature of 195° unchanged. Only about one gram of succinimid was produced and this fact, together with the large amounts of decomposition-product, seems to strengthen the second assumption in regard to the course of the reaction. Phenylacetic Acid and Ethylene Cyanide.-Two tubes, the first containing equal molecules of phenylacetic acid and the second two molecules of acid to one of nitril, were prepared by Miller in 1893. Both tubes were heated for six hours at 150° C. The contents were then black and semi-fluid. Not much outward pressure was noticed upon opening. These tubes were set aside and not examined until 1898. The reaction in tube I seems to be: C.H..CH,.COOH + C,H,(CN), = CHỊCH,.CN+C,H,(CO),NH Phenylacetamid was also found in this tube and its presence cannot be explained except by the presence of some water in the tube which reacted upon the phenylacetonitril. The reaction of tube II was primarily the same as in I. The excess of phenylacetic acid then reacted with the phenylacetonitril and produced diphenyldiacetamid: CH..CH,COOH + C,H.CH,.CN = (C.H.CH,.CO),NH. No phenylacetamid was found in this experiment, but some phenylacetic acid was recovered. |