Quantitative Study of the Preparations of Guanidine Nitrate and

Apr 21, 2017 - 2 An abstract of parts of the theses submitted by 0. F. Steinbach, Jr., .... guanidine nitrate recovered from the chilled solution. Thi...
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INDUSTRIAL A N D ENGINEERING CHEMISTRY

Vol. 23, No. 10

Acknowledgment

Literature Cited

Grateful acknowledgment is made to L. T. Alexander, Hubert Lakin, and Mrs. Dorothea M. Darnell, of the Soil Chemistry and Physics Division, Bureau of Chemistry and Soils, U. S. Department of Agriculture, for the large-scale separations and the mechanical analyses; and to L. F. Rader, Jr., of the Fertilizer Technology Division, for assistance in the chemical analyses. The samples of phosphate rock were kindly furnished by several of the phosphate mining companies.

(1) Alexander and Jacob, U. S. Dept. Agr., Tech. Bull. 214 (1930). (2) Assocn. Official Agr. Chem., Methods, pp. 4, 16 (1925). (3) Hill, Jacob, Alexander, and Marshall, IND. ENG.CHEM.,24, 1302 (1930). (4) Jacob, Hill, and Holmes, Colloid Symposium Annual, 1, 195 (1930). ( 5 ) Mansfield and Girty, U. S. Geol. Survey, Professional Paper 164, 213 (1927). (6) Olmstead. Alexander, and Middleton, U. S. Dept. Agr., Tech. Bull. 110 (1930). (7) Reynolds. Jacob, and Hill, IND. ENG. CREW.,21, 1253 (1929).

Quantitative Study of the Preparations of Guanidine Nitrate and Nitroguanidine” G. B. L. Smith, V. J. Sabetta, and 0. F. Steinbach, Jr. THEPOLYTECHNIC INSTITUTEOF BROOKLYN, BROOKLYN, N. Y

Nitroguanidine is an explosive which may be obtained URING the last deedesired quantity. While p r e from nitrogen of the air and limestone, and therefore is paring guanidine nitrate and a d e , i n t e r e s t in of potential interest from a technical standpoint. It is nitroguanidine by m e t h o d s g u a n i d i n e and subimportant scientifically, for from it aminoguanidine, described by Davis (8,10,29, stances closely related to it hydrazine, hydronitric acid, and possibly hitherto unhas been stimulated by the S 3 ) , a more complete knowlknown products, may be obtained by reduction. The work of Franklin (16) who edge of the reactions involved most satisfactory method for the preparation of nitroin these preparations seemed has classified t h e s e comguanidine is the nitration of guanidine nitrate with essential. This paper gives pounds as ammonocarbonic sulfuric acid, but the methods which have been prothe results of a detailed study acids. The diaryl- and triposed heretofore for preparing it yield products of of (1) the reaction between arylguanidines have been inquestionable purity. In the manufacture of explosives dicyandiamide and a m m o t ensiv e l y s t u d i e d because purity is an important factor, and since the purity of nium nitrate at temperatures they are among the m o s t nitroguanidine is directly dependent upon the purity of 150’ to 195’ C., and (2) widely used accelerators of of the guanidine nitrate used in its preparation, it has the nitration of g u a n i d i n e vulcanization of rubber (11, been necessary to develop a method for the preparation nitrate to nitroguanidine. 19). More recently the hyof pure guanidine nitrate. poglycemic and other pharHistorical Data In this investigation the optimum conditions for the macological properties of cerconversion of dicyandiamide to guanidine nitrate by FORMATION OF GUANIDINE tain substituted guanidines fusion with ammonium nitrate have been determined, -Guanidine was first ob(3, 6, 14, 15) have again diand guanidine nitrate in chemically pure form has tained bystrecker (6,235)as an rected the attention of chembeen isolated from this fusion product in amounts of oxidation product of guanine. ists to this class of substance. over 86 per cent of those calculated. The nitration of Thiele (24)and Volhardt (26) Of the many derivatives of pure guanidine nitrate has been accomplished with prepared guanidine thiocyathese substances, nitroguaniresulting yields of over 92 per cent of theory. nate by heating ammonium dine is of peculiar interest thiocyanate. I n 1920 both technically and scientifically. The compound is an explosive (9,25) and for this reason Werner and Bell (68)prepared guanidine thiocyanate by fusing a practical application may be found for it. Since it may be ammonium thiocyanate and dicyandiamide, but this method prepared from dicyandiamide, a derivative of lime-nitrogen recalls earlier work in which is recorded the formation of guani(calcium cyanamide), the raw materials are unlimited, being dine salts (21), as well as biguanide salts (1, d d ) , by the action essentially nitrogen of the air and limestone. The substance of ammonium salts on dicyandiamide. In addition, guanidine was the subject of a splendid and comprehensive investigation has been obtained from cyanamide and ammonium salts ( l a ) , by Thiele (24) in 1892, but for nearly thirty years following ammonia and phosgene ( 5 ) , and the treatment of orthocarthat time it received very little attention from chemists. bonk esters with ammonia (17). All of these modes of formaThis was probably owing to the rather tedious and uncertain tion may be correlated by considering guanidine an ammonomethods then available for the preparation of guanidine. carbonic acid, and they are either the ammoniation of another The present investigation had its inception in the desire to ammonocarbonic acid to guanidine, or the ammonolysis of a confirm Thiele’s observations on the formation of hydrazine mixed ammonoaquo- or ammonothiocarbonic acid to guaniand hydronitric acid from nitroguanidine, and to study in dine. The work of Werner and Bell (28) suggested to other indetail the reduction of nitroguanidine. Such a study was thought to offer interesting possibilities, since there was vestigators who worked independently the feasibility of apparently available now a simple and convenient method for obtaining other salts of guanidine directly from the respective the preparation of nitroguanidine in pure form and in any ammonium salt and dicyandiamide. This was advisable because the Werner and Bell reaction yields a product which 1 Received March 10, 1931. is difficult to purify owing to the presence of thio compounds 2 An abstract of parts of the theses submitted by 0. F. Steinbach, Jr., in June, 1927, and V. J. Sabetta in June, 1929, in partial fulfilment of the and to the deliquescence of guanidine thiocyanate. requirements for the degrees of master of science in chemistry and bachelor GUANIDINENITRATEFROM DICYANDIAMIDE-Ewan and of science in chemistry at the Polytechnic Institute of Brooklyn. PreYoung (IS) fused ammonium nitrate, sulfate, and chloride sented before the Chemistry Research Club of New York at the American with dicyandiamide a t temperatures of 150’ to 195’ C. and Museum of Natural History, New York,.N. Y., on February 16, 1931.

D

October, 1931

INDUSTRIAL AND ENGINEERING CHEMISTRY

obtained fair yields of the respective guanidine salt. Their work does not reveal the optimum conditions, and in explaining the mechanism of the reaction they assumed, as did Werner and Bell (28), the depolymerization of dicyandiamide to cyanamide and the subsequent ammoniation of cyanamide to guanidine. Davis (8, 29) and Blair and Brahani (4) working independently isolated an intermediate compound, the biguanide salt, and formulated a mechanism of the reaction by which cyanoguanidine is first ammoniated to biguanide and the latter in turn ammoniated to guanidine. Both have shown experimentally that biguanide salts may be ammoniated to guanidine. Davis, working a t 160" C., found that the main product a t this temperature was guanidine nitrate. He recommended a fusion for 2 hours, but observed no advantage when the materials were heated at 160" C. in an autoclave in either aqueous or alcoholic solutions. He reported yields of more than 85 per cent of the calculated amounts. r\TITROGuANIDINE-In 1892 Thiele (94) prepared nitroguanidine from guanidine nitrate and also from guanidine thiocyanate with nitric acid in fuming sulfuric acid. Thiele, and previously Pellizzari (9@, showed that the product obtained by Jousselin (18) by the action of nitric or sulfuric acid on guanidine nitrate was nitroguanidine and not nitrosoguanidine. Much later Ewan and Young (19)studied three methods for the preparation of nitroguanidine and concluded that the action of 92 to 98 per cent sulfuric acid on guanidine nitrate (1 cc. per gram of salt) for a period of 48 hours before dilution with water was the most satisfactory. High yields were obtained, however, with 87 to 95 per cent acid (2 cc. per gram of salt) after 30 minutes. They studied the effect of amount of acid, time of contact, and concentration of sulfuric acid on yield in reaching these conclusions. Davis (10, SO) has prepared a-nitroguanidine by the nitration 0.f guanidine nitrate with sulfuric acid. He used 5 cc. of acid (sp. gr. 1.84) to 4 grams of nitrate and allowed the mixture to stand 20 hours. He also prepared the p-nitroguanidine by nitrating the sulfuric acid-hydrolysis product of dicyandiamide.

nitrate with the subsequent formation of biguanide dinitrate and ammonia; (2) partial hydrolysis of dicyandiamide by moisture originally present in ammonium nitrate, yields guanidine, carbon dioxide, and ammonia, which products may condense to amelide (8); (3) dicyandiamide, ammonia, and carbon dioxide may be dehydrated to ammeline; and (4) the condensation of guanidine and dicyandiamide (28) or the polymerization of dicyandiamide (16) may yield melamine. From these considerations it is clear that the side reactions are quite complex, and the environment is by no means simple. The purity of the guanidine nitrate after recrystallization is questionable. Davis states (8) that the melting point of pure guanidine nitrate is 216" to 217' C. The product as obtained above melted a t 212" to 215' C. and Davis has reported products as low as 209" C. Note-These

reactions may be formulated as follows:

,NHz C=NH \N H. CSN (dicyandiamide)

8

The dicyandiamide used was obtained from the American Cyanamid

- LYiH

OJ

,NHt C=NH

+ NHiNOa

H 2: \NH*HNO,

/NHa C-NH \NH-CEN

4- 2H20

=

+

'NH NHI cLNH \NH*HNO~ (biguanide dinitrate)

(1)

+ COY + NHa

%d

(guanidine)

II

C

co

6>=",",

\NH,HNO~ (biguanide nitrate)

Experimental Procedure

PRELIMINARY STUDIES-The writings of Davis (8, 99) on the preparation of guanidine nitrate do not show why the temperature 160" C. has been chosen and why he believes it is advisable to continue the heating a t this temperature for a period of 2 or 3 hours. I n some of the preliminary experiments conducted by the authors, it has been found that if 2.2 molecular equivalents of ammonium nitrate and 1 molecular equivalent of dicyandiamidez are heated to 180' C., the mass will superheat to between 280" and 300" C. and, if cooled and held a t 180" C. for 1 hour, will yield 83 to 85 per cent guanidine nitrate, purification of the crude melt being effected by recrystallization from water a t 80" C. If an excess of 20 per cent ammonium nitrate is used, 89 to 90 per cent of guanidine nitrate may be recovered. A slight improvement in yield may be effected if half of the ammonium nitrate is fused separately and the mixture of dicyandiamide and remaining ammonium nitrate added dowly, each portion being allowed to react before more is added. There is a loss of ammonia during the reaction, and the crude melt is contaminated with an amorphous material which Davis has identified as a mixture of ammelide, ammeline, and melamine. The formation of these substances is attributable to four or more reactions which may occur under the conditions of the experiments: (1) biguanide nitrate first formed (4) is strongly basic and decomposes ammonium

1125

/I

/I

0 (ammelide)

(2)

0

H

Y

I/

(ammeline)

0

H

H

NH

I

H

(31

INDUSTRIAL AND ENGINEERING CHEMISTRY

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Vol. 23, No. 10

SOLUBILITIES OF GUANIDINENITRATEAND AMORPHOUS by fusion of dicyandiamide and ammonium nitrate, a series of MATERIAL-Accordingly it was considered necessary, in order experiments was conducted a t temperatures of 150°, 160°, to develop a method for the purification of guanidine nitrate, 170', 180°, and 195' C. Forty-two grams (0.5 mole) dito determine the solubilities of this substance and the amor- cyandiamide and 88 grams (1.1 moles) ammonium nitrate phous material in a few common solvents. Water, ethanol were heated together in an open beaker in an oil bath to the desired temperature (+ 2") for a period of 2 or 3 hours. In the last experiment the material in the beaker was brought to a temperature of 195' C. by direct heat from a Bunsen burner and a t first spontaneously superheated to 300" C., and was cooled and maintained a t 190" to 195' C. At intervals of '12 or 1 hour the material was weighed and samples of approximately 10 grams were withdrawn for examination. The samples were prepared by grinding to 80 mesh and were analyzed for guanidine and amorphous material. The results are tabulated in Table I11 and presented graphically in Figure 1. T a b l e 11-Purity of G u a n i d i n e Nitrate CRYSTALLIZA- CRYPTALLIZACRYSTALLIZATION 1 TION 2 TION 3 91.8 92.9 93 0 94.6 9s 0 99 3 Hot water 98.0 99 3 Hot water 98 6 99.8

SOLVENT Water, 80° C. Water. 20° C. Ethanol (hoiiine) Methanol (boiling)

T a b l e 111-Reparation of G u a n i d i n e N i t r a t e by F u s i o n of Dicyanamide a n d A m m o n i u m N i t r a t e INSOLUBLE CONVBRMATERIAL SION T O On basis GUANIDINE GUANIinn% NITRATE Loss DINE In guanidine TIME TEMP.IN FUSION IN WT. NITRATEfusion nitrate EXPT.

Figure 1-Effect of T e m p e r a t u r e a n d Durat i o n of F u s i o n u p o n Yieidu of G u a n i d i n e N i t r a t e a n d Insoluble M a t e r i a l

EIOlL7.S

(95 per cent), and methanol (95 per cent) were chosen. The guanidine nitrate used in these determinations was the crude reaction product crystallized from hot water and finally from water a t 20' C.; m. p. 213' C., purity 98.1 per cent by analysis as guanidine picrate, vide infra. The amorphous material was obtained by leaching large quantities of crude guanidine nitrate with water. The results are given in Table I. T a b l e I-Solubilities SOLVENT

of G u a n i d i n e N i t r a t e a n d A m o r p h o u s Material GUANIDINE NITRATE Temp. a

Water Water Ethanol Ethanol Methanol Methanol

C.

Grams/100 cc.

25.6 42.3 4.1 15.1 4.7 15.6

AMORPHOUS MATERIAL Temp. a C. Crams/lOO cc.

20 100 78

0.15 1.20 0.3

68

0.1

PURIFICATION O F GU~NIDINE NITRATE-From these data it is apparent that it is quite impossible to purify guanidine nitrate from the amorphous material by recrystallization from hot water, although this treatment does separate these substances from the unconverted ammonium nitrate and dicyandiamide. The following procedure is recommended to obtain chemically pure guanidine nitrate. The crude fusion melt (85 per cent guanidine nitrate) is recrystallized from boiling water slightly acid with nitric acid, the insoluble material being filtered from the hot solution, and guanidine nitrate recovered from the chilled solution. This product is dissolved in cold water, filtered, and evaporated to one-half its original volume and crystallized. A third recrystallization from boiling methanol yields pure guanidine nitrate, m. p. 217' C. (cor.). Numerous preparations have yielded a product which, by picrate analysis, showed a purity of 99.3 per cent to 99.8 per cent. Table I1 gives results indicating the efficiency of purification from the several solvents. EFFECTOF TEMPERATURE AND DURATION O F FUSION ON YIELDOF GUANIDINE NITRATEAND PRODUCTION OF AMORPHOUS MATERIAL-In the effort to establish definitely the uptimum conditions for the preparation of guanidine nitrate

1A

1

1c

2 3 1/a

1B 2A 2B 2c 20 2E 2 ~ 5

3A 3B 3c 3D 3E" 4A 48 4c 40 4Ea 5A 5B 5c 6A 6B"

1 s',1 2 3 31/4 l/z

1 ll/a 2 2'/4

1 11/z 2 21/4 1 l'/s 3 1

c. 150 150 150 160 160 160 160 190 200 170 170 170 170 200 180 is0 180

% 76.2 81.5 83.6 84.6 83.9 82.6 82.5 82.4 84.8 81.9 81.8 81.5 81.3 81.2 81.2 80.3 79.9 79.4 79.7 67.3 66 7 66.7 84.5 85.3 83.2 82.7

%

o

0

0 0 0

0 0 0

3.1 0

0 0 0

2.4 1.6

...

..

% 81.3 86.8 89.4 9Q.2 89.6 88.2 88.1 87.8 87.6 87.3 87 1 86.8 86.6 84.5 85.2 84.3 83.8 83.3 83.0

%

%

1.27 1.50 0.27 0.37 0.42 0.45 0.53 0.70 0.40 0.52 0.70 0.85 1.10 0.70 o 85 0.97 1.10 1.30 1.30 1 50 1.80 0.30 0.70 1.00 1.30

1.23 1.46 1.68 0.32 0.44 0 50 0.55 0.64 0.83 0.48 0.64 0.86 1.04 1.35 0.86 1.n~ 1.23 1.39 1.63 1.88 2.25 2 70 0.36 0.82 1 17 1.57

i.no

180 ... 200 2.4 195 4.1 68.8 105 68.2 195 4.6 6S.O 160 , 89.8 s',1 180 1.6 89.6 2 190 1.9 89.0 6Ca 21/( 200 3.1 85.5 60" " Heated for additional period at temperature indicated.

... ..

Analytical Methods AMORPHOUSMATERIAL-TWOgrams of the sample of the fused material were dissolved in 25 cc. of boiling methanol, and the insoluble material was filtered onto a tared Gooch crucible, washed with small portions of cold methanol, and weighed. QUALITATIVETEST FOR' BIGUANIDE-AmmoniaCal copper nitrate was added to an aqueous solution of the sample of the fused material. Rose-colored needles, insoluble in cold water and soluble in hot water to give a purple solution ( 8 ) , indicated the presence of biguanide. GUANIDINE-Guanidine was determined as guanidine picrate by a modification of the method developed by Vozarik ( 2 7 ) . The variations proposed by Blair and Braham ( 4 ) were taken into consideration, the method was subjected to a critical experimental review, and some variations in procedure have been introduced. Ammonium picrate "precipitating reagent" was prepared by dissolving 8 grams of ammonium picrate in water and adding 20 cc. of 15 M ammonium hydroxide; and since guanidine picrate is soluble to the extent of 1 part in 1280 parts of water a t 20" C. and 1 part in 13,000 parts of 0.8 per cent ammonium picrate solution a t 20" C. it was saturated with guapidine picrate by adding 0.5 gram of guanidine nitrate. The solution was diluted to 1 liter, shaken frequently for 2 hours, and allowed to stand for 24 hours to allow the excess guanidine picrate to settle out. This solution was also used to wash the precipitate of

October, 1931

INDUSTRIAL A N D ENGINEERING CHEMISTRY

guanidine picrate. Gooch crucibles prepared in the ordinary manner were finally washed with the precipitating reagent and dried a t 110" C. The authors have found, as have also Ewan and Young ( 1 3 ) , that guanidine picrate will adsorb 0.95 to 1.00 per cent of its weight when washed with precipitating reagent, and a correction must be applied for this. Ammonium hydroxide must be present in order to insure alkalinity of the final solution, since guanidine picrate is soluble in acid solution. The method developed is as follows: 0 5 gram of sample is dissolved in 5 to 10 cc. of water, and 250 cc. of precipitating reagent are added with constant stirring. The solution and precipitate are now allowed to stand for 6 to 12 hours a t 20" C., filtered on a tared Gooch crucible, washed with 50 cc. of precipitating reagent, dried a t 110" C., weighed, and 1 per cent of the weight of guanidine picrate [CN3Hb CeH20H(N02)3] deducted. Since the picrates of biguanide and guanylurea are somewhat insoluble, the purity of the guanidine picrate should be confirmed by a melting-point determination if these substances were present in the sample being examined.

These results indicate definitely and conclusively the optimum conditions for the conversion of dicyandiamide to guanidine nitrate by fusion n-ith ammonium nitrate. At temperatures below 150" C., the conversion of biguanide nitrate to guanidine nitrate is incomplete a t the end of three hours ( 4 ) , and a t 150" C. biguanide nitrate is present a t the end of 2 hours, but a t 160" C. or above, little biguanide can be detected a t any time during the reaction. It is evident that a t this temperature the formation of guanidine nitrate from biguanide nitrate is more rapid than the formation of biguanide nitrate from dicyandiamide. I t is probable that the large amount of amorphous material in the product of the fusion a t 150" C. is attributable to the presence of the strongly basic biguanide nitrate which produces ammonia. Temperatures much above 160" C. not only lead to decreased yields of guanidine nitrate, but also to the formation of larger amounts of amorphous materials, two factors which go hand in hand a t the higher temperatures. Experiments in the laboratory preparation of guanidine nitrate have quite conclusively demonstrated that the optimum temperature is slightly above 160" C.-i. e., 182" to 165" C. Moreover, it is not only useless to continue the fusion beyond l hour a t 160" C., but it is actually harmful, since it results in decreased yields of guanidine nitrate and, what is more serious, greater Contamination with amorphous material. It is well to point out that the temperature of fusion during the first hour is the most important factor in determining the yield of guanidine nitrate, and initial spontaneous superheating is very harmful. However, higher temperatures a t any time during the fusion bring about the formation of larger quantities of amorphous material.

1127

then dissolved in 3 liters of hot methanol, the insoluble material separated by filtration, and about 2 liters of methanol distilled off. The solution was cooled to room temperature, and the guanidine nitrate was separated. The yield was 315 grams, 86.5 per cent; the purity of product by picrate analysis, 99.5 per cent; m. p. 217" C.; insoluble material in original fused mass, 0.15 per cent. This procedure has been repeated many times in this laboratory and the above is typical of the results obtained. NITRATION (OR DEHYDRATION) O F GUANIDINE hTITR.4TE TO NITRoGuaNIDINE-Some preliminary experiments on the nitration of guanidine nitrate seemed to show that higher yields of the product were obtained if the nitration period were limited to 1 hour or less. Experiments have been conducted to verify this tentative conclusion and to give a more comprehensive knowledge of the reactions. Accordingly, 15-gram samples of guanidine nitrate ground to 80 mesh were added to 30 grams of sulfuric acid cooled to -10" C. or lower and allowed to react for ppriods varying from 10 minutes to 20 hours. The temperature of the reacting matcria!s was not allowed to rise above 0" C. during the nitration periods. At the end of these intervals the acid mixtures were diluted t o 300 cc. by pouring into ice and water. These experiments were concluded with the following observations: ( a ) conversion of guanidine nitrate (nitroguanidine precipitated plus nitroguanidine dissolved in the mother liquor) : ( b ) unconverted guanidine nitrate; (c) guanidine hydrolyzed during reaction; and ( d ) qualitative test for ammonia. The results of these experiments are given in Table IV and presented graphically in Figure 2. 6.0

30

4.0 30

20

/f

Laboratory Preparation of G u a n i d i n e N i t r a t e

On the basis of knowledge gained from the above studies, the following method for the preparation of pure guanidine nitrate was developed. Two hundred sixty-four grams (3.3 moles) of thoroughly dried ammonium nitrate, preheated to 110" C., were mixed with 63 grams (0.75 mole) of dicyandiamide, which had also been heated to 110" C. in a 600-cc. beaker and rapidly brought t o a temperature of 162' to 165" C. jn an oil bath. When the material had reached a temperature of 162" to 165" C., 63 grams more of dicyandiamide were added within hour a t such a rate as to prevent spontaneous superheating above 165" C. The fusion a t 162" to 165" C. was continued for a total period of 1 hour, and after the material had cooled to a partially solid mass, it was stirred vigorouqly to prevent caking. While still warm it was dissolved in 900 cc. of water a t 80" c. The insoluble material was filtered away, and 5 cc. of concentrated nitric acid were added. The solution was cooled rapidly to room temperature, the guanidine nitrate was separated by filtration, and second and third crops of crystals were recovered by evaporation of the mother liquor. This crude guanidine nitrate was

IN HOURS O f THE DEHYDRATION

I

5

IO

15

20

of Guanidine Nitrate with Concentrated Sulfuric Acid

Figure 2-Eehydration

Analytical Methods precipitated nitroguanidine was filtered immediately onto a tared Gooch crucible, washed with ice water, dried a t 110' C., and weighed. The nitroguanidine remaining in the solution of sulfuric acid was estimated by interpolation from the data given by Davis (7) for the solubility of nitroguanidine in solutions of sulfuric acid. UNCONVERTED GUANIDINE NITRATE-The combined mother liquor and wash water were treated while still cold with an excess of barium carbonate. The barium sulfate and barium carbonate were separated by filtration. The solution was now concentrated to 400 cc. and the small amount of barium carbonate which precipitated was removed; the solution was cooled and diluted to 500 cc. Aliquot portions of 200 cc. were taken, evaporated to 10 cc., and guanidine was determined as the picrate. GUANIDINE HYDROLYZED-The guanidine not accounted for as nitroguanidine and unconverted guanidine was considered to be hydrolyzed during the reaction. hTITROGUANIDINE-The

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INDUSTRIAL A N D ENGINEERING CHEMISTRY

AmowrA-Aliquot portions of 50 cc. were tested for ammonia with Nessler's reagent. Since a solution of pure nitroguanidine will develop the characteristic ammonia color with Nessler's reagent within '/z minute at room temperature, it was not possible to make a quantitative estimation of ammonia. The development of the ammonia color almost instantaneously was taken as evidence of free ammonia in the solution.

Vol. 23, No. 10

Further studies concerning the insoluble material, ita behavior with nitroguanidine, and its effect upon the purity of nitroguanidine, are in progress in this laboratory. DISCUSSION-A number of improvements in the method for the preparation of nitroguanidine are suggested by the experiments described. It is demonstrated here that if the nitration period is extended beyond 1 hour, no material Table IV-Nitration of Guanidine Nitrate t o Nitroguanidine CONVERadvantage is gained because hydrolysis then proceeds more S I O N 10 rapidly than the conversion of guanidine nitrate. The effect NITRA- YIELDOF NITRO- GUANIDINE GUANIDINE TION NITRO- G U A N I NITRATE NITRATE of this is to lower yields of nitroguanidine, and it is actually EXPT.P E R I O D G U A N I D I N E DINE UNCONVERTED HYDROLYZED harmful to continue the nitration as long as 6 to 20 hours. Hours Grams Gramsd % yo Gramsd Yo Maximum yields are obtained when the nitration period is 1N" '/a 9 . 8 0 3 7 6 . 6 81 7 2 . 7 5 9 1 8 . 3 9 f 0 . 0 2 5 + 0 . 2 3 2 ~ 5 11.507 9 0 . 0 9 3 . 1 0 . 7 4 8 4.99 +0.017 +o.io limited to l / Z to 1 hour. 35b 1 11.454 8 9 . 6 94 7 0 . 6 6 1 4.41 0,011 0.10 4Nc 3 11.446 89 4 9 4 . 5 0 . 6 0 9 4.06 0.163 1.27 The use of the crude guanidine nitrate fusion product for 5Nc 6 11.151 8 7 . 2 9 2 . 3 0 . 5 8 3 3.89 0.480 3.75 conversion to nitroguanidine is not permissible if reasonably 6Nc 12 10.986 8 5 . 9 9 1 . 0 0.582 3 . 8 8 0.847 5.06 7Kc 20 10.870 8 5 . 0 9 0 . 1 0.552 3 . 6 8 0.788 6.16 pure nitroguanidine is desired. The impurities introduced by Ammonia absent. the use of the crude product have not been estimated a t this b Ammonia present in traces. c Heavy tests of ammonia given. time. but it is quite certain that they are considerable in d As nitrozuanidine. amount. IMPURITIES INTRODUCED EY USEOF CRUDEFUSION PROD- Incidentally, qualitative experiments have shown that a oc.r-Davis ( 7 ) has suggested the utilizat,ion of the crude 50 per cent increase in the amount of sulfuric acid used would guanidine nitrate fusion product without purification for increase the yield of nitroguanidine. This would seem deconversion to nitroguanidine. This is a t variance with our sirable because it is easier to keep the temperature of the experience if pure nitroguanidine is desired. The fusion larger quantity of acid below 0" C. during the nitration product contains a t most 85 t o 87 per cent guanidine nitrate, period, and a larger percentage of the guanidine nitrate can and the remainder consists of excess ammonium nitrate, be converted to nitroguanidine. One further point in technic unconverted dicyandiamide, and amorphous material. The is important: The guanidine nitrate should be ground to 80 amorphous material, which may be obtained by leaching mesh or finer in order that there may be intimate contact large quantities of crude guanidine nitrate with cold water, between sulfuric acid and the salt. when mixed with ammonium nitrate and treated with sulfuric Laboratory Preparation of Nitroguanidine acid as in the preparation of nitroguanidine, was reprecipitatcd almost quantitatively on dilution to 10 per cent sulfuric One hundred fifty grams of concentrated sulfuric acid acid. When a mixture of 3 grams of dicyandiamide and 6 (sp. gr. 1.84) are chilled to -10" C. or lower, and 50 grams of grams of ammonium nitrate was added slowly to 10 cc. of this are reserved in a second beaker. Thirty-five grams of sulfuric acid chilled to -10" C. and the solution poured into guanidine nitrate are added slowly and with vigorous agita200 cc. of ice,water, a white material separated which was tion to the 100-gram portion of sulfuric acid, care being taken filtered, washed, dried at 110" C., and weighed. Yield 4.36 that the temperature does not rise above 0" C. This should grams, 3.90 grams. By using quantities ten times as large, require about 10 minutes. The reserved portion of sulfuric 48 grams of this material were obtained. acid is now combined with this mixture, and 15 grams addiThis is a white and granular material, practically insoluble tional guanidine nitrate are added as before within 5 minutes. in cold water, and does not melt below 300" C. It dissolves The mixture is maintained a t a temperature below 0" C. and with decomposition in boiling water, evolving a gas and giving stirred frequently for 30 minutes. At the end of this period a solution distinctly alkaline in reaction. The material is it is poured into 1 liter of ice and water, while the ice mixture soluble in cold concentrated hydrochloric acid and in 4 N is stirred vigorously, filtered immediately onto a Buchner, sodium hydroxide. It is slightly soluble in hot ethanol, but washed free from sulfuric acid with ice water, and dried at 110" C. The yield is 39 to 40 grams, 91.5 to 94.0 per cent. insoluble in cold ethanol. If 5 grams of this insoluble material and 10 grams of nitro- (Yields of 92 per cent have repeatedly been obtained by this guanidine are dissolved in boiling water, the insoluble ma- method.) If desired, this material may be recrystallized terial quickly decomposes as above. When the solution is from hot water without appreciably lowering the yield. cooled to room temperature, fern-clustered crystals are Conclusions obtained which do not resemble nitroguanidine. These (1) The maximum conversion of dicyandiamide and crystals are completely soluble in water. I n order to conform more nearly to t,he conditions existing in the preparation ammonium nitrate to guanidine nitrate by fusing these of nitroguanidine from the crude fusion product, 1 gram of the substances is accomplished by employing a temperature of insoluble material and 20 grams of nitroguanidine were dis- 162" to 165" C. for 1 hour. Temperatures higher or lower solved in 900 cc. of hot water. When this solution was and durations of fusion beyond 1 hour lead to decreased cooled slowly to room temperature, short white opaque yields of guanidine nitrate and greater contamination with needles were obtained. These are quite different from the amorphous material. long, clearly transparent, silky needles of pure nitroguanidine ( 2 ) Chemically pure guanidine nitrate may be separated which are obtained under the same conditions of recrystalli- from the crude fusion melt in amounts of 86 per cent of those zation. It appears probable indeed that a reaction occurs calculated by recrystallization, f i s t from water a t 80" C., and afterward from water at 20" C., or preferably from hot between the insoluble material and nitroguanidine. The above experiments are in agreement with our experi- methanol. ence in preparing nitroguanidine from the crude fusion prod(3) Pure guanidine nitrate melts a t 217" C. (cor.). (4) Guanidine nitrate uncontaminated with dicyanuct. When such nitroguanidine is recrystallized from hot water, it is more like glass wool than is nitroguanidine pre- diamide and amorphous material mq& be used to obtain pure pared from pure guanidine nitrate. Moreover, this "impure" nitroguanidine. (5) Nitration periods prolonged beyond to 1 hour nitroguanidine, it has been observed, differs from the pure form in the ease with which it is reduced in a neutral medium. result in decreased yield of nitroguanidine.

INDUSTRIAL A N D ENGINEERING CHEMISTRY

October, 1931

(6) A ratio of 3 parts by weight of sulfuric acid (sp. gr. 1.84) to 1 part of guanidine nitrate will give nitroguanidine in yields of 92 per cent. The temperature should be maintained below 0” during the nitration period, and the guanidine nitrate should be ground to a uniform fineness of 80 mesh. Acknowledgment

The authors wish to express their appreciation to Tenney L. Davis, of Massachusetts Institute of Technology, and K. R. Brown, director of the Research Laboratory of the Atlas Powder Company, for reviewing this manuscript and making valuable suggestions. The authors also wish to tjhank J. F. Kraus, of the Polytechnic Institute, who has checked the methods of preparation of guanidine nitrate and nitroguanidine described in this paper. Literature Cited (1) Bamberger and Dieckmann, Ber., 26, 543 (1892). (2) Bernthsen-Sudborough, “Textbook of Organic Chemistry,” p. 307, Van Nostrand, 1922. (3) Bischoff, Sahyum, and Long, J . B i d . Chem., 81, 325 (1929). (4) Blair and Braham, J . A m . Chem. SOL, 44, 2342 (1922).

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(5) Bouchardat, Compf. rend., 69, 961 (1869). (6) Braun, J . B i d . Chem., 81, 325 (1929). (7) Davis, J . A m . Chem. Soc., 43, 669 (1921). (8) Davis, I b i d . , 43, 2234 (1921). (9) Davis and Abrams, Proc. A m . Acad. Arts and Sciences, 61, 438 (1926). (10) Davis, Ashdown, and Couch, J. A m . Chem. Soc., 47, 1063 (1925). (11) Ellery and Powers, India Rubber World, 1 6 , 3 (1926). (12) Erlenmeyer, A n n . , 146, 253 (1868). 113) Ewan and Young, J . SOL.Chem. Ind., 40, 109T (1921). (14) Frank, Deut. med. Wochschr., 63, 1845 (1927). (15) Frank, Nothman, and Wagner, W i n . Wochschr., 6, 2100 (1926). (16) Franklin, J . A m . Chem. Soc., 44, 486 (1922). (17) Hofmann, A n n . , 139, 107 (1866). (18) Jousselin, ComDt. rend., 86, 648 (1877); 88, 814, 1084 (1879). (19) Naunton, J . Soc. Chem. I n d . , 44, 549T (1925). (20) Pellizzari, GQZS.chin.