DECEMBER, 1937 (24) (25) (26) (27) (28) (29) (30) 131) . .
INDUSTRIAL AND ENGINEERING CHEMISTRY
Ibid., 25, 169 (1933). Ibid., 28, 1051 (1936). Hale, W. J., U. S. Patent 1,932,518 (1933). Hendricks, S. B., S. Am. Chem. SOC.,52, 3088 (1930). Herold, P., and Smeykal, K., U. S. Patent 2,068,132 (1937). Kauter, C. T., Ibid., 2,051,486 (1936). Kenner, J., and Parkin, M., J. Chem, SOC.,117, 882 (1920). Krase. H. J.. and Gaddv. V. L., S. Am. Chem. SOC.,52, 3088
(40) (41) (42) (43) (44)
(45) (46) (47)
(1930).
Lauter, W. M., U. 5. Patent 2,020,690 (1935). Martin, J., and Swallen, L. C., Ibid., 1,875,747 (1932). Mills, L. E., Ibid., 1,935,515 (1933). Mnookin, N. M., Ibid., 2,049,467 (1936). Nafash, M. S., Zbid., 2,075,825, 2,078,582 (1937). Nioodemus, O., and Schmidt, W., Ibid., 1,932,907 (1933). Zbid., 1,999,614 (1935). (39) Pray, H. B., Zbid., 2,063,191 (1936).
(32) (33) (34) (35) (36) (37) (38)
(48) (49)
1361
Sabatier, P., and Maihle, A., Compt. rend., 148, 898 (l9OQ). Saunders, K. H., U. S. Patent 1,911,717 (1933). Smeykal, K., Ibid., 2,043,965 (1936). Smolenski, E., Roczniki Chem., 1, 232 (1921). Swallen, L. C., U. S. Patent 1,875,775 (1932). Swallen. L. C., and Martin, J., Zbid., 1,926,691 (1933). Thomas, J., and Drescher, H. A. E., Zbid., 1,779,221 (1930). Thompson, J. G., Krase, H. J., and Gaddy, V. L., IND.EN& CHEM.,22, 735 (1930). Vorozhtzov, N. N., Jr., and Kobelev, V. A., S. Gsn. Chrm. (U. S. S. R.), 4, 310 (1934). Werner, “Chemistry of Urea,” New York, Longmans, Green and
Co., 1923. (60) Wickert, J. N., U. S. Patent 1,988,225 (1935).
RECEIVED September 8, 1937. Contribution 279 from the Industrial Farm Produots Research Division
Amination in Liquid Ammonia R. NORRIS SHREVE AND L. W. ROTHENBERGERI Purdue University, Lafayette, Ind.
As a result of the present comparatively low price for liquid ammonia and the fact that amines are increasing in industrial importance, a study is being made of the use of liquid ammonia as a solvent for the unit process of arnination. This paper reports some of the chemistry involved. The reaction of alkyl halides, including isoamyl chloride, isoamyl bromide, isoamyl iodide, n-hexyl bromide, and 2 - e t h y l b u t y l bromide u p o n sodium amide and potassium amide, suspended in liquid ammonia, has been studied. Yields of 50 to 60 per cent of isoamylamine have been obtained from isoamyl EBEAU in an early article (7) described the reaction between a liquid ammonia solution of sodium and alkyl halides. Methyl iodide gave methane, ethyl iodide gave ethane, and propyl iodide gave propane. Chablay (S), in a later and more extensive investigation of the same type of reaction, gave the reactions as: CtHJ CrHJ CzHJ
+ 2Na + NHI +CzHo + NaI + NaNHl + NaNHz +C2Hd + NaI + NHs
+ NaNHl-+-
+
C Z H ~ N H ~NaI
+Propyl iodide gave 71.4 per cent propane, 9.4 per cent propylene, and 21.2 per cent propylamine; isobutyl iodide yielded 69.8 per cent isobutane, 14.6 per cent isobutylene, and 15.6 per cent isobutylamine. Isobutyl chloride yielded only isobutane; isoamyl chloride yielded only isopentane; isoamyl iodide yielded isopentane, isoamylene, and isoamylamine. Chablay (9, 3) added alkyl halides gradually to suspensions of sodium amide in liquid ammonia at its normal boiling point. With methyl iodide the reaction was very vigorous and was said to lead to the formation of methylamine. The 1
Present address, Hercules Experiment Station, Wilmington, Del.
bromide and iodide, and 30 t o 40 per cent yields of isoamylamine from isoamyl chloride. With n-hexyl bromide 75 per cent yields of n-hexylamine have been obtained: 2-ethyl butyl bromide has given only about 10 per cent of 2-ethyl butylamine, along with 75 per cent yields of 2-ethylbutylene. These yields of amine are considerably higher than those reported in the literature for compounds of neighboring molecular weight. The fact that 50 up t o 75 per cent yields of amines have been obtained from isoamyl and n-hexyl halides points out that this method may be valuable for the preparation of certain amines. higher alkyl halides react with sodium amide to produce unsaturated hydrocarbons in amounts increasing with the molecular weight of the halide. Thus, ethylene was obtained in 5.4 per cent yield from ethyl iodide, propylene in 37 and 69.6 per cent yields from n-propyl iodide and n-propyl chloride, respectively, and isobutylene in 62.4 per cent yield from isobutyl iodide or in 83.6 per cent yield from isobutyl chloride. Picon (8), Bergstrom ( I ) , and White, Morrison, and Anderson (11) have also worked in this field.
Experimental Procedure Suspensions of sodium amide were made in liquid ammonia, using ferric nitrate as a catalyst, according to Vaughn, Vogt, and Nieuwland (IO), Franklin (4), and Kraus (8): A 500-ml. three-neck flask was fitted with a mechanical stirrer,
a dropping funnel, an air outlet through a drying tube containing soda lime, and a pentane thermometer with a range of -200’ t o +20” C. (Figure 1). The flask was cooled by means of a
solid carbon dioxide-alcohol bath. (For lower temperature, ether was used as the solvent.) Approximately 300 ml. of am-
1362
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 29, NO. 12
Analysis of Product I n every case the analysis was performed by distilling the dried ether extract through a Purdue modification of the Podbielniak column. The column consisted of a Pyrex glass reflux tube 8 mm. in diameter and approximately 110 em. long. The reflux tube contained a Nichrome wire in the form of a spiral which provided for intimate contact between downgoing liquid and upcoming vapor. A dead-air jacket was provided by means of another and larger Pyrex glass tube (diameter, 25 mm.) surrounding the reflux tube. Upon this second glass tube was wrapped a spiral of Nichrome resistance wire for maintaining the desired column temperature. A third and larger glass tube (diameter, 45 mm.) provided another air jacket around the heating coil. The column was equipped for regulation of reflux and was connected to a vacuum line in order to provide for distillation under r e duced pressure. The distillate was received in an inverted buret which allowed the quantity of distillate to be read to an accuracy of 0.1 ml. All compounds which boiled at temperaCourtesff, Monsanto Chemical CompanV tures much over 100" C. were distilled under AMINATIONCONTROL DEVICES reduced pressures. In order to determine the boilingpoint at standard pressure of such commonia were condensed in the 500-ml. flask, and 0.15 gram of pounds and thus the identity of the compound, the equation finely powdered ferric nitrate was added. With the stirrer rungiven by Hass and Newton (6) was used: ning slowly, one-half molecular equivalent of the metal to be used was added in small portions slowly enough to prevent a too 4 dt rapid rise in the temperature of the mixture. The mixture was 2'8808 - log a 273.1 t - 0.15 dt stirred slowly for 15 to 20 minutes after addition of the last of the metal or until the blue metallic color had completely dislog p = log of obappeared. The mixture was cooled to the desired temperature served presn by means of the solid carbon dioxide-alcohol bath. With the sure inmm. mixture a itated thoroughly, one-half molecular equivalent of of HP: alkyl halife was added from the dropping funnel at a rate that t = ob&zved would allow the temperature of the mixture to be maintained at b. p., C. the desired point. If the halide was added more rapidly than 30 9 = entropy of to 40 drops per minute, the temperature of the mixture rose so. vaporizarapidly that it could not be controlled by the cooling bath. The tion at 760 stirring and cooling were continued for about an hour after commm. pletion of halide addition. di = b. p. at.760 The ammonia was evaporated slowly (about 24 hours for mm. minus complete evaporation) by leaving the cooling bath around the 1, O c. reaction flask but not adding any more solid carbon dioxide. When the ammonia was all distilled, the contents of the reaction Figure 2 is a disflask was hydrolyzed by dropwise addition (at the start) of water; tillation curve for 150 ml. af water were added in all. The mixture was then t h e p r o d u c t of treated with 20 grams of sodium hydroxide to ensure the freeing of any amine present in the reaction product. Organic material reaction between was extracted from the mixture with three 75-ml. portions of ethyl sodium amide and ether. The ether extract was placed over solid sodium hydroxide isoamyl b r o m i d e to dry for about 15 hours in preparation for distillation. in liquid ammonia In runs where isoamylene was formed, this compound (boiling at 20.5" C.) passed out of the reaction flask during evaporation solution at -50 O of ammonia and hydrolysis of the reaction mixture. In order C. The c a l c u l a t o identify the isoamylene, the ammonia and other gases passing tion of the yield for from the reacbion flask were led through a condensing coil which each run was made was cooled by means of an alcohol-solid carbon dioxide bath at -10" to -20" C. The cooling coil terminated in a 200-ml. by use of a distillaround-bottom flask, its end dipping below the level of about 75 tion curve of this ml. of carbon tetrachloride contained in the flask. After comtype. The ether pletion of hydrolysis, the contents of the reaction flask was stirred was first distilled and warmed to about 30 C. in order t o drive over any remaining isoamylene. With the carbon tetrachloride solution maintained from the ether exat 0 " C., one-half equivalent of bromine, dissolved in 75 ml. of tract, and then a carbon tetrachloride, was added dr:pwise with shaking. The record was made of cooling bath was maintained at 0 C. for 2 hours and then millimeters of disgradually allowed t o rise to room temperature with frequent shaking. The contents of the flask was treated with sodium tillate us. boiling bicarbonate t o decompose excess bromine. The carbon tetratemperature as the chloride solution was washed with water and placed over product c a m e calcium chloride to dry. The solution was analyzed by disFIQURE 1. AMINATIONAPPARATUS over. tillation.
+
d
DECEMBER, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Use of Different Metallic Amides I n a preliminary investigation (in conjunction with A. R. Padgett), the difference in reaction of the amides of the four metals, sodium, potassium, barium, and calcium, with isoamyl bromide in liquid ammonia a t -34" C. was studied. The following table shows the results obtained (in per cent) : Metal Amide Na
K
Ba Ca
Isoamyl Bromide Recovered 0.0
Primary Amine 53.2 27.4
0.0 39.1 28.4
Secondary Amine 0.0
13.7 0.0 0.0
0.0 0.0
Total Amines 53 2 41.1 0.0 00
Sodium and potassium amides were much superior to barium and calcium amides for the preparation of amines. The low percentage of halide recovered in the barium and calcium runs was due t o the difficulty encountered in separating the reaction products. The difference in reaction between sodium and potassium is not a true indication, as shown in subsequent work where the reaction conditions were more closely regulated.
Effect of Variation in Reaction Temperature I n order to determine whether there was any difference in the ratio of amine and unsaturate with variation in reaction temperature, several runs were made a t temperatures ranging from -34" to -70" C. The alkyl halide used in this series of experiments was isoamyl bromide. The results are as follows: Reaotion Temp.
Metal
Monoamine
OC
-34 -34 -40 -40 -40 -60 -50 -70 -70
Na K Na Na K Na K Na K
Diamine
1363
is a noticeable increase in the proportion of diamine at the highest concentration.
Comparison of Chloride, Bromide, and Iodide Several runs were made under exactly similar conditions, except for the use of different isoamyl halides. The reactions were all carried out at - 50 O C. : Isoamyl Halide
Metal
c1 c1 c1 Bx Br I I
Diamine
%
%
75
37.8 43.1 30 7 33.6 54.3 53 0 55 0 47.5
0.0 0.0 3.9
10.0 9.2
Na Na
c1
Halide Recovered
Monoamine
3(
K Na
K
Na K
3.6 2.9 5.8 6 9 7.9
0.0 0 0 0 0 00 0 0 0 0
It seems significant that in the case of sodium amide and isoamyl chloride not all of the halide reacted. This wa$ borne out by the fact that the reaction did not proceed nearly as violently as with the bromide. Also some of the sodium amide remained unreacted as evidenced by the heat given off upon hydrolysis. The yield of amine with potassium amide and isoamyl chloride was much lower than that with sodium amide; however, no isoamyl chloride was recovered, indicating that the potassium amide tends to form unsaturates more readily than sodium amide in the case of reaction with isoamyl chloride.
Total Amines
%
%
%
50.0 48.8 50.0 48.5 48.5 54.3 53.0 56.1 53.5
2.0 2.1 3.9 5.9 4.0 2.9 5.8 3.9 3.8
52.0 50.9 53.9 54.4 52.5 57.2 58.8 60.0 57.3
Although there is not a wide variation in yield of amine over the temperature range, the yields a t temperatures below -50" C. are from 4 to 6 per cent greater than those a t temperatures above -50" C. This may be due t o loss of product by evaporation of ammonia a t temperatures nearer its normal boiling point.
Effect of Reactant Concentration in Solvent Sodium metal and isoamyl bromide were used in varying concentrations in liquid ammonia in order t o determine concentration effect. -All of the reactions were carried out at
-55"
c.:
Reactant per 100 Grams NHa Mole
Monoamine
Diamine
Total Amines
%
%
%
48.3 45.0 55.0 54.0 57.4 59.5
1.9 3.9 3.0 2.0 11.4 8.9
50.2 48.9 68.0 66.0 68.8 68.4
Probably the increased yield with higher concentrations was due to the higher ratio of reaction products present to the solvent ammonia; thus a smaller proportion of amine would be carried over with the evaporating ammonia. Vaughn, Hennion, Vogt, and Nieuwland (9)found that as high as 10 to 30 per cent of organic products of molecular weight comparable to the compounds obtained in this work were lost during evaporation of ammonia and hydrolysis after reaction. There
FIGURE 2. DISTILLATION C U R V E FOR THE PRODUCT OF REACTIONBETWEEN SODIUM AMIDE AND ISOAMYL BROMIDE~ IN LIQUID AMMONIA SOLUTION AT -50" C.
The reaction with metal amide and isoamyl bromide and iodide proceeded with a great deal more rapidity than with the isoamyl chloride. The iodide had more heat of reaction than the bromide but, as shown in the table, there was little difference in yield of amine whether the bromide or iodide was used.
Balance on Isoamyl Group An attempt was made to identify as nearly as possible the complete course of the reaction by identification of the isoamylene formed in the reaction. Several runs were made, using the procedure given for isoamylene determination. All were carried out with sodium amide and isoamyl bromide a t -55" C.: Run No, 1 2 3
Nonoamine
Diamine
%
%
MZ.
55.4 54.3
4.6 4.9 5.9
7.3 8.2 10.0
55.1
Isoamylene Total Dibromide Isoamylene Identified
% 11.0 12.4 16.1
74 71.0 71 6 76.1
INDUSTRIAL AND ENGINEERING CHEMISTHY
1364
Difference in Reaction of n-Hexyl and 2-Ethyl Butyl Bromides The best yield of amine in any runs was obtained from nhexyl bromide. The smallest yield of amine was obtained with 2-ethyl butyl bromide. All of the following reactions were carried out a t -55' C.: ?-Ethy! Butyl- ?-Ethylsmne butylene
Metal
n-Herylamine
%
%
%
%
Na
74.3 73.5 74.3 71.3
4.8 4.0
11.4 s.2 4.6 6.1
41.4 44.7 74.5 71.0
NB
I
