ANALYTICAL CHEMISTRY
1032
Table 11. Performance of Constant-Voltage Circuit (Variation of output with time) Time, Hours Voltage 0 256.10 14 256.44 256.50 17 256.52 22 256.50 39
Co., 10.001-ohm) in series with the dummy resistor (Figure 3); the voltage drop was measured with a Leeds & Northrup Type K potentiometer. After an initial warm-up period of 30 minutes, readings were taken for a period of 1 hour a t 5-minute intervals (Table I). Short-range shifts about a mean position when the potentiometer is read continuously for a period of 1 minute were approximately 0.005% when the supply was connected directly to the power line and approximately O . O O l ~ owhen connected to a constant-voltage transformer. A 5 % change in line voltage caused an output change of 0.06%. Where line-voltage variations are severe, a constant-voltage transformer may be used. The constant-voltage performance was determined with the circuit of Figure 4, using a 120,000-ohm manganin-wire resistor for RA. The voltage drsp across a 30-ohm standard resistor
measured with a k e d s & Northrup student potentiometer was used in calculating the volt.age of the output. The resultsare given in Table 11. Adding a load of 90 ma. to the constant-voltage terminals of the supply (Figure 1) caused a change of 0.02’70in the output voltage. A 5% fluctuation in line voltage is followed by a 0.10 to 0.15% change in output voltage. LITERATURE CITED
,
Carson, W. N., Jr., ANAL.CHEM.,22, 1565 (1950). Cooke, W. D., and Furman. N. H., Ibid., 22,896 (1950). Elmore, W., and Sands, hl., “Electronics. Experimental Techniques,” pp. 39C-3, New York, McGraw-Hill Book Co., 1949. Farrington, P. S.,and Swift, E. H., ANAL.CHEM., 22, 889 (1950). Gittings, H. T., Atomic Energy Commission, Document AECD1908 (1948).
(6)
(7) (8) (9) (10) (11)
Greenwood, I. A., Holdam, J. V., and MacRae, D., “Electronic Instruments,” pp. 494, 501, 513, Kew York, McGraw-Hi11 Book Co., 1948. Lingane, J. J., ANAL.CHEM., 21, 497 (1949). Lingane, J. J., and Muller, R. H., Ibid., 20, 795 (1948). Minett, E. E., MacRae, D. .1.,and Townsend, J., Reu. Sci. Instruments, 20, 136 (1949). Oelsen, W., and Gobbels, P.. Stahl u. Eisen, 69, 33 (1949). Trishin, F. I., Zhur. anal. Khim., 3, 21 (1949).
RECEIVED October 14, 1950
Identification and Separation of Amines Employing Beta-Resorcylic Acid K. W. WILSON, FLOYD E. ANDERSON’,
AND
ROBERT W. DONOHOE
West Virginia University, Morgantown, W . Va.
T WAS observed that j3-resorcylic acid forms crystalline salts
1 with
certain amines. This reaction has been studied to discover which amines form salts and to determine whether these salts would be suitable derivatives for identification of amines. EXPERIMENTAL
Koppers j3-resorcylic acid was purified as described in “Organic Syntheses” ( 5 ) . This product was suspended in benzene and any residual moisture was removed by azeotropic distillation with benzene. The original Koppers product and the purified compound gave salts of equal purity. Most of the amines were Eastman products, R hich were dried over solid potassium hydroxide and used directly without further purification. The salts were prepared by dissolving 1.00 gram of p-resorcylic acid in 10 ml. of dry ether and adding the calculated amount of amine dropwise with shaking. Solid amines were dissolved in ether before adding. In most cases a crystalline salt formed immediately, but when an oil was produced it could be caused to cryEtallize by vigorous scratching with a metal spatula. When no visible reaction occurred, the mixture &as allowed to stand overnight to ensure ample time for salt formation and crystallization. The salt was then removed by filtration, washed with dry ether, and dried in air. The product was crystallized from ethyl acetate until a constant melting point was obtained. When the amine is pure, the salt separates in a high state of purity and requires no recrystallization. The salts are almost insoluble in ether and are obtained in about 80% yield. A11 reported decomposition points are corrected; they were taken in capillaries. The values represent, to the nearest degree, the temperatures a t which the last crystals disappeared. Slightly lower decomposition points were obtained using the Fisher melting point apparatus. The nitrogen analyses were done by the Kjeldahl method of Rlarcali and Rieman ( 4 ) . RESULTS AND DISCUSSION
The experimental results are summarized in Table I. The authors believe that these salts are not superior to the usual derivatives employed in the identification of primary and eecond1
Present address, Pyridine Carp., Yonkers, i X Y
ary amines; however, they should prove useful in the identification of tertiary amines. Accordingly, the table contains a relatively complete listing of common tertiary amines, but no attempt has been made to include all common primary and secondary amines. The decomposition points are dependent to a slight extent on the rate of heating; however, if the temperature rise is not greater than 5 ” per minute the compounds decompose within a 1 ” range. The melting points of the different salts lie fairly close together; however, nearly any amine can be satisfactorily identified if its boiling point is also known. The salts are almost nonhydroscopic, but they will absorb a little moisture if allowed to stand uncovered for several weeks. The melting point of a mixture of two salts shom in most cases a definite lowering from the melting points of the pure salts (Table I). The compounds are very easily prepared; a pure dry derivative can be made in less than 10 minutes. Aniline, ethylaniline, dimethylaniline, diethylaniline, otoluidine, p-toluidine, o-anisidine, 1-naphthylamine, and isoquinoline formed no salts under the conditions of the experiment. There is no sharp dividing line which separates these amines from those listed in the table. Apparently as the base strength of the amine decreases the salts become gradually more soluble in ether and decompose less sharply. Salts can be obtained from the above amines by mixing p-resorcylic acid and the amine, using no ether or only a small amount of ether; however, they do not decompose sharply and cannot be recrystallized. Using the base strengths of various amines as obtained by Felsing and Biggs (Z), Barron ( I ) , and Hall and Sprinkle ( 3 ) ,it appears that amines more strongly basic than pyridine will form salts under these experimental Conditions. (It is realized that base strengths measured in aqueous solution may not give an accurate comparison of base strengths in ether.) This generalization does not hold for two of the amines which were investigated; the weak base, quinoline, forms a salt, ~ h i l ediethylaniline, which is reported to be a considerably stronger base than pyridine (3), gives no salt. It would be difficult to predict with absolute
V O L U M E 23, NO. 7, J U L Y 1 9 5 1 Table I.
1033 The separation of quinoline and aniline encountered in the Skraup synthesis can be accomplished by this method.
Experimental Results M.P.
Amine Mono-n-propyl Mono-n-butyl Monoisoamyl Diethyl Di-n-propyl Diisobutyl Di-sec-butyl Di-n-butyl Diisoamyl Triethyl Tri-n-butyl Tribenmyl Pyridine a-Picoline ?-Picoline 2,4-Lutidine 2-Vin ylp yridine Quinoline Quinaldine 8-Quinolinol @-Diethylaminoethanol p-Anisidine p-Phenetidine Triethanolamine Di-o-tolylguanidine Mixture of diisobutyl and di-sec-butyl Mixture of triethyl a n d tri-nbutyl Mixture of pyridine and apicoline Mixture of mono-n-butyl and monoisoamyl After 4 recrystallizationq.
(Corr.) of @-Resorcylate 123 133 138 128 97 144 146 123 146 120 121 141 145 141 125 143 113 128 145 150 D1 _.
143
*-.
1x7
Oil 107-l15n
Formula of Salt CioHiaOiN CiiHiiOlN CizHigOiN CiiHirOiN CiaHziOiN CirHzaOiN CiaHzs04N CisHasOiN Cir HzsOiN CiaHziOiN CigHaaOiK CzaHwOiN CixHiiOiN CiaHiaOiN CisHiaOiN Ci4HisOdN CuHuOiN CiaHiaOiPi CiiHiaO4N CieHiaOaN Cia HioOaN Ci4HiaOsN CisHiiOaN
..... .,.,,
138-142
.. ...
103-108
.....
130-132
.... .
132-133
, ,, , ,
8 e & 6.57 6.17 5.82 6.17 5.49 4.95 4.95 4.95 4.49 5.49 4.12 3.17 6.01 5.67 5.67 5.36 5.40 4.95 4.72 4.68 5.16 4.88 4.65
.. ..
.. .. ..
%N
Found 6.60 6.10 5.83 6.28 5.39 4.93 4.93 4.91 4.30 5.46 4.24 3.19 5.78 5.78 5.54 5.41 5.49 5.11 4.88 4.53 5.18 4.91 4.56
..
.. .. .. ..
certainty whether or not a given amine would form a salt, but the correlation between base strength and salt formation seems to be applicable in most cases. SEPARATION OF MIXTURES OF AMINES
A mixture of 0.84 gram of quinoline and 0.66 gram of aniline was added to 2.00 grams of p-resorcylic acid in 15 ml. of ether. After standing overnight the quinoline p-resorcylate was removed by filtration, washed with a small amount of ether (the salt is slightly soluble in ether), and dried in air; 1.4 grams of quinoline 8-resorcylate were isolated, representing 78% recovery of quinoline. Aniline was recovered by evaporation of the ether from the filtrate after removal of the excess @-resorcylicacid. The acid was removed by washing with successive portions of sodium carbonate solution and drying over solid sodium hydroxide; 0.35 gram of aniline was recovered, representing 53% of the original amount. A mixture of 1.00 gram of pyridine and 1.00 gram of dimethylaniline was separated by treatment with 3.0 grams of @-resorcylic acid in 25 ml. of ether in a manner similar to that described above; 2.51 grams of pyridine 8-resorcylate were isolated, representing 85% recovery of pyridine. Recovery of dimethylaniline was practically quantitative. A mixture of 1.20 grams of tri-n-butylamine and 0.93 gram of 2-naphthylamine was separated by treatment with 2.0 grams of p-resorcylic acid in 15 ml. of ether as above; 1.5 grams of trin-butylamine 8-resorcylate were isolated, representing 68% recovery of the amine, and 0.85 gram (92%) of the 2-naphthylamine was recovered. The free amines can be regenerated from the 8-resorcylates simply by shaking the salt with sodium carbonate solution or sodium hydroxide solution. It seems probable that these salts might find use in isolation of amines from reaction mixtures as well as in separation of mixtures of amines. LITERATURE ClTED
Ranon, E. S. G., J . Bid. Chem., 1 2 1 , 3 1 3 (1937). (2) Felsing, W. A., and Biggs, B. S., J . Am. Chem. SOC.,55, 3624 (1)
(1933). (3) (4)
Hall, N. F., and Sprinkle. M. R., Ibid., 54, 3469 (1932). Marcali, Kalman, and Rieman, Wm., ANAL. CHEM.,18, 708 (1946).
The fact that 8-resorcylic acid does not form salts with most aromatic amines suggested that it might be used in the separation of mixtures of various amines.
(5) “Organic Syntheses,” Coll. Vol. 11, New York, p. 557, John
Wley & Sons, 1943. RECEIVED July 15, 1950.
Paper Chromatography of Volatile Acids E. P. KENNEDY’ AND H. A. B4RKER Division of Plant Biochemistry, University of California, Berkeley, Ca1;f. URING an investigation of the fatty acid metabolism of the bacterium Clostridzum kluyveri, it became necessary to identify and separate small amounts (1 to 2 micromoles) of volatile fatty acids ranging in chain length from 2 to 6 carbon atoms. The valuable method of Elsden ( 2 ) , based on chromatography of the fatty acid mixture on silica, could not be used because it requires considerably larger amounts of material. Therefore a paper chromatographic method was developed that would permit the separation and identification of fatty acids in micromole quantities. The separation of nonvolatile organic acids by chromatography on paper has been described by Lugg and Overell ( 6 ) ,but in this method the substances to be separated are applied to the paper as the free acids, a technique that obviously cannot be used FT ith volatile acids. The conversion of volatile acids to their nonvolatile hydroxamic acid derivatives by the method of Fink and Fink ( 8 ) is objectionable because it involves several additional steps. In the method described in this report, the volatile acids are applied to the paper as ammonium salts, and the chromatograms are developed in solvents containing free ammonia, 1 Present address, Biochemical Research Laboratory, XIassachusettGeneral Hospital, Boston, hlass.
so that the acids are present a t all times as the completely ionized ammonium salts. The location of the spots after development is accomplished by spraying the dried paper with bromophenol blue indicator, made acid nith a little citric acid. Since this method was v\orked out, two papers by Brown and Hall ( 1 ) and Hiscov and Berridge ( 4 ) have appeared, which describe the paper chromatography of volatile acids in ammoniabutanol mixtures. The method described below, while similar in principle, differ8 in important details and in the authors’ hands appears to offer some advantages. I n particular, the recommended indicator gives a more even background and sharply defined spots, th.e use of ammonium salts eliminates the intense and frequently confusing alkaline spots due to other cations, and the pretreatment of the paper with ovalic acid eliminates “ghost” spots. EXPERIMEYTAL
Whatman S o . 1 filter paper n a s used throughout the study
It was found necessary to wash the paper before use in order to avoid troublesome streaking and ghost spots. Good results were obtained nhen the paper nas thoroughly washed before use with 1% oxalic acid, then with copious amounts of distilled water, and finall\ dried at room temperature.
