LITERATURE CITED
Bamberger, E., Rust, E., Ber. 35, 46 (1902). Eegriwe, E., 2. anal. Chem. 110, 22 (1937). Feigl, F., “Spot Tests in Organic
bnalysis,” 5th ed., pp. 331, 334, Elsevier, New York, 1956. Be?. 32, 607 (4) Hantasch, A., Veith, -4., (1899j. (5) Johnson, K., Degering, E. F., J . Org. Chern. 8 , 10 (1943). (6) Lewin, L., Ber. 32, 3388 (1899).
( 7 ) Meyer, V., Ibid., 28, 202 (1895). (8) Michael, A , , J . prakt. Chem. 37, 507
(1888): (9) Nef, J. L’., Ann. 280, 263 (1894).
RECEIVED for review December 31, 1956. Accepted May 31, 1957.
Spot Tests for Nitromethane, Monochloro(bromo)acetic Acid, Dimet hy I S uIfate, Iodomet ha ne, and Methylsulfuric Acid FRITZ FEIGL and DAVID GOLDSTEIN laborat6rio da Produqtio Mineral, Ministirio da Agriculfura, Rio de Ianeiro, Brazil Translated by RALPH E. OESPER, Universify of Cincinnafi, Cincinnati, Ohio
b Nitromethane
condenses with 1,2naphthoquinone-4-sulfonic acid in alkaline solution to yield a blue-violet water-soluble p-quinoidal compound. The color reaction is specific for nitromethane within the group of nitroparaffins. The limit of detection is 0.6 y of nitromethane when the test is conducted as a spot test with calcium oxide as the OH- donor. Spot tests for monochloro(bromo)acetic acid, dimethyl sulfate, iodomethane, and methyl sulfuric acid can b e based on the fact that these compounds yield nitromethane on treatment with an aqueous solution of alkali nitrite. This product reacts directly in the reaction mixture with the sulfonic acid to give the characteristic blue-violet color, The limits of detection are: 5 y of monochloroacetic acid, 10 y of monobromoacetic acid, 50 y of dimethyl sulfate, 80 y of iodomethane, and 100 y of methylsulfuric acid.
I
studies of the reaction of 1.2-naphthoquinone-4-sulfonic acid (Ehrlich-Herter reagent) with organic compounds of rarious kinds, Sachs and Crareri (?) isolated. in addition to many other products, a yellow crystalline product of nitromethane. They observed that it dissolves in sodium hydroxide to give a blue color. The following successive reactions occur: N THEIR
O=O=CHNO,
+ NaOH
+
/--\
L.J
ONa I
This color reaction was mentioned incidentally by Turba, Haul, and Uhlen (10) in a paper dealing with the colorimetric determination of nitroparaffins. It has recently been made the basis of a specific colorimetric determination of nitromethane b y Jones and Riddick (4). Seemingly none of these workers knew of the previous work b y Sachs and Craveri. The color reaction with this reagent can serve for the sensitive spot test detection of nitromethane. By applying familiar methods of producing nitromethane from monochloroacetic acid, dimethylsulfate, iodomethane, or methylsulfuric acid, it has proved possible to tTork out spot tests for these compounds. \Then these tests are used, it should be noted-as was first pointed out by Ehrlich and Herter (1)-that 1,2-naphthoquinone-4-sulfonic acid is a sensitive reagent for compounds containing mobile XHL and CH2- groups. As such, it has also been recommended for spot test procedures ( 2 ) .
0
I/
+ 2 + 2XaOH
DETECTION OF NITROMETHANE
O = ~ S 0 3 ~ a
0 H 3 N 0
+
ONa
+ Na~S03+
2H20
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ANALYTICAL CHEMISTRY
Reactions 1 and 2, which are essential to the color test, can be accomplished in simple fashion and without increase in the reaction volume b y using calcium carbonate as the alkalizing agent. The reagent solution is a 0.5% aqueous solution of 1,2-naphthoquinone-4-sulfonic acid (sodium salt).
Procedure. T h e test is conducted i n a micro test tube. One drop of t h e alcoholic test solution is treated with a drop of t h e reagent solution and then several milligrams of calcium oxide are added. T h e mixture is shaken. Depending on t h e quantity of nitromethane present, a more or less intense blue or violet color appears. Limit of detection is 0.6 y of nitromethane. The procedure can be used to verify the presence of nitromethane in commercial nitroethane. DETECTION OF MONOCHLOROACETIC ACID
The classic method of preparing nitromethane rests on the reaction (8J 9 ) :
++
CH2C1COOH NaN02 + S a C l CH2r\’02COOH+. CHSSOz
+ COS
Accordingly, the presence of monochloroacetic acid can be shown indirectly through detection of the resulting nitromethane. Ordinarily, the nitromethane is recovered from the reaction mixture by steam distillation; the yield is around 35% (5). However, if the reaction is conducted in the presence of calcium oxide (to bind the nitromethane produced) a very satisfactory test for monochloroacetic acid results when the Ehrlich-Herter reagent is added. llonobromoacetic acid reacts analogously. It is highly probable that monoiodoacetic acid will react in the same manner. Procedure. A micro test tube is used. One drop of t h e aqueous test solution is treated with a n excess of calcium oxide and several milligrams of solid sodium nitrite. T h e mixture is kept in hot water for 2 to 3 minutes, then a drop or two of the reagent solution is added. The intensity of the re-
sulting blue or violet color depends on the quantity of monochloroacetic acid present. Limit of detection is 5 y of monochloroacetic acid and 10 y of monobromoacetic acid (3). The test is not reliable if methyl sulfuric acid or its salt is present. DETECTION OF DIMETHYL SULFATE OR IODOMETHANE
Kalden (11) observed that dimethyl sulfate reacts with a water solution of alkali nitrite: (CH,j,SO,
+ 2 S a N O2 CHXSO, + S:ISOI -+
Iotlomethane reacts analogously ( 6 ) CH3I
+ NaNOg
+
CHaX02
+ KaI
If these reactions are conducted in the prwence of calcium oxide, followed by t h ~Ehrlich-Herter reagent, milligram quantities of the methyl compounds are needed to give a positive response. Probably the calcium oxide partially saponifies the niethyl sulfate or iodide before the nitrite reacts. Consequently, it is best to warm the alcoholic test solution with the sodium nitrite and the reagent solution and then add the calcium oxide. Under these conditions, Condensation 1 probably occurs first and the addition of calcium oxide brings about rearrangement of the nitro compound to give the blue-violet salts or ions of the x i - form.
Procedure. A drop of t h e reagent solution a n d several milligrams of solid sodium nitrite are placed in a micro test t u b e and then a drop of t h e alcoholic test solution is added. The mixture is kept in a water bath (60’) for about 5 minutes. Several milligrams of calcium oxide are then introduced. U p to about 300 y of the methyl compound yields a blue color; smaller amounts give a violet shade. Limits of detection are 50 y of dimethyl sulfate and 80 y of iodomethane. The sensitivity is obviously much below that which might have been anticipated from the results of the tests for nitromethane and monochloroacetic acid. Probably there is concomitant formation of the isomeric niethyl nitrite (CH3K02),which does not react with the reagent. DETECTION OF METHYLSULFURICACID
As was anticipated, salts of methylsulfuric acid react with alkali nitrite t o give nitromethane.
+
K\‘nCH3SOI Ka?;Oz
-+
+ CHJYOz
S\‘n>SOd
Consequently, by combining this reaction with the test for nitromethane i t was possible to dewlop a rapid test for methylsulfuric acid and its salts. Correspondingly, salts of ethylsulfuric acid yield nitroethane, n hich does not respond to the Ehrlich-Herter reagent.
Therefore, the procedure described can be used t o distinguish between alkali salts of methylsulfuric and ethylsulfuric acids, if salts of monochloracetic acid are absent. Limit of detections; 100 y of methylsulfuric acid. ACKNOWLEDGMENT
The authors gratefully acknowledge the financial support of this study by the Conselho Nacional de Pesquisas. LITERATURE CITED
(1) Ehrlich, P., Herter, C., Z . phyaiol.
Chem. 4 1 , 379 (1904).
( 2 ) Feigl, F., “Spot Tests in Organic Analvsis,” 5th ed., p. 301, Else-
vier,New Tork, 1933.-
(3) Feigl, F., Moscovici, R., A n a l y s t
80.803 11955). (4)Jones, L. ’R., Riddick, J. A , , SAL. CHEW28, 1493 (1956). (5) Lieb, H., Schoeniger, TY., “Anleitung zur Darstellung organischer Praparate mit kleinen Substanzmengen,” p. G i , J. Springer, Vienna, 1956. Meyer, K., Stueber, O., Ber. 5 , 203 (1870’ I&]. Sachs , F., Craveri, M.,Ibid., 38, 3685 (1905). Ihid.. 41. 4457 (1908). Steinkc.mf. W.. Steinkopf; W.’, Kirbhhoff, G.,’ Ihzd., 42, 3439 (1909). Turba, F., Haul, R., Uhlen, G., 2. anqew. Chem. 61, 74 (,-1 qdq) -”,’ WZtlden, P . , Ber. 41, 445i (1908). RECEIVED for review December 21, 19%. Accepted M a y 31, 1957.
Micromethylatio n of Po Iysacc harides H. S. ISBELL, H. L. FRUSH, B. H. BRUCKNER, G. N. KOWKABANY, and G. WAMPLER Nafional Bureau of Standards, Washington 25,
b To provide a means for preparing carbon-1 4- or tritium-labeled ethers of polysaccharides, a micromethylation method has been developed. The procedure is based on the liquid ammonia macro method of Muskat. The methylation is conducted in an apparatus in which small measured quantities of an alkali metal are introduced into a closed system from a glass capillary previously filled with the molten metal. Measured portions of the capillary are cut off by means of a stopcock so arranged that liquid ammonia dropping from a reflux condenser dissolves the metal from the bore of the stopcock and transfers it to the reaction flask. Filter-Cel (diatomaceous earth) added to the reaction mixture disperses the polysaccharide
D. C.
and simplifies sampling and handling of the product. Other new techniques include use of dimethoxyethane as a solvent for methylation and formic acid for the hydrolysis of methylated dextran.
TECHXIQUES have been widely used in the determination of the structures of polysaccharides and other substances. The methylated material, after hydrolysis, yields methyl ethers which are then isolated and determined by suitable means. Conventional methylation procedures require large amounts of reagents and are not suitable for methylation with radioactive reagents because of the cost of the labeled materials.
ETHYLATION
The need for a semimicro method for the production of high-activity methyl ethers of polysaccharides, labeled with carbon-14 or tritium, led to the inrestigation of various methylation techniques. Jlacromethods employing liquid ammonia as a solvent have been found by others to be highly satisfactory (2, 4-7, 10). For use on a seniimicro scale, two methylation procedures have now been developed, based on the liquid ammonia methods of Muskat (5, 6). I n both procedures the carbohydrate in liquid ammonia is treated n i t h potassium or sodium in a closed system. I n one procedure the ammonia is then removed, and the carbohydrate salt is subsequently treated with an ewes? of methyl iodide. In the other VOL. 29, NO. 10, OCTOBER 1957
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