0.5M NaBrO, were extracted for 3 minutes with equal-volume portions of 30 Aliquat 336-S-N03-xylene. The organic phases were then scrubbed once for 2 minutes with one-halfvolume portions of freshly-prepared 2M HN03-0.5M NaBr03 solution. Finally, the 14Ce tracer was stripped from the organic phases with equal-volume portions of 11M HC1 for 3 minutes. Results of the decontamination study (Table VI) indicate that berkelium, alkalies, alkaline earths, trivalent lanthanideactinide _elements,iron, zirconium, and niobium show negligible extractability. As would be predicted from their known abilities to form anionic nitrate species, UOz2+,NpOZ2+,and PuOz?+ ions show high solubilities in the organic phase-80, 99, 96%, respectively. These ions may be separated from cerium by stripping the cerium from the organic phase with
strong hydrochloric acid. Thus, 11M HCl easily reduces and strips the cerium; UOz2+,NPO,~+,and PuOz2+ions remain in the organic phase, inasmuch as their anionic chloro complexes are even more organic soluble than their anionic nitrate complexes. ACKNOWLEDGMENT
The author gratefully acknowledges the capable assistance of W. E. Bayless in the experimental work and of W. R. Laing for some of the analyses.
RECEIVED for review May 7, 1969. Accepted July 11, 1969. Research sponsored by the U.S. Atomic Energy Commission under contract with Union Carbide Corp.
Determination of Organic Isocyanates and lsothiocyanates in Dimethylformamide Joe A. Vinson‘ Chemistry Department, Shippensburg State College, Shippensburg, Pa. 17257
THEUSE of isocyanates and isothiocyanates as intermediates in polymer synthesis has prompted the appearance of many methods for their determination. The most widely used is the titrimetric method of Siggia and Hanna ( I ) in which excess n-butylamine is reacted with the compound in dioxane and the excess amine is titrated. The reaction is shown below using RNCO for isocyanates and RNCS for isothiocyanates.
+
n-C4H9NH? RNCO(S)
+
n-CdHgNHCO(S)NHR
(1)
This procedure has been adapted to the micro level by Karten and Ma (2). Chlorobenzene has also been used as the solvent in a micro method (3). Secondary amines such as di-nbutylamine (4, 5), piperidine (6), and diethylamine (7) have been used in various solvents. Polymeric polyisocyanate used in industry for the production of polyurethanes may be determined by an ASTM method (8). In this procedure toluene is the solvent and di-nbutylamine the reagent. After a reaction period of 1 hr, the excess amine is titrated potentiometrically. In spite of their simplicity, the titrimetric methods are often neglected because they are time consuming. For instance, Siggia’s method ( I ) requires 45 minutes at room temperature for aliphatic isocyanates and isothiocyanates. The present study concerns the attempt to shorten the reaction time by the use of dipolar aprotic solvents. 1 Present address, Department of Chemistry, Washington and Jefferson College, Washington, Pa. 15301.
(1) (2) (3) (4) (5) (6) (7) (8)
S . Siggia and J. G. Hanna, ANAL.CHEM., 20, 1084 (1948). B. S . Karten and T. S . Ma, Microchem. J., 3, 507 (1959). H. Roth, Mikrochim. Acta, 1958, 773. W. Siefken, Ann., 562, 99 (1949). A. G . Williamson, Analyst, 77, 372 (1952). H. E. Stagg, ibid.,71, 557 (1946). E. A. Navyashskaya, Khim.Prom., 1956,432. ASTM D 1638-67T, “Method of Testing Urethane Foam
EXPERIMENTAL
Solvent. Dimethylformamide (DMF), reagent grade, was stored over molecular sieves. Reagents. n-Butylamine, commercial grade, was distilled from barium oxide and stored over nitrogen in an amber bottle. Three grams of the amine were added to a 100-ml volumetric flask and diluted to the mark with DMF. Hydrochloric acid (0.1N) was standardized with potassium acid phthalate using phenolphthalein as the indicator. Organic isocyanates and isothiocyanates were commercially available samples distilled before use. Procedure. A 5-ml aliquot of n-butyl amine (approximately 2.5 mmole) is added to a 125-ml Erlenmeyer flask containing a Teflon stir bar and 10 ml of DMF. Approximately 1 mmole of isocyanate is weighed in a glass micro weighing bottle fitted with a glass stopper. The bottle is dropped into the flask so that the stopper separates from the bottle. The flask is corked and stirred for a few seconds until the solution is mixed. It is then left standing for 5 minutes at room temperature for aromatics and 10 minutes for aliphatics. Distilled water (50 ml) is added and the flask is cooled to room temperature with tap water or an ice bath. A few drops of methyl red solution are added and the
Table I. Determination of Isocyanates and Isothiocyanates in DMF Reaction time Compound (minutes) Reaction,’ 2 Allyl isothiocyanate 5 99.6 f 0 . 6 10 n-Butyl isocyanate 98.8 f 0 . 2 n-Butyl isothiocyanate 10 98.3 f 0 . 4 5 Phenyl isocyanate 99.1 f 0.1 Phenyl isothiocyanate 1 101.4 f 0 . 1 Naphthyl isocyanate 1 99.3 Z k 0 . 2 Naphthyl isothiocyanate 2 99.8 f 0 . 3 Tolylene 2,4diisocyanate 5 98.7 f 0 . 4 a Average value with standard deviation.
Raw Materials.”
VOL. 41, NO. 12, OCTOBER 1969
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Table 11. Determination of Polymeric Polyisocyanates
7, NCO Sample A B a
ASTM
DMF4
30.7 f 0.1 31.2 iZ 0 . 1 30.8 f 0.0
30.9 iZ 0 . 1 31.1 jZ 0.0 31.1 jZ 0.1
C Reaction time 5 minutes at room temperature.
solution is titrated to the pink end point with standard 0.1N hydrochloric acid. A blank is determined for the same reaction time used for the sample. DISCUSSION
Dipolar aprotic solvents seemed to be ideal for this reaction because dimethyl sulfoxide (DMSO) accelerates the rate of nucleophilic amine reactions (9). DMSO was tried as a solvent for the determination and was found to give high results, especially with aromatic isocyanates. DMF was found to be comparable to DMSO with respect to the rate of the reaction but failed to give high results, thus making it the solvent of choice. (9) M. Friedman, J. Amer. Chem. Soc., 89,4709 (1967).
Results for the determination of isocyanates and isothiocyanates in D M F are found in Table I. The average standard deviation was.0.3% for the compounds listed. Although a 250% excess of amine was usually used, quantitative results were obtained when a 100% excess of amine was present. The amine solution of D M F was fairly stable; the acid titre decreased slowly because of evaporation and oxidation of the amine. However, reagent stored for a period of one month gave satisfactory results. Polymeric polyisocyanates were determined using both the ASTM and the DMF methods. The results are shown in Table 11. The DMF method appears to give similar accuracy and precision with a significant reduction in reaction time; 5 minutes for DMF us. 1 hour for ASTM. ACKNOWLEDGMENT Samples of polymeric polyisocyanates were kindly supplied by Q. Quick of the Union Carbide Corp. RECEIVED for review October 10, 1968. Accepted May 29 1969. Presented at the Middle Atlantic Regional Meeting, Washington D. C., February 1969.
Electron Acceptor Complexes for Chromogenic Detection and Mass Spectrometric Identification of Phenol and Aniline Derivatives, Related Fungicides, and Metabolites Otto Hutzinger Atlantic Regional Laboratory, National Research Council of Canada, Halifax, Nova Scotia, Canada
ELECTRON ACCEPTORS form molecular complexes with many aromatic and “ T excessive” heterocyclic compounds. These complexes ( T - , donor-acceptor-, charge-transfer-, molecularcomplexes; molecular addition compounds) are usually intensely colored in the solid state and generally less soluble in organic solvents than their parent compounds. For these reasons electron acceptors have been used as spray reagents for the detection of certain compounds on chromatograms and for the isolation of compounds from reaction mixtures and their characterization. [For general references see (I).] Aromatic amino and hydroxy derivatives are particularly suitable for these procedures because electron releasing groups in the donor tend to increase color intensity and stability of the complexes. Some relevant examples with references to earlier work are given in (2-6). In this paper the color reactions of several electron acceptors with systematically substituted aniline and phenol derivatives, as well as some chemically related fungicides and fungicide metabolites, were studied. The properties of the 2,4,7trinitro-Pfluorenone complexes of two representative compounds, 3,5-dichloro-4-aminophenol(I) and 2,ddichloro-p0. Hutzinger, J . Chromatog., 40, 117 (1969). H. T. Gordon and M. J. Huraux, ANAL.CHEM., 31, 302 (1959). L. Fishbein, J. Chromatog., 22,480 (1966). F. Feigl, “Spot Tests in Organic Analysis,” Elsevier Publishing Co., Amsterdam, 1966. (5) G, F. Macke, J. Chromatog., 36, 537 (1968). 40, 2138 (1968). (6) J. H. Ross, ANAL.CHEM., (1) (2) (3) (4)
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ANALYTICAL CHEMISTRY
phenylenediamine (11), were more closely examined and the use of mass spectrometry for direct identification of compounds of this type in the complexed form was investigated. EXPERIMENTAL
Chemicals. 3,5-Dichloro-4-aminophenol(7) and 7,7,8,8tetracyanoquinodimethane (8) were prepared by literature methods; all other compounds were commercial samples purchased from the Aldrich, B.D.H., DuPont, Eastman, Fisher, K & K , Matheson Coleman & Bell, Nutritional Biochemical and Toms River Chemical companies. Spectra. The spectra were recorded on a Perkin-Elmer Model 521 spectrophotometer, a Beckman DK-2 spectrophotometer and a Varian A-60-A instrument. The mass spectral data were obtained with a Consolidated Electrodynamics Corp. 21-llOB instrument equipped with a controlled temperature probe for introduction of the sample directly into the source (9). Color Development. Hydroxy- and amino-compounds (20 pg) in methanolic or acetone solution were applied (spot diameter -5 mm) to Eastman Chromagram silica thin-layer sheets (6061) and sprayed with a solution (1 %) or the complexing reagent in chloroform or acetone. (7) H. H. Hodgson and J. S . Wignall, J . Chem. Soc., 131, 2216 (1927). (8) D. S . Acker and W. R. Hertler, J. Amer. Chem. SOC.,84, 3370 (1962). (9) W. D. Jamieson and F. G. Mason, submitted for publication
in Rev. Sci. Instr.
