tion of phenols through the pyrolysis of the following aromatic compounds which contain oxygen in open or closed chains: phenoxyacetic acid, benzil, benzophcnone, acetophenone, phcnoxathiin, 9-xanthenol, phenylalanine, hippuric acid, phenylacetic acid, benzilmonoxime, ninhydrin, anthrone, diphenylmethylcarbinol, and 7,8-benzoflavone. USE OF PYROLYTIC SPLITTING OFF OF PHENOLS
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IN TESTING OF MATERIALS
Differentiation of Formaldehyde Plastics. Formaldehyde can be easily detected by the Eegriwe chromotropic acid reaction in plastics or resins prepared by the condensation of formaldehyde with urea, melamine, or phenols (4). A further differentiation is possible through the detection of pyrolytically split-off phenols by the indophenol reaction discussed above, as this test is characteristic for formaldehyde-phenol resins, such as Bakelite. Detection of Terylene and Dacron. Among the many synthetic fibers pro-
duced thus far, only Terylene and Dacron, which are polyesters of glycol and terephthalic acid (6), contain aromatic oxygen-containing components. Both of these fibers yield phenol when pyrolyzed and the latter is easily detected in the gas phase by the indophcnol reaction. A fraction of a milligram of specimen is adequate for this test. This finding is taken from a series of studies dealing with the application of spot tests to the investigation of synthetic fibers. Testing of Dyes Containing Phenol Groups. The detection of phenol components is of interest in the analysis of dyes. No rapid procedure has been available until now. Accordingly, milligram amounts of such dyes were subjected to dry heating and the gaseous pyrolysis products were tested by the indophenol reaction. A positive response was obtained from purely phenolic dyes such as alizarin, purpurin, hematoxylin, morin, curcumin, resorcylic acid, carminic acid, and aurintricarboxylic acid. As little as 50 to 100 y of any of these
dyestuffs exhibits a pyrolytic splitting off of phenol. On the other hand, azo dj'cs containing phenolic hydroxyl groups give a varied pattern when pyrolyzed. With some, the phenol reaction is distinctly weaker than that given by the purely phenolic dyes just noted, and with others no formation of phenol was observed. Therefore, the pyrolysis of such azo dyes apparently follows a course different from that taken by purely phenolic dyes. LITERATURE CITED
(1) Beilstein, C., “Handbuch der Organische Chemie,” Vol. VI, p. 112, 1923. (2) Boyland, E., Manson, E. D., Solomon, J. B., Wiltshire, G. H., Biochem. J. 53, 420 (1953). (3) Feigl, F., Amaral, J. R., Mikrochim. Acta 1958, 337. (4) Feigl, F., Hainberger, L., Chemist Analyst 44, 47 (1955). (5) Gibbs, H. D., J. Biol. Chcm. 72,
72(1927). (6) Heyn, A. N. J., “Fiber Microscopy,” Chap. 17, Interscience, New York, 1954.
Received for review May 14, Accepted September 23, 1959.
1958.
Spot Tests for Phenol Esters and Phenol Ethers FRITZ FEIGL and ERWIN JUNGREIS
Laboratorio da Producao Mineral, Ministerio da Agricultura, Rio de Janeiro, Brazil Translated by RALPH
E.
OESPER, University
Spot tests for phenol esters of carboxylic acids and for phenol alkyl ethers can be based on the fact that these types of compounds yield phenols when subjected at 150° C. to pyrolytic saponification and dealkylation, respectively. Oxalic acid dihydrate serves as the water donor in the saponification; the dealkylation is accomplished by the action of alkali iodide plus oxalic acid dihydrate. The resulting phenol volatilizes with the steam, and the vapor then gives the
indophenol color reaction with 2,6dichloroquinone 4 chloroimine. Triphenyl phosphate can be detected through pyroammonolysis to phenol by heating to 250° C. with guanidine carbonate. The detection limits are within the bounds of microanalysis. -
-
it
a
was
shown
paper (S), detected in the Ixthatprevious phenols can be
gas phase by the Gibbs indophenol re-
action. Accordingly, it was expected that tests for phenol esters and phenol alkyl ethers could be worked out if phenol vapors could be made to result
of Cincinnati, Cincinnati, Ohio from the saponification
or
dealkylation
of these esters and ethers. No tests are available for these classes of phenol derivatives at present. This objective can be reached through relatively simple procedures in which use is made of the reactivity of solid materials and topochemical reactions. when Hydrolytic cleavage occurs phenol esters are saponified:
R(Ar)COOAr + H20 —> R (Ar)COOH + ArOH As was reported previously (1,8), the hydrolytic cleavage of organic com-
pounds can be accomplished not only by the usual wet method (with participation in all cases of hydrogen and hydroxyl ions), but also by dry heating in the presence of organic or inorganic compounds which give off water at elevated temperatures. In fact, such thermal treatment sometimes accomplishes hydrolyses which proceed only slowly if at all by the wet method. In such pyrohydrolyses the active agent is the superheated steam derived from the hydrate (or water donor) at the elevated temperature and is released
in direct contact with the organic
com-
pound. Phenol esters of carboxylic acids are among the compounds susceptible to pyrohydrolysis. The dihydrate of oxalic acid can serve as the water donor; it starts to lose water at 102° C. and the dehydration continues in the molten oxalic acid up to 160° C. In this sintering or fusion the released water of crystallization brings about not only the hydrolysis of phenol esters but also provides water vapor which facilitates the volatilization of the phenols. Phenol esters of phosphoric acid (and probably of other noncarboxylic acids) do not undergo pyrohydrolysis when heated with hydrated oxalic acid. In contrast, heating with guanidine carbonate to 150° C. leads to the liberation of phenol, because under this condition guanidine carbonate loses ammonia which brings about the pyroammonolysis: OP(OC6H6),
+ 3NH3
—>
OP (NH2)3 + 3C6H5OH
Analogous reactions take place likewise with phenol esters of carboxylic VOL. 31, NO. 12, DECEMBER 1959
·
2101
acids.
in
a micro test tube. Small amounts of the sample or 1 drop of its solution in alcohol are mixed with about 1 eg. of oxalic acid dihydrate, after taking the mixture to dryness if necessary. The test tube is then placed in a glycerol bath that has been preheated to 150° C., and the mouth of the test tube is covered with a disk of freshly prepared reagent paper. After 1 to 2 minutes, the paper is held over concentrated ammonium hydroxide. A positive response is indicated by the development of a blue stain, whose intensity is a measure of the quantity of phenol ester present. The color of the spot either quickly fades to a dirty violet or disappears entirely. Renewed exposure to ammonia will restore the blue color. Reagent Paper. The filter paper is bathed in a saturated benzene solution of 2,6-dichloroquinone-4-chloro-
As ammonia is released along
with phenol, the contact of these two compounds with 2,6-dichloroquinone-4chloroimine will result in the blue coloration that is characteristic of the Gibbs reaction. Phenol alkyl ethers are known to lose their alkyl groups when warmed with concentrated hydriodic acid: Ar—O—R + HI
—>
ArOH + R.I
Nascent hydriodic acid is used in the present test for this dealkylation—-i.e., the phenol ethers are heated with a mixture of potassium iodide and hydrated oxalic acid. The latter releases hydrogen iodide which, as a gas, reaches the phenol ether and they enter into the above reaction. As in the saponification of phenol esters, the steam set free from the oxalic acid dihydrate aids in volatilizing the phenols. The pyrohydrolysis of phenol esters by means of oxalic acid and the dealkylation of phenol ethers with alkali iodide and oxalic acid are readily accomplished at 150° C. These effects as well as the pyroammonolysis of triphenyl phosphate, when combined with the indophenol reaction of the liberated phenols, lead to satisfactory tests for phenol esters and ethers that can be carried out readily within the bounds of spot test analysis.
DETECTION OF PHENOL-ALKYL ETHERS
Procedure. A little of the sample a drop or two of its solution in ordinary ether is placed in a micro test tube along with about 1 eg. of the reagent mixture. After taking to dryness if necessary, the test tube is closed with a disk of reagent paper and heated in a glycerol bath to 150° C. After several minutes’ heating, the paper is exposed to ammonia vapors. A blue stain indicates a positive response. Reagent Mixture. Equal weights of pulverized potassium iodide and oxalic acid dihydrate are mixed shortly before the test The test revealed 0.5 y of veratrole, or
imine.
The test revealed 10 to 20 of the following compounds: phenyl acetate, phenyl benzoate, phenyl anthranilate, diphenyl carbonate, phenyl salicylate, and phenyl stearate. DETECTION OF TRIPHENYL PHOSPHATE
Small amounts of the drop of its solution are mixed in a micro test tube with several centigrams of guanidine carbonate and evaporated to dryness if necessary. The test tube is placed in a glycerol bath previously heated to 120° C. and the mouth of the tube is covered with a disk of freshly prepared reagent paper. The temperature of the bath is then increased to
Procedure.
sample
DETECTION OF PHENOL ESTERS OF CARBOXYLIC ACIDS
Procedure.
250° C. A positive response is indicated by the appearance of a blue stain on the paper. The limit of identification is 5 of triphenyl phosphate.
The test is conducted
or
1.0 7 of phenetole, 2.0 y of isoeugenol, 25 7 of anethole, 10 y of phenoxyacetic acid, 20 7 of ?n-phenetidine, 10 y of ,/3-diphenoxyethane, 10 y of ethoxyphenoxyacetic acid, 2.5 y of p-dimethoxybenzene, 5 7 of o-methoxybenzoic acid, 10 7 of a,7-diphenoxypropane, and 2.5 7 of guiacol benzoate.
a
LITERATURE CITED
(1) Feigl, F., Angew. Chem. 70, 166 (1958). (2) Feigl, F., Haguenauer, D., Jungreis, E., Talanta 1, 80 (1958). (3) Feigl, F., Jungreis, E., Anal. Chem. 31, 2099 (1959).
Received for review
May
14,
Accepted September 23, 1959.
SCIENTIFIC COMMUNICATIONS Separation of Boron from Alloys and Other Materials by Pyrohydrolysis Sir: It has been found possible to separate boron from metals and alloys such as zirconium, Zircaloy, Zircaloybase uranium alloys, stainless steels, and other materials such as boron carbide by pyrohydrolysis. The method which follows has been applied to the determination of boron in the above materials as well as to the separation of boron in a pure form from various matrices for isotopic analysis of the element. The method is adaptable to remote operation and should prove useful in isolating boron from radioactive matrices whose level of activity complicates the direct application of boron color reagents or conventional methods of separation. Pyrohydrolysis Apparatus. Nickel tube, 34 inches long, 13/h inch in inside diameter, l1/is inches in outside
2102
·
ANALYTICAL CHEMISTRY
Table
I.
Determination of Boron in Various Materials
(Analysis by mannitol titration
or
spectrophotometrically with quinalizarin) Boron Present, %
Type of Material Boron-stainless steel alloy Boron carbide technical grade
1.27 67.1
Boron carbide high purity
76.2 76.7 P.P.M.
Boron carbide sintered disks Zircaloy-base uranium alloy Zircaloy-base uranium alloy Boron carbide-uranium dioxide mixture
303 303 168
Boron-uranium dioxide mixture
500
0
b
Single analysis. Samples pyrohydrolyzed at
13UUV
