Periodate Test for the Catechol and Hydroquinone Structeres OSCAR M. WlNDRATH Department of Chemistry, Niagara University, Niagara, N. Y.
Sodium periodate solution is used for the detection of the catechol structure in organic compounds. Results with selected structures are tabulated, the identity of the crystalline product from affirmative reactions is established, and a reason for the specificity postulated.
A
NEED arose in a structural investigation for a method of
determining the location of phenolic hydroxyl groups present in a complex molecule. Contradictory results had been obtained when various standard tests for the detection of vicinal dihydroxy groups were applied. The action of periodic acid on a molecule containing adjacent dihydric groups results in a fission a t this point \+ith t8heconversion of each carbinol group into a carbonyl group (3). I n an extension of this procedure to aromatic dihydric phenols, a method was devised which would impart limited oxidation ability to the periodate but still enable a reduction of the periodate group to be detected readily.
Table I.
Action of Sodium Metaperiodate on Selected Organic Compounds
Compound Rotenone Osajin Poiniferin Pomiferin trimethyl ether Quercitin Monn Catechol Resorcinol Hydroquinone 0 - , m - , and p-cresol Quinone Quinhydrone p-Ammophenol 0 - a n d p-phenylenediamine m-Phenylenediamine 1-Kanlithol Benzbic acid Gallic acid Blank
Sample Wt., G.
0.00985 0.01010
n.oiojo 0 . 0 1 155 0,00846 0 00846 0.00278 0 . no273
n ,00273
0.00270 0.00272 0 . on546 n ,00273 0.00272 0.00272 0.00360 0 0030.5 0.00470
Results
Color of S o h . Colorless Pale yellow Red Colorless Red, fading Did not dissolr Pale yellow Colorless Colorless Colorless Pale red Red-brown Naroon Red Red Colorless Colorless Tan Colorless
The addition of a 0.25.11 aqueous solution of sodium metaperiodate to the substance dissolved in methanol resulted in the formation of a crystalline precipitate within 0.5 hour. This precipitate could have resulted from the reaction of the periodate with any adjacent hydroxyl groups present; therefor?, the same procedure was applied to various other compounds known to contain this structure and to some which did not. Only those substances with a catechol or hydroquinone grouping in the molecule sho\ved a similar reaction. Of especial interest are the results obtained ivith osajin and pomiferin ( 5 ) , two complex isoflavones structurally similar, except that pomiferin possesses an additional hydroxyl adjacent to one already present in osajin. Pomiferin alone gave the characteristic positive test. No obvious mechanistic analogy can be made to the PIIalaprade reaction ( 3 ) since a nonvicinal diphenol, hydroquinone, gives a positive test. Probably the reaction involves other types of oxidation such as quinone formation or oxidative coupling. The presence of iodine in an oxidized state in the crystalline precipitate was established by its liberation on addition of sodium iodide and hydrochloric acid. A negative periodate test ( 2 ) and a positive iodate test (1)were obtained together with a flame
test for sodium. X-ray diffraction analysis gave identical patterns g-ith the precipitate and an authentic sample of sodium iodate, recrystallized from water. The specificity of this test apparently depends on the relative degree of solubility in methanol of the periodate and iodate salts; the less soluble iodate salts drop out of solution when formed. The lower oxidation potentials of o-dihydric phenols ( 4 )may offer an explanation for their preferential susceptibility to attack by periodate under the experimental conditions.
EXPERIMENTAL
An amount equal to 0.000025 mole of each of the compounds in Table I was dissolved in 10 ml. of dry methanol, then 0.00025 mole of sodium metaperiodate was added (1 ml. of 0.25M aqueous solution). The crystalline material m’aa deposited within 0.5 hour except with hydroquinone, %-here an additional time vas required. Under the same conditions, ethylene glycol and glycerol immediately deposited a white amorphous precipitate; D-glucose formed needles when the mixture nTas alloived to stand overnight. Occasionally, after the reagents had been mixed, a trace of amorphous material appeared in the solution. After removal by filtration the tests appeared normal. From a reaction vith catechol 7.5 mg. of crystalline precipitate TVJS collected. A theoretical yield of 9.7 mg. is indicated for an initial reaction between sodium periodate and catechol on a 2 to 1 basis. CONCLUSION
A simple, rapid, and accurate method has been developed Xvhich can be used for the detection of the catechol or hydroquinone structures in molecules of relatively high complexity. The use of small amounts of sample makes its application suitable as a tool for v-ork in the structure of naturalproducts. Its true value, hon ever, can be realized only when the test is used in conjunction TT-ith elemental analysis and functional group determination, because these procedures obviate consideration of similarly placed amino groups which give identical tests (see Table I). ACKNOWLEDGMENT
This work was initiated at The Ohio State University. The author is indebted to M. L. Wolfrom for valuable suggestions and to A h a Thompson for the x-ray diffraction patterns.
LITERATURE CITED
(1) FeigL F., “Spot Tests,” VOl. 1, 4th ed., P. 276, Elsevier, yew York, 1954. (2) Ibid., p. 278. (3) Jackson, E. L., “Organic Reactions,” vol. 11, p. 341, Wiley, New York, 1944. (4) Pennington, D. E., and Ritter, D. AI., J . Am. Chem. SOC.69, 187 (1947). ( 5 ) Wolfrom. RI. L., Harris, W. D., Johnson, G. F.,Moffett, S. AI., and Wildi, B., Ibid., 68, 406 (1946).
RECEIVED for review M a y
263
31, 1988.
Accepted September 23, 1955.
