components were separated according to the procedure previously described. The tetrachlorophenols were separated by the gradient elution technique. However, once the tetrachlorophenols had been removed, the gradient elution was terminated and the pentachlorophenol was desorbed with 100 ml. of glacial acetic acid. Otherwise a n extremely large volume of solution would have been required to desorb the pentachlorophenol. A 10-ml. aliquot of the pentachlorophenol fraction mas diluted t o 100 ml. with methanol. The absorption of each component was measured at the appropriate wave length (Table I). using a corresponding concentration of glacial acetic acid in methanol as the reference. From the respective measured volumes and absorptivities the concentrations of the components were calculated. Table I1 summarizes the analyses of the knon-n mixtures. Pentachlorophenol may be determined t o =!=0.5y0 in the 100-mg. range, whereas the tetrachlorophenols may be determined to = t O . l mg. in milligram amounts. The principal impurity or lower rhlorinated phenol present in commercial pentachlorophenol products appears to be 2,3,4,6-tetrachlorophenol.However the presence of lesser amounts of other chlorophenols requires that the separation be made under conditions t h a t n ill give maximum resolution. One hundred milligrams of the commercial material is placed on the resin after having first been neutralized with sodium hydroxide-methanol solution. The separation is then made according to the procedure described in the previous paragraph. Tiessens (6, 7) has prepared and measured the ionization constants of numerous chlorophenols. His results indicate t h a t chlorine in the ortho position enhances the acidity to a greater extent than chlorine in the meta and para position. The ionization constants reported for penta and tetra-
Table
I.
Ultraviolet Absorption Data for Pentachlorophenol and Tetrachlorophenols in Methanol a t 25' C.
Rave Length of Maximum Molar Absorptivity Absorption, Mp Compound Phenol Phenate Phenol Phenate 2870 4570 300 317 2,3,4,5-Tetrachlorophenol 2910 5570 300 320 2,3,4,6-Tetrachlorophenol 2240 6100 294" 310 2,3,5,6-Tetrachlorophenol 2870 5310 303 323 Pentachlorophenol a 2,3,5,6-Tetrachlorophenolhas a second absorption maximum a t 286 m p .
Table
(I.
Analysis of Known Mixtures of Pentachlorophenol and the Isomers of Tetrachlorophenol
Mixture 1 2 3 4 5
Added Found Added Found Added Found Added Found Added Found
2,3,4,5Tetra, Mg. 4.00 4.03
...
...
4.00 4.04
... ... ... ...
chlorophenols, with the exception of the 2,3,4,5-tetraisomer, show very small differences. The separation technique described should also be applicable t o t h e separation of other negatively substituted phenols and weak acids having p K values in the approximate range of three t o nine. The concentration of acetic acid in methanol to be used for the gradient elution is chosen on the basis of a n elution with a fixed concentration of acetic acid in methanol. If a given fixed concentration separates most of the minor components from the major component or vice versa in a volume of 100 t o 150 ml., one half of that concentration is used for the gradient elution. This generalization should be
2,3,4,6Tetra, Mg. 4.20 4.22 4.20 4.23 4.20 4.03 4.20 4.34
...
2>3,5J6-
Tetra, Mg. 4.00 3.95 4.00 3.97 4.00 3.95
Penta, Mg. 69.7 69.5 81.7 81.7
...
73.4 72.8 91.0 91.3
... ...
...
...
...
...
used as only a guide, for the optimum concentration must be det,ermined experimentally. LITERATURE CITED
(1) Bushch, H., Hurlbert, R. B., Potter,
V. R., J . Biol. Chem. 196, 717 (1952). (2) Logie, D.,Analyst 82, 563 (1957). (3) Plapp, F. W.,Casida, J. E., ANAL. CHEM.30,1622(1958). (4) Seki, T., J. Chromatog. 4, 6-10 (1960). (5) Shelley, R. N., Umberger, C. J., ANAL. CHEM. 31,593 (1959). (6) Tiessens, G. J., Rec. trav. chim. 48, 1066 (1929). (7)Ibid., 50, 112 (1931). RECEIVEDfor review June 30, 1960. Accepted October 27, 1960 ACS Meeting in Miniature, Detroit, Mich February 1960.
Detection of Ketones via Oxidation to Esters RUBIN DRUCKERI and MILTON J. ROSEN Department of Chemistry, Brooklyn College, Brooklyn, N. Y.
b Ketones may b e detected and distinguished from saturated aliphatic aldehydes by oxidation with peroxytrifluoroacetic acid, which produces esters or lactones only with the former. The resulting esters or lactones may b e detected by the characteristic purplered color of the ferric hydroxamate test.
N
TESTS for the detection of the carbonyl group in aldehydes and ketones have been recorded in the chemical literature, but a reliable test which will give positive results only with ketones has been lacking. Ketone tests that have been reported are not of sufficient selectivity in distinguishing between aldehydes and
UMEROUS
ketones to be used as general classification tests. This work is concerned with development of a ketone test based on the peroxytrifluoraocetic acid oxidation of ketones to esters and/or lactones
1 present address, ~ i ~ , , rnc,, ~ , N~~ York, N. Y .
VOL 33, NO. 2, FEBRUARY 1961
273
Table I.
Results of Hydroxamic Acid Test (HAT) on Various Types of Compounds after Oxidation with Peroxytrifluoroacetic Acid
Class Ketones
Compound Methyl isoamyl ketone Diisobutyl ketone lcetophenone Benzophenone
Results
Cyclohesanone
E 8
C17H3S C16H33 CiiHz, C d z i Benzyl methyl ketone p , p '-Dichlorobenzophenone Benzil m-Nitro acetophenone Benzoin Methyl ethyl ketone Acetone Aldehydes
Heptaldehyde Salicylaldehyde Propionaldehyde Acetaldehyde Paraformaldehyde m-Nitrobenzaldehyde Isobutyraldehyde Isovaleraldehyde Benzaldehyde Anisaldehyde p-Dimet hylsminobenzaldehyde p-Chlorobenzaldehyde Crotonaldehyde Cinnamaldehyde
Alcohols and phenols
Cyclohexyl alcohol 3-Methylcyclohexano1 sec-Butyl alcohol n-Butyl alcohol Phenol 1-Phenylpropanol Allyl alcohol Ethylene glycol Propylene glycol 2,3-Butylene glycol 2-Amino-2methyl-3-pentanol
+ +
++
' + ++ + ++ +
+ CFaCOOOH II
-
-
274
ANALYTICAL CHEMISTRY
Amine8
-
Olefins and unsaturated compounds
-
Hydrocarbons and ethers -
++ + + ++ + +
Oximes
+ + + +
Miscellaneous compounds
(1)
-
R'COOR 4-"200
R'bNHO-
NHO-
J
+ CFSCOOH
Amides
-
0
R'--COR
Carboxylic acids
+
(8) and detection of the resulting esters and/or lactones by the Fell-known ferric hydroxamate test (4).
R'
ReCompound sults 2-Methyl-2,4pentanediol Phloroglucinol Resorcinol 2-Nitro-2-methyl- 3-pentanol Cinnamic acid Acetic acid Benzoic acid Caproic acid Lactic acid Acetanilide Benzsmide Acetamide A'-Methylacetamide X,N-Dimethylacetamide Aniline Dimethyl " ' aniline n-Butylamine Diethylamine Tributylamine Styrene a-Methylstyrene Indene Cyclohexene 2-Octene Benzene Naphthalene Anthracene Diphenylmethane Ethylbenzene Diisopropyl ether Di-n-butyl ether Dibenzyl ether Hexane Acetone oxime Heptaldoxime 4Cyclphexanone oxime l-Phenyl-1hydroxyprppanone oxime 1-o-Methoxyphenyl pr?panone oxime p-rvlethylacetophenone oxime Anthraquinone Fructose Glucose sec-Butyl iodide n-Butyl bromide 2-Nitrobutane p-sitrophenylacetonitrile Propionitrile
Class
+ H30+
+ ROH
J
(2)
8
3R' --SHOH
+ FeC13
e
J
(R' -KHO)sFe
+ 3HCl
Peroxyacetic acid ( 7 ) , peroxybenzoic acid (6, 11, l a ) , and Caro's acid (H2S06) (1-3) have also been used to effect this oxidation, but peroxytrifluoroacetic acid was chosen because it is more efficient and gives good results m-ith dialkyl ketones, alkylaryl ketones. and diary1 ketones ( 8 ) . Peroxytrifluoroacetic acid is also the basis for the quantitative determination of some lon-er alkyl ketones ( I S ) . EXPERIMENTAL
Oxidation Procedure. I n a 4-inch test tube, place 1 ml. of methylene chloride and 0.05 ml. (1 drop) of 90% hydrogen perovide (Becco Chemical Division, Food Machinery and Chemical Corp., Buffalo, x. Y.). (C.4UTION: Store t h e peroxide in a cool place in vented bottles which are protected by metal cans. Keep from contact with metal salts and dirt. Wear protective rubber gloves and face mask when handling. Flood with water if allowed to come in contact with skin or clothing.) While cooling in a n icewater bath, add 0.3 ml. (6 drops) of trifluoroacetic anhydride (Distillation Products Division, Eastman Organic Chemicals, Rochester. K, Y.), and agitate gently for about 30 seconds until all the 90% H202has reacted and the mixture is homogeneous. Add the methylene chloride solution of the peroxyacid to 0.2 ml. (0.2 gram) of the sample dissolved in 2 ml. of methylene chloride in an 8-inch test tube, attach a finger condenser, and reflux for 5 minutes on a steam bath. Cool the reaction tube and pour its contents, with stirring, into a small beaker containing 10 ml. of 0.5M sodium carbonate. Transfer the mixture to a 30-ml. separatory funnel and shake for 2 minutes. Separate and transfer the methylene chloride lower layer to another 30-ml. separatory funnel. Wash it once with another 10-ml. portion of 0.5M sodium carbonate solution. Then wash i t twice with 10 ml. of 10% sodium bisulfite solution, and finally once with 10 ml. of water. Evaporate the methylene chloride on a steam bath and perform the hydroxamic acid test below, on the residue. Hydroxamic Acid Test (HAT) ( 5 ) . Dissolve the residue in 1 ml. of 1M hydroxylammonium chloride reagent. (Dissolve 70 grams of hydroxylamine hydrochloride, 0.2 gram of thymolphthalein, and 0.1 gram of methyl yellow in 1 liter of methanol.) Add 2M methanolic potassium hydroxide (to about 1 liter of methanol in a 2liter volumetric flask, add 264 grams of 85% KOH, cool, and dilute with methanol to 2 liters; cool and decant the clear liquid) until the mixture just turns blue, and add 0.5 ml. more. Boil for 30 seconds, cool, and add 2 V methanolic
hydrochloric acid (add 169 ml. of 36% HC1 to 832 ml. of methanol) until a pink color is just formed. Add two drops of 10% ferric chloride. A positive test is indicated by a red-purple color, a negative test by a yellow. DISCUSSION AND RESULTS
Results of the test are given in Table 1. Since this test depends upon the oxidation of a ketone to an ester, this test is valid only if esters are absent from the sample before the oxidation. Every ketone tested gave positive results with the above procedure with the exception of acetone. This failure is probably due to the formation of the highly volatile and water soluble methyl acetate. The lower limit of sensitivity for the test was determined with methyl isoamyl ketone and was found to be between 2.5 and 5 mg. All saturated aliphatic aldehydes tested gave negative results. Aromatic aldehydes gave positive results because of formation of phenyl formates (14). Positive results were obtained
with a, ,%unsaturated aldehydes because of the formation of trifluoroacetate esters (IO). Mixtures containing both an aromatic or a,,!?-unsaturated aldehyde and a suspected ketone may be identified by extracting a methylene chloride solution of the mixture a t least twice with 10% NaHSOB solution to remove the aldehyde before submitting it to the oxidation procedure. Alcohols and phenols are generally negative to the test procedure with the exception of cyclohexyl alcohols, which are oxidized by the peroxytrifluoroacetic acid to cyclohexanones and consequently give positive results. Carboxylic acids, amides, amines, olefins, hydrocarbons, benzoquinones, sugars, aromatic and aliphatic halides, nitriles, nitro compounds, and ethers are all negative to the test procedure. Oximes, both aldoximes and ketoximes, with the exception of acetone oxime, give positive results. This is a result of the formation of oxime trifluoroacetate (9). The failure of acetone oxime in this test is presumably due to production of water soluble products.
LITERATURE CITED
(1) Baeyer, A., Villiger, V . , Ber. deut. chem. Ges. 32,3625 (1899). (2) Zbid., 33, 124 (1900). (3) Zbid., p. 1569. (4) . , Davidson. D., J . Chem. E d . 17. 81-4 (1940): (5) Davidson, D., Perlman, D., “A Guide to Qualitative Organic Analysis,” Brooklyn College Bookstore, 2nd ed., p. 57, 195s. (6) Doering, W. von, Dorfman, E., J. A m . Chem. SOC.75, 5595-8 (1953). (7) Doering, W. von, Speers, L., Zbid., 72,5515 (1950). ( 8 ) Emmons, W. D., Lucas, G. K, Ibid., 77,2287 (1955). (9) Emmons, W. D., Pagano, A., Zbid., p. 4557. (10) Emmons, W. D., Pagano, A., Freeman, J. P., Ibid., 76,3472 (1954). (11) Friess, S. L., Zbid., 67, 14-15 (1945). (12) Zbid., 71, 2671 (1949). (13) Hawthorne, A I . F., ANAL.CHEM.28, 540 (1956). (14) Wacek, A. v., Bezard, A. v., Be?. deut. chem. Ges. 74B, 845-57 (1941). ,
I
RECEIVEDfor review August 25, 1960. ilccepted October. 24, 1960. Abstracted in part from a thesis for the Master of Arts degree presented by Rubin Drucker to the graduate faculty of Brooklyn College, February 1958.
Microscopic Sublimation Procedure for the Detection and Removal of Impurities from Organic Solids RALPH H. PETRUCCI and JOHN C. WEYGANDT Morley Chemical laboratory, Western Reserve University, Cleveland, Ohio
b Conventional microscopic meking point determinations can b e used to detect impurities in organic solids only if the impurity content is about 1 % or greater. The microscopic sublimation procedure described, by which solids are vaporized and the vapors condensed as liquids, can b e used to detect impurities in organic solids even if the impurity content is on the order of a few hundredths to a few Furthermore the thousandths of 1%. method can b e used for removing trace impurities from organic solids.
0
microscopic procedures that have been described for purity studies ( I , 2) perhaps the most frequently employed is the melting point determination. If a system of two solids, one the major component arid the other an impurity, is of the simple eutectic type, every mixture of the two solids &ill possess two melting points-a “beginning melting point,” corresponding to the eutectic temperature, and an “end melting point,” corresponding to a point on the liquidus curve of the binary phase diagram. F THE SEVERAL
For solids containing small amounts of impurities the only melting point that can be determined with some degree of precision is the end melting point. Since most microscope hot stages permit temperature measurements to within about 1’ C. and since the addition of 1 mole yo of impurity to a pure substance reduces its melting point by approximately 1’ C., the microscopic melting point determination is not effective for detecting trace amounts (less than 1mole %) of impurities. The method of purity determination reported here is an outgrowth of earlier investigations by one of the authors (3, 4). I n these previous investigations it was found that mixtures of organic compounds can sublime a t their eutectic temperatures and that their vapors mill condense to yield a liquid, the eutectic liquid. It is also possible sometimes to obtain a liquid condensate by subliming a solid mixture a t temperatures below the eutectic temperature; in this case the liquid condensate is actually a supercooled liquid solution. I n both cases the general process involves the transitions, solid -+ mixed vapor 4 liquid condensate.
Since the solid components in an eutectic-type system are insoluble in each other, the vapor composition above a mixture of solids is independent of the composition of the solid mixture, being a function simply of the vapor pressures of the pure solids ( 5 ) . Because of this it should be possible t o obtain a liquid condensate, at or below the eutectic temperature, irrespective of the composition of the solid mixture from which this liquid is derived. The parallelism b e h een this statement and the idea that all solid mixtures of the eutectictype should commence t o melt a t the eutectic temperature can readily be seen. But n hereas to observe eutectic fusion the mixtures used must contain perhaps a few mole per cent of the component labeled as impurity, condensation of the vapor above solid mixtures can be observed even if one of the components (the impurity) is present only t o the extent of a few hundredths or a few thousandths of a mole per cent. I t is in dealing Kith substances containing only trace amounts of impurities that this new microscopic sublimation method has its greatest advantage. VOL. 33, NO. 2, FEBRUARY 1961
275
