zanthracene, pyrene, 3,4benzpyrene, 1,Zbenzpyrene, 1-methylpyrene, 4niethylpyrene, 9-methylanthracene, 20methylcholanthrene, 9,10-dimethyl-1,2benzanthracene, perylene, and naphthacene. It is possible that further study of interactions of this type may offer a clue to the biological activity of some of these hydrocarbons. I n summary, it may be stated that the formation of solid addition compounds between quinone and hydrocarbons is a highly sensitive function of the structure of both components. It should be possible to select one or more effective microscopic mixed fusion subclassification reagents from the group of quinones studied. At the present time, 2,5-diphenyl-l,4benzoquinone appears to offer the most promise. This quinone did not form solid molecular
addition compounds with any of the hydrocarbons studied. It is expected that it will form addition compounds with oxygenated aromatics and, hence, that it may be used to subdivide further the broad category of substances known t o form addition compounds with 2,4,7-trinitrotluorenone. LITERATURE CITED
(1) Andrews, L. J., Chem. Revs. 54, 713 (1954). (2) Dajac Laboratories, Leominster, Mass., Dyta Sheet, “2,4,7-Trinitrofluorenone, 1954. (3) Fieser, L. F., Fieser, M., “Organic Chemistry,” pp. 754-5, Heath, Boston, Mass., 1950. (4) Hedges, R. M., Matsen, F. A,, J. Chem. Phys. 28,950 (1958). ( 5 ) Hunter, W. H., Xorthey, E. H., J. Phys. Chem. 37,875 (1933).
(6) Kofler, L., Kofler, A., “Mikromethoden zur Kennzeichnung organischer Stoffe und Stoffegemische,” Innsbruck Univ., Kagner, 1948, unpublished translation by W. C. McCrone, Jr. (7) Kuboyama, A., Nagakura, S., J. Am. Chem. SOC.77, 2644 (1955). (8) Laskowski, D. E., Grabar, D. G., McCrone, W. C., AXAL. CHEM. 25, 1400 (1953). (9) Laskowski, D. E., McCrone, W. C., Ibid., 26, 1497 (1954). (10) Ibid., 30, 542 (1958). (11) hiichaelis, L., Granick, S., J. Am. Chern. SOC.66, 1023 (1944). (12) Orchin, hi^, Reggel, L., Woolfolk, E. O., Ibid., 69, 1225 (1947). (13) Orchin, M., M7001folk, E. O., Ibid., 68,1727 (1946). (14) PfeilTer, P., “Organische Molekulverbindungen,” 2nd ed., pp. 274-300, Ferdinand Enke, Stuttgart, 1927.
RECEIVED for review February 24, 1960. Accepted May 23, 1960.
Determination of GIyoxaIs and Their Sodium BisuIfite Add; tion Products by Potentiometric Titration JOSEPH G. BALDINUS and IRVIN ROTHBERG Smith Kline & French laboratories, Philadelphia 7, f a .
,Aromatic glyoxals may b e assayed by the Cannizzaro reaction. The glyoxals are quantitatively converted to the corresponding mandelic acids, and the alkali consumed is titrated potentiometrically with acid. Because sodium bisulfite reacts with sodium hydroxide to form sodium sulfite, the method may be extended to the bisulfite addition products. With the addition products, the potentiometric breaks obtained are very small; however, these can b e greatly magnified by oxidizing the sulfite to sulfate with hydrogen peroxide just before the end point is reached.
D
pharmacological studies on aromatic glyoxals and their sodium bisulfite addition products, a method was needed to determine the purities of these compounds. Various colorimetric ( 1 , 16), gravimetric (2, 67, and ion exchange (6) methods have been reported, but these procedures either require a standard for comparison or are too time-consuming. In a volumetric method devised by Friedemann (3) the glyoxal is converted into two carboxylic salt functions with alkaline hydrogen peroxide; the excess alkali is then titrated with standard acid. Originally, Friedemann applied this method only to aliphatic glyoxals; URIXG
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ANALYTICAL CHEMISTRY
more recently, other investigators (11) have used it to assay both aromatic glyoxals and their sodium bisulfite addition products, with excellent results. This method, however, cannot be used in the presence of other oxidizable impurities. This paper describes a titrimetric method based on the Cannizzaro reaction. Salomaa (IS) and Hofreiter, Alexander, and W O E (8) have published procedures similarly based on this reaction. Their procedures, however, were designed specifically for glyoxal and dialdehydes of oxidized starches, respectively, and thus cannot be used for water-insoluble glyoxals. Also, it will be demonstrated that it is not practicable t o apply these procedures, as such, t o the sodium bisulfite addition products. The proposed method has no such limitations; and may be used to assay both aromatic glyoxals and their sodium bisulfite addition products. As a further check on the purity of the sodium bisulfite addition products, the sodium was titrated in nonaqueous medium with perchloric acid. SPECIAL REAGENTS
Standard aqueous hydrochloric acid,
0.2N,standardized by taking National Bureau of
Standards benzoic
acid
through the procedure described for aromatic glyoxals. Perchloric acid, 0.1N, in glacial acetic acid (4). APPARATUS
Either a Photovolt Model 110 or a Beckman Model G p H meter equipped with glass and calomel electrodes. PROCEDURES
General Procedure. Weigh 1.5 to 2.0 meq. of glyoxal or bisulfite addition product into a 250-ml. alkaliresistant flask. Add 50 ml. of methanol, follow with 25 ml. of water, and dissolve t h e sample, using heat if necessary. Some high molecular weight glyoxals do not dissolve readily in this aqueous mixture, so, in general, i t may be desirable t o dissolve the glyoxals in methanol before adding water. Next, pipet 10 ml. of 0.5.V sodium hydroxide into the flask, draining the pipet for a definite time. Connect the flask to an air condenser, and reflux gently on a steam bath for 1.5 hours. The solution turns yellow, which is normal. Remove the flask from the condenser, insert a glass stopper, and cool t o room temperature. Transfer Ohe contents with water to a 400-ml. beaker and lower the electrodes into the solution. Conduct a blank determination with the sample, wing the same pipet for measuring the sodium hydroxide solution, and draining
DISCUSSION the same length of time. For the actual titration, use Method A or B, depending Table I. Determination of Purity of The method for aromatic glyoxals on the nature of the sample. Aromatic Glyoxals by Cannizzaro A. AROMATICGLYOXALS. Turn on is based on the Cannizzaro reaction: Reaction the stirrer, and titrate with 0.2N hydroNaOH ArCHOHCOONa ArCOCHO chloric acid. Add the acid rapidly in Purity, Lit. the beginning, but near the end point, Compound Wt. Ref.b After the reaction has gone t o comslowly, and in increments of 0.1 ml. p-Chlorophenylglyoxal. Record the potential reading after each pletion, the excess alkali is titrated 99.9",' '/z Hz0 addition of titrant, and use the second potentiometrically with acid. The end p-Bromophenylglyoxal. derivative method (IO) to calculate the 99.3 point is easily determined because the '/2 H2O end point. The difference in acid rea-Naphthaleneglyoxal. change in potential at the equivalence quired for the blank and the sample is a 101,7 1 H,O point is large and abrupt. measure of the amount of glyoxal p-Methoxyphen ylglyoxal. I n only one instance has the method 98.8 1 H?O present. m-hlethoxyphenylglyB. BISULFITE ADDITIONPRODUCTS. given trouble. This was a high molecoxal.'/2 H20 99.2 (11) ular weight glyoxal which did not Add 5 drops of 1% phenolphthalein solution, start the magnetic stirrer, dissolve completely in aqueous metha Av. of two determinations. and titrate with 0.2N hydrochloric acid anol, and was carried through the * Method of preparation and structure until the indicator becomes colorless. procedure anyway. During refluxing of hydrate. Add 1 ml. inore of titrant so t h a t there a reddish oil formed, and the solution Std. dev. calculated from 4 determinais a n excess of hydrochloric acid. Add tions =!=0.487c. became turbid. Not surprisingly, the 5 ml. of 3% hydrogen peroxide solution, assay value was low. When the glyoxal and back-titrate the acid with 0.1N was dissolved in methanol, as directed sodium hydroxide. Add the alkali in the analytical procedure, the rein 0.1-ml. increments, and calculate the end point as described in Method -4. fluxing solution remained clear, and to coerce the end point were unsuccessCalculate the purity as follows: results were quantitative. T h e exact ful. nature of this turbid by-product is not T o get a satisfactory end point, known; it may be related to the dimer Topurity it was necessary to remove the sodium of phenylglyoxal reported by Sodersulfite. For this purpose hydrogen baum (14). where N , is the normality of acid, peroxide was added; this oxidized The sodium bisulfite addition prodA r b the normality of base, A the ml. of the sulfite t o sodium sulfate which acid added to the blank, B the ml. of ucts also undergo the Cannizzaro reacis a neutral salt. The point a t which base t o back-titrate the acid in the tion, which proceeds concurrently with the hydrogen peroxide is added was blank, C the ml. of acid added t o sample, the reaction: found t o be critical. If the peroxide D the ml. of base t o back-titrate the was added when the reaction mixture acid in sample, E the gram equivalent NaHS03 S a O H + KazSOa f HzO was alkaline, the results mere erratic weight, and W the grams of sample and often high. However, if the taken. Because this niix+ure contains salt DETERMINATION OF SODIUM. Weigh peroxede was added during the titraof two acids, which have different out approximately 1 meq. of bisulfite tion, after the phenolphthalein had dissociation constants, the changes in addition products. Add 200 ml. of turned colorless, the results obtained potential occurring during the titration glacial acetic acid, and heat t o effect so small that i t was difficult to were were quantitative. complete solution. Titrate potentioBecause the reaction mixtures are judge the location of the end point. metrically with O.1N perchloric acid alkaline, the usual precautions should To overcome this ambiguity, various and calculate the end point by the techniques were tried: The reaction be observed to minimize exposure to procedure described in Method ,4. atmosphere. The slight absorption of mixture was saturated with sodium chloride before titration (9) in the hope carbon dioxide that does occur will RESULTS be taken care of by the blank, which is that this would sharpen the end point. treated in exactly the same way as Another approach was t o time the Table I summarizes the results obthe sample. I n the titration, carbonate reactions-Le., the potential was read tained with five aromatic glyomls. gives rise to a small inflection that apat a specified time after adding each The structures for these glyoxals have pears just beforc. the end point correincrement of acid. All such efforts been reported in the literature; actually, they are hydrates and contain 1 or 0.5 mole of water depending on the glyoxal. In every case, the purity reported in Table I is in accord with the Table II. Percentage Purity of Bisulfite Addition Products Determined b y Cannizestablished hydrate structure. zaro Reaction and Titration of Sodium Purity data for various sodium biPurity, Weight yo5 sulfite addition products are assembled Cannizzaro Sodium in Table 11. These purities were Lit. Ref. Compound reaction titration determined by the Cannizzaro reaction, p-Chlorophenylglyoxa1.NaHSOa 99.0 100.5 (11) and, also, by titrating the sodium in p-Bromophenylglyoxa1,NaHSOa 100.0 99.5 (11) nonaqueous medium. The latter purity m-Methoxyphenylglyoxal.NaHS0," 100.0 98.6 (11) determination is particularly useful if p-Methoxyphenylglyoxal.KaHSOae 98.8 99.7 (11) some of the bisulfite has been oxidized p-Methylphenylglyoxa1.NaHS08~d 99.7 100.0 ... by air. Sodium bisulfate consumes a Av. of two determinations. alkali and interferes in the Cannizzaro b Previous workers have reported these compounds a8 hydrates. The compounds in reaction; this compound, however, this table were dried in vacuum a t 60" C. for 4 hours, which accounts for their being does not titrate in glacial acetic acid anhydrous. (18). The compounds in Table I1 e Compound not reported previously. Elemental analysis gave: C, 42.74; H, 3.91. were dried in the vacuum oven before Calcd. for compound: C, 42.86; H, 3.60. d Std. dev. calculated from 5 determinations =!=0.6170. analysis, and the purities are calculated on the anhydrous basis.
+
-
+
VOL. 32, NO. 9, AUGUST 1960
1177
sponding t o the neutralization of the alkali. This inflection is very small, and is not likely to be confused with the true end point that follows. A refluxing time of 1.5 hours has proved generally satisfactory for both the glyoxals and their bisulfite addition products. For individual compounds, it is possible that a shorter reaction time will suffice. LITERATURE CITED
(1)Ariyama, N.,J . Biol. Chem. 77, 359 (1928).
(2) Becke, F., Gross, O., Z. anal. Chem. 147,9 (1955). (3)Friedemann. T. E.. J . Biol. Chem. 73,331(ig27j. (4)Fritz, J. S., “Acid-Base Titrations in Nonaqueous Solvents,” p. 13, G.
J. J., LLElectrochemical Chemistry,” 2nd ed., p. 93,Interscience, Xem- York, 1958. (11) Moffet, R. B., Tiffany, B. D., Aspergren, B. D., Heinzelman, R. V., J . Am. Chem. Soc. 79,1687(1957). (12)Pifer, C. W.,Wollish, E. G., ANAL. CHEM.24,519 (1952). (13) Salomaa, P.,Acta Chem. Scand. 10, (10)Lingane,
Frederick Smith Chemical Co., Columbus, Ohio, 1952. ( 5 ) Gabrielson, G., Samuelson, O., Svensk
Kern. Tidskr. 62, 214 (1950). (6) Glasstone, S., Hickling, A., J . Chem. SOC.1936. 824. (7) Goldyrev, L. N., Postovskii, I. Y., J. Gen. Chem. U.S.S.R. 10,39 (1940). (8)Hofreiter, B. T., Alexander, B. H., Wolff, I. A., ANAL. CHEM. 37. 1930 (1955j. (9) Xolthoff, I. M., Z. anorg. u. allgem. Chem. 109,69 (1919).
306 (1956). (14)Soderbaum, H. G.,Ber. 24, 1386 (1891). (15) Wise, C. S., Rlehltretter, C. L., Van Cleve, J. K., A x . 4 ~ . CHEW 31, 1241 (1959).
RECEIVED for review February 29, 1960. Accepted May 20, 1960.
Surface-Active AI kylene Oxide Condensation Products Determination of Polyethylene Glycols in Selected Cationic Ethylene Oxide Condensates J. V. KILHEFFER, Jr., and ERIC JUNGERMANN Armour lndustriul Chemical Co., 7 355 West 3 Jst St., Chicago 9, 111. ,A method has been developed for the determination of free polyglycols in a group of cation-active ethylene oxide condensates. The polyglycols are isolated as dilute aqueous solutions by batch treatment with ion exchange resins. Both the amount and the average molecular weight of the polyglycols are then obtained from the results of two rapid and simple determinations: a spectrophotometric analysis and a dichromate total oxidation.
of the present-day commercial surface-active agents have, as the hydrophilic part of their structures, one or more polyoxyethylene chains. These products are usually prepared by the base-catalyzed addition of ethylene oxide to a hydrophobic substrate containing one or more replaceable hydrogen atoms (14). The surfactants are not single chemical species, because the starting hydrophobe is often a mixture and the ethylene oxide addition invariably gives a range of chain lengths, distributed about a most frequent value. Flory (7) predicted that the distribution should be Poissonian, and several investigators have reported data (2, 6, 10, 11, 16) which show a t least qualitative agreement with Flory’s theory. Two classes of surfactants may be prepared by this process. Thus, nonANY
1178
ANALYTICAL CHEMISTRY
ionic materials are obtained from carboxylic acids (usually fat- or rosinbased), alcohols, phenols, polypropylene glycols, mercaptans, and amides; primary or secondary amines, on the other hand, yield cation-active products, which may, in turn, be quaternized to even more strongly cationic derivatives. During t,he addition of ethylene oxide, the presence of water leads to the formation of polyethylene glycols. The low molecular weight of water and its reactivity toward ethylene oxide imply that the percentages of these glycols may become large, especially in the products containing many moles of ethylene oxide. The similarity of the structure of the glycols to that of the desired adducts makes their removal usually impractical, so that commercial surfactants of this kind are mixtures. Because the presence of glycols in the products may affect their performance in some applications, i t is important to know the extent of their formation. CHEMISTRY AND STRUCTURE
I n the addition of ethylene oxide to a primary amine, for example, the amino hydrogens are rapidly substituted, but in the absence of a catalyst, further condensation (ITith the hydroxy groups of the 2-mole adduct) is negligible (12). The production of higher condensates is catalyzed by strong alkalies, which
convert the hydroxy groups to the reactive conjugate anions (4, 20) the complexity of the product mixture increases rapidly with the oxide-amine ratio as the result of the presence of two reactive sites, not only in the original substrate, but in each successive adduct. The origin of the numerous constituents can Le seen in the schenie of Figure 1, in which the expression nz, n represents the substance H(OCH2CH2),KR(CH2CH20),,H, and the specific rate constant. k,,, corresponds to the reaction in which the eompound(m, n) is converted to the compound ( m f l , n). Lack of quantitative values of the rate constants precludes predictions of the exact distribution of the product mixture, although some qualitative inferences may be drawn from results appearing in the Literature. The order of reactivity appears to be 0 - > XH > OH, because amines add ethylene oxide in the absence of alkali, but the bis(hydroxyethy1)amines (12) or alcohols (4,80) do not, and because large amounts of caustic catalyze the formation of a product containing a considerable amount of primary and secondary amines, even after the addition of several moles of ethylene oside (12). With smaller amounts of alkali, the product is chiefly tertiary aminesi.e., both amino hydrogens react before appreciable chain lengthening
