(8) hIader, P. P., Hamming, W. J., Bellin, A , , AXAL. CHEM. 22, 1181
(1950). (9) May, K. R., Harper, G. J., Brit. J. Ind. M e d . 14,287 (1957). (10) Ranz, K.E., Wong, J. B., Ind. Eng. Chem. 44, 1371 (1952). (11) Schadt, C., Cadle, R. D., ANAL. CHEIII. 29,864 (1957). (12) Schadt, C., Magill, P. L., Cadle,
R.D., Arch. Ind. Hyg. Occupational Xed. 1
, 556 (1950).
(132 “Standard Methods for the Examination of Water, Sewage and Industrial \Tastes,” 10th ed., p. 197, ilmerican Public Health Assoc.. Xew York. 1955. (14) White, H. G., Ind. Eng. C h e k 47, 932 (1955). (15) Whitsell, W. J., J . A i r Pollution Control Assoc. 7, 120 (1957).
(16) Willard, H. H., Furman, N. H., “Elementary Quantitative A4nalysis,” p. 323, Van Kostrand, New York, 1948. (17) Rollcott, E. R., Phys. Rev. 12, 284 (1918). (18) Zavorov, G. IT., Zavodskaya Lab. 23, 541 (1957). RECEIVED for review February 24, 1960. Accepted May 24, 1960.
Interaction of Quinones and Hydrocarbons Investigated by Microscopic Mixed Fusion Analysis DONALD
E. LASKOWSKI
Armour Research Foundation o f Illinois lnsfifute o f Technology, Chicago 7 6, 111.
,Quinones represent potential subclassification reagents for microscopic mixed fusion analysis. To assess their applicability for this purpose, the interactions of nine quinones and 30 hydrocarbons were investigated b y microscopic mixed fusion analysis. Hydrocarbons such as pyrene and 3,4benzpyrene form solid molecular addition compounds with a limited number of quinones; however, the large majority of hydrocarbons studied did not form solid molecular addition compounds. Melting point data and compositions were determined on those systems exhibiting addition compound formation. It is concluded that the quinones may b e used as subclassification reagents in microscopic mixed fusion analysis.
M
mixed fusion analysis involves the preparation of a mixed fusion between an unknown compound and a reagent known to form molecular addition compounds with a given group of organic compounds. Microscopical observation of the mixing zone during solidification and melting places the unknown compound either in the class that forms molecular addition compounds with the reagent used or outside that class. Identification is achieved by microscopical determination of the melting points of the unknown, its molecular addition compound with the reagent, and the eutectics between the molecular addition compound and the two starting components. hfost of the information reported for the identification of aromatic compounds involves the use of 2,4,7trinitrofluorenone as the reagent (8IO). This reagent forms molecular addition compounds with a vaiiety of alkyl, amino, hydroxyl, alkoxyl, and halogen derivatives of benzene (9) ICROSCOPIC
as well as with most polycyclic aromatics (2, 1.2, IS). It would be desirable for more rapid identification or subclassification if additional mixed fusion reagents were available which form molecular addition compounds with more restricted groups of substances 2,4,7-trinitrofluorenone. than does Thus, an unknown could be classified according t o whether it forms an addition compound with 2,4,7-trinitrofluorenone by mixed fusion with this reagent. Subclassification by fusion with a reagent which forms addition compounds with, say, oxygenated aromatics but not with aromatic hydrocarbons, then would provide additional information concerning the structure of the unknown. Similarly, to extend the scope of mixed fusion analysis, reagents are desired for those substances which do not form molecular addition compounds with 2,4,7-trinitrofluorenone. The general task of developing such subclassification reagents has been undertaken in our laboratories. Molecular addition compounds between polynitroaroniatics and polycyclic aromatics or benzene derivatives fall into the general class of donoracceptor addition compounds (1). The polynitro component of the addition compound is considered to function as an electron acceptor while the polycyclic or benzene derivative is considered to function as an plectron donor. Quinones comprise another group of compounds which are considered to be of the acceptor type (1). It can be inferred from the literature that quinones, as a class, represent potentially interesting candidates for subclassification reagents. TTithin this group, a wide variation in addition compound-forming tendencies is noted, Thus, on the one extreme is chloranil which is reported to form solid molecular addition compounds with a variety of
substrates including hydrocarbons, aromatic amines, phenols, and aromatic ethers ( 1 , 14). On the other extreme are the nonhalogenated quinones such as benzoquinone which are reported to form solid addition compounds with hydroquinones, phenols, and aromatic ethers, (1, 14), but little mention is made of solid hydrocarbon complexes with this type of quinone. The interaction of various nonhalogenated quinones with hydrocarbons in solution, as evidenced by color formation, has been reported by various authors (1, 7,11, 14). Thus, it would be inferred that, in so far as formation of solid molecular addition compounds in a mixed fusion is concerned, the quinones would exhibit a substantial degree of selectivity. To evaluate the potential applicability of quinones as subclassification reagents, the addition compound-forming tendencies of nonhalogenated quinones &-ith aromatic hydrocarbons were surveyed. The present communication presents the results of this study. The actual development of quinones as subclassification reagents for microscopic mixed fusion analysis is under investigation and will be reported in a later communication. EQUIPMENT AND REAGENTS
Melting points were measured on a Kofler hot stage purchased from the Arthur H. Thomas Co., Philadelphia, Pa. A microscope fitted with a 17mrn. objective and 1OX eyepiece was used to observe melting. Nixed fusions were prepared on a Kofler hot bar, purchased from the Reichert Co., Vienna, iiustria. The hydrocarbons were purchased from the Aldrich Chemical Co., Milwaukee, Kis., Eastman Kodak Co., Rochester, PI’. Y., or the hfann Research Laboratories, Kew York, N. Y. The quinones were Eastman Kodak, best grade, except for 2-methyl-1,4VOL. 32, NO. 9, AUGUST 1960
1171
naphthoquinone which was purchased from the Aldrich Chemical Co., and vitamin K1 which was purchased from Nutritional Biochemical Corp., Cleveland, Ohio. These compounds were used without purification for the survey studies. When melting points are reported for various binary systems, components were purified by recrystallization, sublimation, or column chromatography. EXPERIMENTAL
The survey to determine the presence or absence of molecular addition compound formation was conducted as follows. Mixed fusions were prepared for each binary combination (30 hydrocarbons with nine quinones). The mixing zone was observed during solidification and the presence or absence of molecular addition compound formation was noted. If no addition compound was observed to form in the mixing zone on complete solidification, the preparation was carefully heated again so that approximately one half of the mixing zone had remelted. The solidification process was then observed microscopically. If the behavior of a given binary system appeared questionable after these observations, the preparation was observed microscopically as the temperature was raised past the melting point of all components. If a particular hydrocarbon was observed to form a molecular addition compound or a colored solid mixing zone, binary mixtures of that hydrocarbon and each of the quinones studied were observed as the temperature was raised past the melting point of all components. If no molecular addition compound was observed to form under these conditions, it was concluded that a stable solid addition compound does not form with the particular binary system under study. The results of these studies are shown in Table I. Of the binary systems reported in Table I, those in which molecular addition compound formation occurred were clear and easy to detect. However, a number of systems exhibited unusual behavior patterns. These include the formation of metastable addition compounds which transform spontaneously to the starting components; the formation of metastable eutectic mixtures which transform thermally to the addition compound; the formation of colored solid mixing zones that melt as if they were eutectics; and the occurrence of chemical reactions between certain quinone-hydrocarbon pairs. &4fter solidification, the acenaphthene-l14-naphthoquinone system had the appearance of a normal eutectic both macroscopically and microscopically. I t also melted as a normal eutectic. However, if the molten mixing zone was allowed to supercool slightly and the solidification process was observed microscopically, a yellow addition compound could be seen to grow rapidly through the mixing zone. 1172
ANALYTICAL CHEMISTRY
Almost immediately as it formed, a transformation to the quinone-hydrocarbon eutectic occurred. In this particular system, therefore, a solid molecular addition compound forms, but it is unstable and decomposes a t a temperature below the eutectic melting point of the original binary composition. This type of behavior has been discussed in detail by Kofler (6). By rapid solidification, both the pyrene-1,4-benzoquinone and the 3 , 4 benzpyrene-1,Cnaphthoquinone systems yielded colorless mixing zones with the microscopical appearance of a normal eutectic. However, on moderate heating of either solidified preparation, transformation to the colored addition compound occurred rapidly throughout the mixing zone. These transformations appeared to be solid phase reactions and once the colored addition compound had formed, the color persisted a t room temperature. The p r e p arations also could be partially melted and the remaining addition compound then grew throughout the mixing zone. Although this behavior could be interpreted to indicate that an energy of activation is required for the formation of these two particular molecular addition compounds, it is more probable that the rates of nucleation and growth of these particular addition compounds are slow compared to the corresponding rates of the starting components. Hence, the starting components grow through the mixing zone and crystallize as a metastable eutectic before a substantial amount of addition compound has the opportunity to form. Because some addition compound nuclei must have formed during the solidification process, moderate heating speeds up the rate of growth of the addition compound so that the mixing zone achieves the most stable state-the addition compound. This transformation (metastable eutectic to addition compound) was also obseryed to occur very slowly a t room temperature. When the 2,3-benzfluorene-2,5-diphenyl-1,4-benzoquinone system was heated for any appreciable time above the melting point of the components, a blue-black solid material was seen to form. This material was not a normal addition compound because when reasonable care was exercised not to overheat or to prolong the heating, the system was seen to have a normal eutectic behavior. In all probability, the blue color resulted from chemical changes greater in extent than mere formation of an addition compound. Although the 2,5-dimethy1-ll2-benzanthracene-l14-benzoquinone system appeared to be a simple eutectic, a colorless solid phase was seen to exist in the mixing zone a t temperatures above the melting point of either component. This material did not have the
usual appearance of an addition compound, but rather it appeared to form as the result of a thermal reaction between the quinone and hydrocarbon. iln equimolar mixture of quinone and hydrocarbon was placed on the hot stage a t 130' C. and allowed to stand. Initially, complete melting to a redorange liquid occurred. After standing several minutes a t this temperature, colorless crystals could be seen to form and grow slowly in the melt. From this behavior, it can be concluded that the third solid phase in the 9.10-dimethyl1,2 - benzanthracene - 1,4 benzoquinone system is actually the product of a chemical reaction and not an addition compound in the sense meant here. A number of the systems in Table I yielded colored mixing zones after solidifleation, although it is indicated in Table I that addition compound formation does not occur. On heating, only one melting point was observed in the mixing zone, indicating a eutectic. With the 9,10-dimethyl-1,2-benzanthracene-2-methylanthraquinone system, the color was observed to disappear on moderate heating and appeared to be due t o the presence of a colored supercooled melt in the mixing zone. All systems with this hydrocarbon were noted to supercool markedly. The following binary systems had colored solid mixing zones, the color persisted to the melting point, and the melting appeared uniform throughout the mixing zone: pyrene-9,lO-anthraquinone; 3,4benzpyrene-2-methyl-9, 1C-anthraquinones; 4-methylpyrene-2methyl - 9,lO - anthraquinone; 9 methylanthracene - 9,lO - anthraquinone; and 9-methylanthracene-3methyl - 9.10 -anthraquinone. Preparations with 2 - methyl - 9,lO - anthraquinone and 3,4-benzpyrene or 4methylpyrene were allowed to stand for several hours a t 80' to 100' C. without apparent alteration of the color of the solid mixing zone. Because these colored solids persist to the melting point and because they form by either slow or rapid cooling of the melt, it is reasonable to assume that they represent a stable rather than a transient stage. It is tentatively assumed that these result from partial mutual solid solubility, although this could only be confirmed by more detailed phase diagram studies than those reported here. The yellow-orange solid phase present in the 4-methylpyrene-2-methyl1,4-naphthoquinone system exhibited a different type of behavior. With this system the color disappeared on heating and eutectic melting was noted. If the preparation were allowed to cool slowly so that the mixing zone supercooled, a definite addition compound could be seen to crystallize spontaneously a t 71-2' C., approximately 8" below the observed eutectic temperature
-
Table 1.
Hydrocarbon
Qualitative Observations on Quinone Hydrocarbon Mixed Fusions
l,.l-Benzoquinone
Quinone ~2,5-Di- 2,5-Di2-Methyl%Methyl2-Methyl- methyl- phenylL49,lO1,4benzo- 1,4benzo- l,+benzo- 1,4Naphtho- naphtho- 9,lO:Anthra- anthra- Vitamin quinone quinone quinone qumone quinone quinone quinone KI
nurene Hexamethylbenzene trans-Stilbene
-
-
Ye1
-
-
+
Ye1 org Ye1 grn -
Light ye1
-
-
+
-
-
-
Ye1 grn
+
-
-
-
-
-
Ye1 grn
Ye1 org Light ye1 org
Biphenyl Naphthalene 3-Methylnaphthalene Acenaphththene Anthracene 9-lllethyhthracene
-
-
-
-
-
Ye1
Ye1
Ye1 grna
Ye1
Pale ye1 grn Ye1
Ye1 org
Ye1 org Ye1 gm
Ye1 org Pale ye1
Org
Ye1 org Ye1 gmb
Ye1 Deep ye1 Ye1 orgb
-
-
-
-
Ye1 org Org
+
Org
-
-
-
-
-
-
-
Red org Org
Phenmthrene 2-Methylphenanthrene 3-Methylphenanthrene Fluorene
Fluoran thene
-
3,4Benzfluoranthene
-
ll,l>Benzfluoranthene Chr ysene 1,%Benzanthracene 9, l0-Dimethyl-lI2-bena-
anthracene
20-Methylcholanthrene 1,2,5,6Dibenzanthracene Pyrene 1-Methylpyrene PMethylpyrene l,>Benzpyrene 3,PBenzpyrene Perylene 1,12-Benzperylene Saphthacene
Pale ye1 grn -
Ye1
Ye1 grn
-
-
-
-
-
Ye1
Org
Ye1
Ye1
Ye1
-
-
-
Ye1 org Ye1 org Ye1 org
-
-
Red org Ye1 org
-
-
-
-
Org
Org
Org
Red org Org
-
-
Ye1
Red org Ye1
-
-
Org
Org
Org
Org
+ -
+
-
-
Ye1 org Org
-
-
-
-
Ye1
-
Ye1 org
Ye1
Ye1 Ye1 grnb
-
-
Org
Ye1 org Ye1
Ye1
Ye1
Ye1 org
Org Ye1 org Ye1 org* Yelb
Ye1 Ye1 Ye1 grn*
-
-
+ -
-
Ye1 grn Ye1
-
-
-
-
-
-
Ye1
Ye1 org
-
+
Org
Pale org Ye1
Org
Pale ye1 grn
Red
Org
Org
Org
Ye1 org
-
-
-
-
-
Ye1 org Ye1 org Org*
Org
Red org Ye1 Org
-
Red org Org
+
-
-
Org
Red org Red org
-
-
-
-
-
-
+
-
-
-
Org -
Ye1 org Not tested
-
-
-
-
Org
Ye1 org
-
Ye1 org -
-
Ye1 0% Minus sign ( - ) indicates that no stable solid molecular addition compound formed; color given is color of mixing zone when melted. Plus sign (+)indicates that stable solid molecular addition compound formed; color given is color of solid molecular addition compound. a See text. * Color of solidified mixing zone.
VOL. 32, NO. 9, AUGUST 1960
1173
for this system. When the colored solid mixing zone was observed after standing approximately 24 hours at room temperature, small transformation zones could be observed scattered throughout the mixing zone. On heating, these areas gradually spread throughout the mixing zone and only the eutectic melting a t 78.5" to 80" C. was observed. This particular system, then, is similar to the acenaphthene1,4naphthoquinone system, although the metastable addition compound is far more stable than is the metastable acenaphthene addition compound. Melting points of the molecular addition compounds and the eutectic temperatures were determined for the various systems in which addition compound formation occurred. The 9methylanthracene addition compounds were not measured because this particular compound had a 6" C. melting point range even after two chromatographic separations on silica gel. The various melting points are shown in Table 11. These melting points were determined at a heating rate of 3" C. per minute and the hot stage thermometer was calibrated with known melting point standards.
Table II.
Each melting range cited represents the minimum and maximum temperatures from a t least three separate observations. The eutectic temperatures reported are those a t which pronounced eutectic melting occurred. For many of the systems, slight melting at lower temperatures, due to small amounts of impurities, was noted. These temperatures are not included in Table 11. The incongruent melting points reported in Table I1 were especially difficult to determine. This was due to the fact that the molecular addition compound rapidly dissolved in the molten eutectic, leaving only a thin line of addition compound adjacent t o the second compound (usually the hydrocarbon). The final temperature a t which the addition compound decomposed was, therefore, difficult to determine. However, the values reported in Table I1 for incongruent melting points are believed to be accurate, because they are the result of a number of independent determinations. Melting point data were determined on binary mixtures of each hydrocarbon and quinone shown in Table 11, although only data on systems in which stable solid addition compounds formed
Mixed Fusion Data for Quinone-Hydrocarbon Systems
Melting Range, C: EutecticEutecticaddition addition compoundcompoundhydroilddition carbon compound quinone 104.1-05.3 120.1-21.2 123.6-24.9 -
Components Quinone Hydrocarbon 1,CBenzoquinone (m.p. Pyrene (m.p. 115-15.5' C.) 149.5-50 9" C.) 2-Methyl-lI4-benzoPyrene quinone (m.p. 67.17.6' C.) 1-Methylpyrene 2-M~thyl-l14-benzo(m.p. 146-48.7' quinone
63.5-4.8 53-53 8
O
108 2-09 b
109.5-10.4 64.2-4.7'
C.)
2,5-Dimethyl-1,4-benzo- Phenanthrene (m.p. 99.5-100° b 76.5-7.7 84.9-5' quinone (m.p. 124.5rl? 24.9" C.) u. J 2,5-Dimethvl-1,4-benzo- Pyrene 119.8-21.2 138.3-38.7 157.5-58.3 quinone 2,5-Dimethyl-l, 4-benzo- 4-hfethylpj~ene 110.8-11 8 117.7-18 7 120.5-21.6 (m.p. 143.5quinone 44.7' C.) 2,5-Dimethyl-l,Cbenzo- 3,PBenzpgrene 117-18 136.5-38 139-41 quinone (m.p. 175.6-77' 1,4-Kaphthoquinone
c.1
Hexamethylben10242.7 108 5 zene (m.p. 165.8-66.8" C.) 1,4-Naphthoquinone 101.843.1 b 3,4-Benzpyrene 6 2-Methyl-l,4-naphthoHexamethylben86-7,2 quinone (rn.p. 106.1zene (m.p. 124 1-25' C.)
07.1' C.)
2-Me,thyl-1,4-naphthoquinone
2-hfethyl-1,4-naphtho-
106. 1-07c
10344.8"
Pyrene
79.6-80,l
b
82.5-2.9'
3,4-Benzp>~ene
90.8-2 5
b
106.6-06 8 O
Hesamethylbenzene
137.9-38 2
133,T-34.2
Melting points determined a t heating rate of 3' C./min. Eutectic absent because addition compound melts incongruently. Incongruent melting point. 1174
109.1-09.5
ANALYTICAL CHEMISTRY
139 8-40
are reported. Those pairs not reported appeared to be eutectic systems, although the systems with l-methglpyrene and 4-methylpyrene have rather broad eutectic melting point ranges. It is possible that unstable solid addition compounds are present with these particular systems but were not detected by the methods of examination employed here. Because most of the solid addition compounds reported in Tables I and I1 are not believed to be previously reported in the literature] it was decided to determine their composition. Known mixtures were weighed into vials and intimately ground. A large amount of mixture was placed on a microscope slide and covered with a cover glass. The mixture was then rapidly fused and rapidly cooled. The preparation was then placed in the hot stage a t a temperature 5" to 10" below the expected final melting point with the heating rate adjusted to 4" to 5" per minute. The melting point was determined on the material in the center of the preparation and the value so determined was compared with the melting point measured on a contact preparation of the same components under identical heating conditions These precautions were necessary because of the high volatility of the components, especially 1,4benzoquinone The results of these measurements are shown in Table 111, with the composition of the addition compounds deduced from the melting point data. Although in some cases the melting points of the mixtures deviate more than would be desired from the melting point of the corresponding addition compounds as determined on contact preparations, the ratios of quinone to hydrocarbon in the addition compound as quoted in Table I11 are reasonable deductions from the data. DISCUSSION
The expected selectivity of the nonhalogenated quinones has been amply demonstrated by this study. Three of the quinones-2,5-diphenyl-l,4-benzoquinone, 9,10-anthraquinonej and vitamin K,-did not form solid addition compounds with any of the 30 hydrocarbons tested. The other quinones studied formed solid addition compounds with a limited number of the polycylic aromatics. The formation of a solid addition compound does not appear to be limitcd to any particular polycyclic system, although the pgrene series appears to be favored. Kithin the pyrene series, small changes in structure appear to cause major differences in behavior. For instance, pyrene forms solid addition compounds with 1,4-benzoquinone, 2-methyl- and 2,5-dimethyl-l,4-benzoquinone,and 2-
methy1-lJ4-naphthoquinone.13Iethylpyrene forms a solid addition compound only with 2-methyl-lJ4-benzoquinone while 4-methylpyrene forms a stable solid addition compound only with 2,5dimethyl-lJ4-benzoquinone. Because a subclassification reagent was desired, it would appear that 2,5diphenyl-1,4-benzoquinone offers the most potential. This compound does not form solid addition compounds with any of the hydrocarbons studied. Preliminary mixed fusion studies indicate that it forms molecular addition compounds with hydroquinones, phenols, and aromatic ethers, so it should be useful to subclassify unknown compounds which have been placed in the donor class by addition compound formation with 2,4.7-trinitrofluorenone. The actual utility of this reagent, however, has not yet been determined. The present studies have served to indicate the presence or absence of stable solid addition compound formation and the melting points and composition of the addition compounds for those systems in which addition compound formation occurs. Such limited information cannot be expected to explain 1%-hysolid addition compounds form between certain hydrocarbons and quinones but not between others very similar in structure. No correlation appears to exist between either the standard oxidation reduction potentials of the quinones as tabulated by Fieser and Fieser (3) or the ionization potentials of the hydrocarbon as calculated by Hedges and Matsen (4). The explanation must be closely related to subtle factors influencing the energetics of crystal formation. A possible clue in this direction exists in the rather widespread formation of colored mixing zones observed in this
work. This behavior has been noted with many other acceptor-donor pairs (1, 9, 14) and it has been taken to indicate that, in the liquid phase, a molecular addition compound does form between the donor and the acceptor. However, on crystallization the two components crystallize separately rather than as the addition compound. Thus, not only must the energetics of addition compound formation be taken into account but also the heats of fusion of the components of the addition compounds must be considered. In a t least two instances in the present study, the actual crystallization of the unstable addition compound was observed, lending support to the supposition that the formation of color in the melt indicates the formation of an addition compound. It mould be expected that, if the various colored melts could be supercooled far more than was done in the present study, many more such unstable addition compounds would be observed. The colors observed with 2,5-diphenyl1,4-benzoquinoneJ on the other hand, are believed to be due as much to the actual color of the quinone in solution as to the formation of addition compounds in the melt. Of the quinones studied, 2,5-dimethyl1,4-benzoquinone appears to be the most prone to form solid molecular addition compounds with hydrocarbons. Thus, this compound forms solid addition compounds with phenanthrene, 9-methylanthracene, pyrene, 4-methylpyrene, and 3,4-benzpyrene. Considering only electronic effects, the substitution of methyl groups for hydrogen in the quinone lvould be expected to make the quinone less effective as an acceptor. The methyl group substituted adjacent to the quinone oxygen of lJ4-naphthoquinone and 9,lO-
Table 111.
Addition Compound Compositions
Components of Mixture Quinone Hydrocarbon 1,4-Benzoquinone Pyrene 2-Methyl-1,4-benzoquinone Pyrene 2-hlethyl-l,4benzoquinone 1-Methylpyrene 2,5-Dimethyl-1,4-benzoquinone 2,5-Dimethyl-1,Pbenzoquinone 2,5-~imethyl-1,4-benzoquinone 2,5-Dimethyl-1,4-benzoquinone
Pyrene 4-Methylpyrene 3,4-Benzopyrene Phenanthrene
1,Ph'aphthoquinone 1,4-Naphthoquinone
Hexamethylbenzene 3,4-Benzpyrene
2-Methyi-l,4naphthoquinone 2-Methyl-1,Cnaphthoquinone 2-Methyl-1,Cnaphthoyuinone 2-Methyl-9,lO-anthraquinone
anthraquinone also seems to promote the formation of solid addition compounds. This could be due to factors affecting heats of fusion as mentioned previously or it could indicate a special effect of alkyl substitution on the quinone ring. I n solution studies, alkyl substitution of the quinone ring has been reported to decrease the equilibrium constant for addition compound formation betn-een oxygenated aromatics and quinones ( 5 ) . The 2 - methyl - 9,lO - anthraquinone mixed fusions with 4-methylpyrene and 3,4-benzpyrene were particularly confusing. The colored solid phases noted have been tentatively concluded to be due to solid solution formation. However, it is by no means certain that this is in the case and it will be necessary to confirm these tentative conclusions by detailed phase diagram studies. The molecular addition compounds found to melt congruently also had a 1-1 mole ratio of quinone to hydrocarbon. Except for the phenanthrene2,5-dimethyl-lJ4-benzoquinone addition compound, the incongruently melting addition compounds had a 2 : l quinone to hydrocarbon mole ratio. Vitamin K1 was included in this study because it is a biologically active quinone and several of the hydrocarbons studied are potent carcinogens. Because 2-methyl-1.4-naphthoquinone also possesses vitamin K activity, and because this quinone was noted to form a solid molecular addition compound with 3,4-benzpyreneJ vitamin Kl was also investigated. Vitamin K1 is an oily liquid, whereas the other quinones studied are solids. No solid addition compounds were observed to form with this quinone, although colored mixing zones were formed in mixed fusions between it and acenaphthene, 1,Zben-
Mole % Quinone in Mixture 50.2 50.1 50.3 66.9 50.2 50.1 50.2 49.9 63.5 50.7
Final Melting Point f; Mixture, C. 125 111
80
Melting Point Ratio of of Addition Quinone to Compound in Hydrocarbon in Contact Addition Preparation Compound 124.6
110
64.2
61 ._
141
140 85
120
109-109.5
108.9
1:l
160 121.5 86 101
110 106.2
158
Hexamethylbenzene
115
102.9
Pyrene
48.3
90
81.5
3,4Benzpyrene Hexamethylbenzene
64.8 50.2 67.0 49.5
...
2: 1 1:l 1:l 1:l 1:l
49.2 66.1 49.5
66.8
1:l 1:1
ioi.5 80
115
104 140.3
105.8
106 139.9
VOL., 32, NO. 9 AUGUST 1960
.
I
.
2: 1
...
2 :1
...
2: 1
...
2 :1 1:l
1175
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 the sample, using heat if necessary. Some high molecular weight glyoxals do not dissolve readily in this aqueous mixture, so, in general, it 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
