A Thermochromic Test for Polycyclic p-Quinones EUGENE SAWICKI, THOMAS W. STANLEY, and THOMAS R. HAUSER Community Air Pollution Program, Robert A. Toft Sanitary Engineering Center, Public Health Service, U. S. Department of Health, Education, and Welfare, Cincinnati 26, Ohio Many
compounds
containing
the
0
0 versible thermochromic reaction in reducing media. This test i s useful for unsubstituted polycyclic p-quinones, such as 9,10-anthraquinone, 5,12naphthacenedione, 6,13-pentacenedione, 7,12-benzo [a]anthracenedione, and naphtho [2,3-a]pyrene-7,12-dione -e.g., boiling a pink dimethylformamide solution of 5,12-naphthacenedione in the presence of potassium borohydride gave a dark blue sohtion, which upon cooling became pink again, This color change can be repeated at least a dozen times. The color reaction has been applied to air particulate matter in that the presence of polycyclic quinone-like compounds has been demonstrated in the aromatic fraction.
A
s
a portion of a routine air analysis operation in this laboratory, total and benzene-qoluble air particulate loadings are determined for a number of cities in the Pnited States. The benzene extracts are fractionated, on the basis of solubilitv, into watersoluble, acidic, basic, and neutral fractions. The neutral fraction is further separated chromatographically into aliphatic, aromatic, and oxygenated subfractions ( 5 ) . Of the total aromatic content of the crude benzene extract, as measured by the piperonal chloride test (S), approxiniately 80% appears in the neutral aromatic fraction, n-hile ea. 8% each appear in the acidic and oxygenated fractions (4). Aromatic compounds could be expected to constitute an appreciable percentage of these latter trvo fractions, because polynuclear hydrocarbons are well established as components of polluted atmospheres and many oxidation products of polynuclear hydrocarbons fall into these classes. A possible explanation for this low percentage lies in the fact that electronegatively substituted compounds such as aldehydes, nitro derira-
tives, and quinones do not react with piperonal chloride. Thus, many aroniatic carbonyl derivatives would not give this test; these are precisely the types of compounds to be expected as stable air oxidation products of the polynuclear hydrocarbons. This explanation is further borne out by a comparison of the infrared absorption spectra of the crude benzene extract and its fractions. A band of moderate intensity at 5.8 t o 5.9 microns in the crude material, apparently due to carbonyl compounds, is distributed among the fractions with its greatest intensity in the acidic and oxygenated portions, lesser intensity in the neutral aromatic and Tater-soluble fractions, and only minor absorption in the basic and aliphatic fractions. If these bands are in fact caused by the oxidation products of complex aromatic conipounds, some of these fractions should yield reactions characteristic of quinones. A sensitive, specific test for polycyclic quinones was developed which involves reduction in a n alkaline medium. The test can be carried out in clinietlivlforniamide, n hich iq n-eakly alkaline. Honever, if the solvent is .lightly acidified, the color reaction fails. Mildly alkaline acetone can be used a. a qolrent, but the color changes are not a; intense. The color reaction can take place irreversibly in o-dichlorobenzene or diphenyl ether, if some benzyltrimethylammonium methoxide is added to the mixture. Of the many solvents studied, dimethylformaiiiide is, by far, the best. The reduction of anthraquinone t o 9,10-dihyrlroq-anthracene in alkaline media (1, 2) is a reaction tj.pical of polycyclic p-quinones. Consequently, the niechanism of the thermochromic reaction probably involves reduction and formation of a highly conjugated anion at the boiling point. REAGENTS
All compounds were obtained from the Fisher Chemical and the Aldrich Chemical Co., or were prepared by standard literature procedures in the laboratory. Potassium borohydride was obtained from Metal Hydrides Inc., Beverly, ?.lass.
PROCEDURE
The quantity of material to be tested depends on the concentration of pquinones in the sample. For samples consisting almost wholly of p-quinones, 10 to 200 y will give excellent results. For the usual neutral aromatic fraction obtained from air particulate matter, best results were ordinarily obtained with 0.5 to 10 mg. of material. The
Table I.
Thermochromic Detection of Some p-Quinones
Compound Anthraquinone ( I ) 1-Xethylthio I 2-Methylthio I 1-Phenylthio I 7,8,9, IO-Tetrahydronaphthacene-5,12-dione 1,l ’-Dianthraquinone 1-Hydrazino I 1-lmino I 2--lmino I Sodium 2-1 sulfonate
1-Chloro I 2-Chloro I Naphthacene-5,12dione Pentacene-B,13dione Anthanthrone Benz [a] anthracene7,12-dione Xaphtho [2,3-a]pyrene-7,12dione Benzanthrone Anthronec Fluorenone 2,3-Benzofluorenone 1-Hydroxy I Dinaphtho[2,32’,3’] thiophene5,7,12,13-tetrone Dibenzo[b,i]thianthrene-5,7,12,13tetrone
Colora Cold Hot
Sensitivity, -,b
1-
4
P, I-
1-
5 5 6
R
5
l? R1-
4
RV
I?
2 6 6
r! 11-
8 25 25
B
5
R
BG
35
€3
8
B
20
B TBr R
6 2
R
5 40
G ro
200
Y
30
C
15
4
Dinaphtho[ 1,2,2’,3‘]furan7,12-dione J80 a Capital letters signify intense colors; Emall letters signify light t o pale colors. 0 = orange, V = violet, R = red, Y = yellow, B = blue, G = green, Br = bromm, and c = colorless. b Concentration limit p.p.m. is txice the numerical value of the sensitivity; for anthraquinone the concentration limit is 8 p.p.m. c The same color change is obtained without potassium borohydride.
VOL. 30,
NO. 12, DECEMBER 1958
2005
substance to be analyzed was dissolved in 0.5 ml. of dimethylformamide, 5 to 10 mg. of potassium borohydride was added, and the test tube was heated to a vigorous boil, when the color developed. Then the mixture was cooled with tap or ice water, while being vigorously shaken. The heating and cooling procedure was repeated several times, with the color noted each time a t the boiling and a t the cold stages. For a positive test a red, violet, blue, or green color is obtained a t the boiling point and a pale yellow, orange, or pink color upon cooling. I n the few cases which were investigated, the thermochromic reaction could be reversibly repeated a dozen times. Sensitivities and concentration limits are reported for various p-quinones in Table I. DISCUSSION
OF
RESULTS
Investigation of various types of compounds has disclosed that many polynuclear aromatic compounds containing the quinonoid structure, I 0
‘V’ /I 0
I show a reversible, thermochromic reaction in the color test. The only compounds not containing structure I, but giving a positive (but less sensitive) test, were fluorenone and 2,3-benzofluorenone. The fluorenone structure resembles that of structure I. These results suggest the possibility that the test may also be of some value for polycyclic fluorenones. All the tested un-
substituted polynuclear p-quinones containing structure I were found to give the reaction. Many derivatives of anthraquinones exhibit the color reaction; however, a few do not. Anthraquinone and its derivatives give red to violet colors in this reaction. The higher molecular weight polynuclear p-quinones give blue colors. Several heterocyclic p-quinones and 1-hydroxyanthraquinone underwent reversible thermochromic color reactions, wherein an intense red to violet color was present a t room temperature and a pale yellow to orange color a t the boiling point. il very large number of compounds gave negative reactions under the conditions of the test-e.g., pyranthrone, violanthrone, flavanthrone, dibenzo[a,h]pyrene-7,14-dione, 9,lO-phenanthraquinone, chrysene-5,6-dione, 1,42 - methylnaphthonaphthoquinone, quinone, 2,3-dichloronaphthoquinone, tetrachloro - p - benzoquinone, 2hydroxy - 9,lO - anthraquinone, 1,4diamino-9,lO-anthraquinone, 6,l l-dihydroxy-5,12-naphthacenedione, 5,6, 11,12-naphthacenetetrone, benzil, 9acetylanthracene, benzophenone, 2-hydroxycarbazole, Zaminobenzophenone, pyrene, 2-naphthol, anthracene, dianisylideneacetone, diphenyl sulfide, 1nitropyrene, 1-carboxyfluorenone, and 2,5-dinitrofluorenone. APPLICATIONS
Aliphatic, neutral oxygenated, and acid fractions gave negative results in the test. As 10 y of anthraquinone could be detected in the presence of 2000 y of the oxygenated fraction, this fraction must contain less than 0.5% of the p-quinonic compounds. The
intense absorption of the carbonyl band in the infrared spectrum of neutral oxygenated fractions must be due to the presence of other types of carbonyl derivatives. This fact is to be investigated. On the other hand, a minimum amount of 1.0 mg. of neutral aromatic fractions from a San Francisco air particulate sample gave a reversibly green, thermochromic reaction. Assuming a sensitivity of 10 y, this aromatic fraction would contain approximately 1% of the polynuclear p-quinonic compounds. Under the same conditions a minimum amount of 2.5 mg. of a Charleston neutral aromatic fraction gave a positive green color, while 3 mg. of a rural aromatic fraction from Tonka Bay, Minn., gave a negative reaction. From the green color it would appear that the compound or compounds giving the test must have a t least four fused rings. ACKNOWLEDGMENT
The authors gratefully acknowledge the gift of a sample of dibenzo[a,h]pyrene-7,14-dione from B. L. Van Duuren of New York University. LITERATURE CITED
(1) \ , Graebe. C.. Liebermann. C.. Ann. Chem. Liebigs 160, 127 (1871). ’ (2) Meyer, H., Ibid., 379, 37 (1911). (3) Sawicki, E., Stanley, T. W., Miller, R. R., Hauser, T. R., ANAL. CHEM. 30, 1130 (1958). (4) Stanley, T. W., Sawicki, E., unpub-
lished research.
(5) Tabor, E. C., Hauser, T. R., Lodge,
J. P., Jr., Burttschell, R. H., A . M . A . Arch. Ind. Health 17, 58 (1958).
RECEIVED for review March 19, 1958. Accepted July 29, 1958.
Estimation of Boron-1 0 Burnup by Flame Photometric Lithium Determination DRAGOMIR DUTINA
Co., Schenectady, N. Y
Knolls Atomic Power laborafory, General Electric
b In connection with the burnable poison and control rod program, it became necessary to estimate the burnup of neutron-irradiated steel, zirconium, and Zircaloy alloyed with boron-10. A method is described in which the burnup is measured by determining with a flame photometer the lithium produced by means of the boron-1 0 (n,cu) lithium-7 reaction. An ammonia precipitation of the hydrolyz-
2006
ANALYTICAL CHEMISTRY
able radioactive materials is carried out remotely and reduces the radioactivity sufficiently to permit the lithium analysis of the filtrate with ordinary laboratory handling methods.
T
o
TEST the effect of neutron bombardment on burnable poison and control rod materials such as alloys of zirconium-boron-10, Zircaloy-boron-10,
and steel-boron-10, accurate burnup values were required. As the neutron flux values were not known with sufficient accuracy t o permit calculation of boron-10 burnup, an empirical determination became necessary. Several methods of determination based on the boron-10 (n,a) lithium-7 reaction were possible. For example, mass spectrometric determination of the boron-11-boron-10 ratios before
