652
INDUSTRIAL AND ENGINEERING CHEMISTRY
order to obtain an angle of 70’ for illumination and viewing inside of the box. The cross-sectional area of the illuminating beam is approximately 12 sq. cm. A null method by which the readings will be obtained directly in terms of the secondary standard, independent of intensity fluctuations of the light source, will be employed. Considerable data are being accumulated on the relation between the relative apparent reflectance in the direction of mirror reflection for a given illumination and the least perceptible visual differences throughout the gloss range.
Summary Previous investigators have attempted t o correlate socalled “gloss” measurements of surfaces with visual observations of the surfaces. Inherent gloss, however, is only one factor in the appearance of a surface and in order to measure it, i t is necessary to prepare paint films such that the inherent gloss is the only factor in the measurement. A refined method of preparing paint surfaces for measurementnamely, doctor-blading on plate glass-is introduced to control or eliminate extraneous factors affecting goniophotometric measurements and visual observations of inherent gloss. The construction of a goniophotometer for research
VOL. 12, KO. 11
work on gloss in the finishes field and other fields is described and complete specifications are given. Finally, for control work in the case of high and semigloss finishes, the relative apparent reflectance in the direction of mirror reflection for unidirectional illumination a t 45 ’ should be measured, the aperture sum not to exceed 2.5’. For eggshell and flat finishes, the relative apparent reflectance in the direction of mirror reflection for unidirectional illumination a t 67.5’ should be measured, the aperture sum not to exceed 2.5’.
Literature Cited (1) Commission Internationale de l’Eclairage, Cambridge, Proceedings of 8 t h Session, pp. 19-29, Sept., 1931. (2) D r u d e , P., “Theory of Optics”, New York, Longmans, G r e e n a n d Co., 1920. (3) R a n s t o c k , R. F., J . Oil Colour Chem. Assoc., 20, 91 (1937). (4) H u n t e r , R. S., J . Research Natl. B u r . Standards, 18,19 (1937). (5) H u n t e r , R. S., a n d J u d d , D. B., P a i n t V a r n i s h Production J f g r . , 19,152-9, 176-8 (1939). (6) Jones, L. A., J . Optical S O C .Am., 6 , 140 (1922). (7) McNicholas, H. J . , J . Research LVatl. B u r . Standards, 1, 29 (1928); 13,211 (1934). (8) P r e s t o n , J. S.,Trans. Optical SOC.(London), 31, 15 (1929-30).
PRESENTED before the Division of Paint and Varnish Chemistry a t the 9Sth Meeting of the American Chemical Society, Cincinnati, Ohio.
Detection and Estimation of Dihydrorotenone In the Hydrogenation Products of Rotenone LYLE D. GOODHUE AND H. L. HALLER Bureau of Entomology and Plant Quarantine, U. S . Department of Agriculture, Washington, D. C.
Among the numerous derivatives of rotenone thus far studied, only dihydrorotenone retains the high insecticidal action of the parent compound. The apparently greater stability of this derivative has led to its commercial production. Catalytic hydrogenation of rotenone produces, in addition to dihydrorotenone, the nontoxic hydrogenation products rotenonic acid, dihydrorotenonic acid, and dihydrorotenol. To develop a method for the deter-
AiSY derivatives of rotenone have been prepared in the course of studies on its structure, and some of them have been tested to determine their insecticidal action. K i t h the exception of dihydrorotenone, they have been found to be of little value as compared with the parent compound. Dihydrorotenone possesses about the same toxicity to insects as rotenone (11), and i t may be somewhat more stable to oxidation in the presence of light ( 8 ) , although further experimentation is desirable on this subject. Dihydrorotenone (formula 11, page 653) is prepared by catalytic hydrogenation of rotenone (I) with Raney nickel or the reduced platinum oxide catalyst. Under proper conditions the saturation of the double bond in rotenone proceeds readily, with the formation of dihydrorotenone in good yield. However, for reasons not yet fully understood, the hydrogenation sometimes takes another course and rotenonic acid (isodi-
mination of dihydrorotenone in the mixture of hydrogenation products, some of the physical and chemical properties of these compounds were examined. A combination of physical properties will give some information as to the amount of dihydrorotenone present, but a better method is based on the observation that this is the only reduction product giving an appreciable red color by the Goodhue test. The proposed method is based on this test.
hydrorotenone, 111) is obtained. This compound differs from dihydrorotenone in that the oxygen bridge of ring E is cleaved and the double bond remains unsaturated. On continued hydrogenation the double bond is saturated, with the formation of dihydrorotenonic acid (tetrahydrorotenone, IV). These two compounds are the most common by-products formed in the preparation of dihydrorotenone. I n one instance, however, where a special nickel catalyst was employed, the reduction product consisted almost wholly of dihydrorotenol (V) (6). Some of the physical and chemical properties of all four hydrogenation products have been described, but no procedure has been proposed for their detection or estimation in the presence of each other. Since dihydrorotenone is now commercially available, further study of the compounds was undertaken, and this paper describes a method for the detec-
ANALYTICAL EDITION
NOVEMBER 15, 1940 TABLE I.
653
ROTENONE .4ND HYDROGENATION
SOME PHYSICAL AXD CHEMICAL PROPERTIES O F
Melting Point
Compound
163 216 209
Dihydrorotenonic acid
216
Dihydrorotenol a Jones and Smith ( 9 ) . b Haller and LaForge (6). C LaForge and Smith ( I O )
131
FORMED BY ITSCATALYTIC
--
Solubility I n isoGoodhue propanol value G.1100 c c . G . / l G G cc. 8.0" 0.2" 100 6.3 0.2 92 0.5 3.9 6
7
7
c.
Rotenone Dihydrorotenone Rotenonic acid
Specific Rotation I n Benzene I n Chloroform Concn. [el% Concn. Degrees G.liGO cc. Degrees G./lGG c c . - 230a 2 - 116a 2 -223.0 2.5 - 123.Z b 5 5 4- 3 6 . D 2.1 4- 45.Ob 6 9 45.5 2.1 ... 67.0b 7.7 53.2 2.2 -100.7 3.1 74.4 3.1
THE PRODUCTS
[e]%
...
...
++ + -
tion and estimation of dihydrorotenone in the presence of rotenonic acid, dihydrorotenonic acid, and dihydrorotenol.
Experimental
PREPARATION OF MATERIALS.The compounds used were obtained by the catalytic hydrogenation of rotenone according to the procedure already described (6, 7 , IO). The main product, dihydrorotenone, was separated from acidic substances by means of alkali and purified by crystallizing twice from carbon tetrachloride and twice from ethanol. Only the high-melting form (216" C.) mas obtained. (The melting points recorded throughout this paper are corrected.) If the reduction is interrupted after the absorption of one mole of hydrogen per mole of rotenone, the acidic product is rotenonic acid. It was separated from the dihydrorotenone as mentioned above and purified by crystallization from ethanol until a constant melting point (208" C.) was obtained. When rotenone is allowed to absorb more than one mole of hydrogen, a considerable quantity of dihydrorotenonic acid is formed together with dihydrorotenone and rotenonic acid. The mixture of the two acids, after the removal of dihydrorotenone, was separated by isomerizing the rotenonic acid to beta-dihydrorotenone (4), which is insoluble in alkali. The dihydrorotenonic acid, recrystallized three times from methanol, melted a t 216" C.
In benzene
Crystal Shape Hexagonal Wedge-shaped Seedles Seedles
0.4
4.0
5
Needles
15.6
0.3
1
The dihydrorotenol used in these tests was obtained by hydrogenation of rotenone in butyl acetate solution with a special nickel catalyst (6). It was purified by recrystallization from ethanol until the recorded melting point (131" C.) was obtained.
.
DETECTION AKD POSSIBLE DETERMINATION BY USE OF PHYSICAL COXST-4KTS. Some of the most easily determined physical constants that might be used in the detection or estimation of these compounds have been examined. Those already reported in the literature were checked and, together with values determined by the authors, are assembled in Table I. Data on rotenone are included for comparison (9). The corrected melting points, the crystalline forms, and the specific rotations were determined by the usual methods. The specific rotation of rotenonic acid and dihydrorotenonic acid could not be determined accurately in benzene because of low solubility. I n chloroform the values obtained by the authors do not check the recorded values (9, IO), but a variation was expected since alkali, which racemizes these compounds, was used a t one stage in the purification. The positive rotation, however, is a distinguishing characteristic. The solubilities in benzene and isopropyl alcohol st 25" C. were determined by weighing the residue, dried a t 105" C., from 2 or 5 cc. of saturated solution of each compound. Dihydrorotenone is considerably more soluble in benzene than are the acid derivatives, and a simple distinguishing test
454
IXDUSTRIAL AKD ENGIKEERISG CHERlISTRk
10L. 12, NO. 11
(c) -$ solution made by dissolving 40 grams of potassium hydroxide in 100 cc. of water. (d) 4 n alcoholic potassium hydroxide solution containing sodium nitrite prepared immediately before use by mixing 7 volumes of ( b ) and 1 volume of (c). ( e ) A commercial grade of acetone that is comparatively free of water and gives a clear, colorless blank. Solutions ( a ) , ( b ) , and (c) keep for long periods, but solution ( d ) will not keep for more than 1 day. 0 = SUPPLEMENTARY SOLmlON PROCEDURE. A standard solution is prepared by weighing accurately approximately 20 mg. of pure dihydrorotenone and making up to 100 cc. with acetone. A solution of the unknown is also made in the same way with approximately 20 mg. of material to 100 cc. of acetone. This weight should be doubled if the dihydrorotenone in the mixture is known to be below 50 per cent. Two cubic centimeters of acetone are pipetted into a test tube for a blank and 1 cc. into each of four other tubes. Into two of these tubes 1 cc. of the standard is pipetted and into the other two 1 cc. of the unknown, and 2 cc. of the alcoholic potassium hydroxide containinu sodium nitrite (d) are added to all the tubes. The solution is nipxed immediately and allowed to stand at room temperature (approximately 25" c.) for 5 minutes. Six cubic centimeters of the 1 to 3 sulfuric acid ( a ) is then added, mixed immediately, and placed in a beaker of cold water (15' to 20" C.). After about 5 minutes the tubes are removed from the batli, brought to room temperature, and compared in a suitable instrument. The use of a photometer has been found to be the most accurate method of comparing the st'andards and the unknowns. The colors can be developed directly in selected test tubes nhich 0.15 0.20 0.25 0.30 fit the photometer, or they can be developed in any test tube MG. OF DIHYDROROTENONE and poured into a special cell. A Brice ( 1 ) photometer which gives percentage transmission as direct readings has been found FIGCRE1. GRAPHIC METHODO F TR.4NSLATING LIGHT TRANSMISSION INTOMILLIGRAMS OF DIHYDROROTENONE satisfactory. Glass filters (Corning, 3.5 mm., KO.430, dark shade blue green) were used. The blank is taken as 100 per cent transmission, and the photometer is therefore adjusted to give a reading of 100 with the cell containing the blank in place. The for these compounds in a mixture is powible since there is readings for the standards and unknowns ~ h i c hare next oblittle mutual-solubility effect. This effect v a s determined by tained are therefore in per cent transmission. weighing the residue from 5 cc. of benzene saturated with both Since the color for rotenone has been found by Cassil (undihydrorotenone and rotenonic acid. A solubility of 7.8 published) to follow Beer's law, there is eyer$ reason to begrams per 100 cc. of solution was obtained as compared with lieve that the results will be the same with dihydrorotenone. 6.3 grams for the sum of the two solubilities determined sepa-4plot is therefore made on semilogarithmic paper with transrately. This mutual-solubility effect was further studied by mission as ordinate (logarithmic) and concentration as abdetermining the amount of a mixture of dihydrorotenone, scissa (arithmetic), and a straight line is drawn from the point rotenonic acid, and dihydrorotenonic acid that is required of zero concentration and 100 per cent transmission to the t o saturate benzene. h solubility of 7.7 grams as compared point determined by the concentration and the transmission with the sum of the separately determined solubilities with of the standard. The transmission of the unknown having 7.2 grams per 100 cc. was obtained. been determined, its concentration can be read from the COLORIMETRICDETERJII~-.~TIOS. The physical data just curve and the percentage calculated. Such a curve is ilgiven can be used qualitatively, or in some cases semiquantitalustrated in Figure 1. tively, t o determine the hydrogenation products that are formed, but a more accurate and definite method of analysis A determination vas made witli a standard solution containing 0.23 mg. of dihydrorotenone per cc. and another supplementary for dihydrorotenone is desirable. The Goodhue (3) modifica?elution containing 0.115 mg. of dihydrorotenone and 0.115 mg tion of the Gross and Smith colorimetric method for the deterof rotenonic acid per cc. After adjustment to the blank the mination of rotenone and deguelin was tried, since it has been :&veragereading For the standards was 22.8, and for the others it vas 47.2. A straight line was then drawn from the point of zero found that several of the toxic compounds present in derris mncentration and 100 per cent transmission t o the point detergive a red color by this procedure. Of the four hydrogenamined by the concentration and a transmission of 22.8 per cent. tion products only dihydrorotenone gave a color approaching From this curve and the reading for the supplementary solution, t h a t given by rotenone. The amount of red color compared 47.2, a value of 0.11.5 n-as obtained. This also illustrates the neglirible effect of rotenonic acid in this determination. with rotenone as 100, Goodhue value ( 2 ) , for each of these compounds is given in Table I. Literature Cited Since the color ralues obtained with rotenonic acid, dihydroBrice. B. A.. Rev. Sci. Instruments. 8. 279 11937). rotenonic acid, and dihydrorotenol are negligible compared Cahn, R.S., Phipers, R. F., a n d B o a m , J.'J., J . Suc. Chem. Id., with those obtained with dihydrorotenone, i t is possible to 57, T200 (1938). use the reaction for the determination of the last-named Goodhue, L. D., J . Assoc. Oficial A g r . Chem., 19, 118 (1936) compound in a mixture of the materials. As the procedure Haller, H . L., J . Am. Chem. Soc., 53, 7 3 3 (1831). Haller, I€. L., a n d LaForge, F. B., Zbid., 53, 3426 (1931). described for carrying out the color test has been improved, Haller, H . L., a n d Schaffer, P. d., ISD. ESG. CHEU., 25, 983 the details of the modified method are given here with special (1933). reference to the determination of dihydrorotenone. Haller, H. L., a n d Schaffer, P. d . , J . A m . Chem. S o c . , 55, 3494
(1933).
REAGEKTS (a) A dilute sulfuric acid solution prepared by mixing 1 volume of concentrated sulfuric acid vith 3 volumes of nater. The sulfuric acid should be free from nitrous acid. (a) An alcoholic solution of sodium nitrite prepared by dissolving 1 gram of sodium nitrite in 10 cc. of nater and diluting to 1 liter with 95-100 per cent ethanol.
Joncs, H. A , Gersdorff, IT. .I.,Gooden, E. L., C a m p b e l l , F. L . , a n d Sullivan, IT. S . ,J . Econ. Entomol., 26, 451 (1933). Jones, H. A , , a n d S m i t h , C . 31.,J . Am. Chem. Soc., 52, 2554 (1930). LaForge, F. B., a n d Smith, L.E., Ibid., 51, 2571 (1929). Sullivan, IT. N., Goodhue, 1,. D., and Haller, H. L., S o a p , 15 (7), 107 (1939).
