ANALYTICAL CHEMISTRY
1954 Table VI.
Analyses of Dewaxed Lubricating Oil Base Stocks
Composition, Volume 7p rlverage Known 0 Found Molecular SatuOleMonoPolySatuOleMono; PolyWeight rates fins aromatics aromaticsb iates fins aroniatics aromatics b 340 6F 11 11 9 66 14 7 13 390 60 1 14 25 60 0 12 28 400c 48 0 15 37 46 0 13 41 420 61 0 19 20 60 0 23 17 440 61 0 17 22 60 0 18 22 450 58 0 14 28 55 0 18 27 460 46 0 14 40 46 0 13 41 a .4ccuracy of “known” values, i l to 2%. b Including diaromatics and resins. C Owing t o presence of dark products of oxidation, isopropyl chloride was used as eluent in this case.
alternative that naturally comes to mind would be the determination of saturates by acid absorption, olefins by halogenation, and aromatics by difference. As might be expected, however, this approach fails because the olefin-aromatic ratio so obtained is entirely erroneous. This may be illustrated by the results of a cooperative testing carried out by several laboratories with the lightest of these oils, the thermally cracked gas oil of boiling range 170” to 310” C. (see Table V). Its true composition is considered accurate to within & l % . This oil is still light enough for determination of saturates by acid absorption to within 1 or 29; of the known value of 487,. Bromine numbers by various methods ranged from 31 to 38 grams per 100 grams. In calculating the olefin content from these bromine numbers by aid of the determined molecular weight of the sample, 191, one obtains values of between 37 and 45% as compared with the known value of 167,; this leaves only 8 to 16% for the aromatics, *the known content of which is 36%. With the FIA method the same laboratories obtained results which, on the average, deviated from
the known values by only -1.9, -0.5, and +2.4% for saturates, olefins, and aromatics, respectively. 4CKNOWLEDGMENT
The authors are indebted to R. E. Thorpe, R. E. Murdock, T. Skei, and A. G. Polgar for preparation of the reference samples. LITERATURE CITED
( I ) Am. SOC.T e h i g Materials, Philadelphia, Pa., “ASTI1 Standards on Petroleum Products and Lubricants,” D 1319-55T. . 20, 725 (1948). (2) Conrad, h.L., ~ A L CHEW (3) Criddle, D. W., Le Tourneau, R. L., I b i d . , 23, 1620 (1951). (4) Fred, >I Putscher, ., R., Ibid., 21, 9 0 0 (1949). (5) Haak, F. A , , Nes, K. van, J . I n s t . Petroleum T e c h i d 3 7 , 245 (1951).
(6) Karr, Clarence, Jr., Weatherford, W. D., Jr., Capell, R. G., . l s . 4 ~ . CHEU. 26, 252 (1954). (7) Knight, H. S., Skei, Thurston, Groennings, Sigurd, Sixon, A. C., Ibid.. 28, 8 (1956). (8) Smit, W. M., Discussions F a r a d a y Soc. 7, 248 (1949). RECEIVED for review June 8, 1956.
Accepted August 20, 1956.
Full luminescence at liquid-Air Temperature of Methyl-l,2benzanthracenes and Methyl benzo[c] phenanthrenes YEHUDA HIRSHBERGI Daniel Sieff Research Institute, Weizmann lnstitute of Science, Rehovoth, Israel
A t liquid-air temperature, in a mixture of solvents which sets to a rigid clear glass, the full luminescence of the monomethyl derivatives of the methyl-l,%-benzanthracene and methylbenzo Iclphenanthrene series shows distinctive spectra in relation to that of the parent compound. The significant changes in the spectrum caused by the introduction of the niethjl group in different positions can be used for the identification of any methj 1 derivative of 1,2-benzanthracene or benzo [clphenanthrene. The afterglow of the most carcinogenic compounds of the benzanthracene series is specifically different from that of all the other members of these series.
I
3 2A-4
1
S ACCORDAKCE with the reversible nature of absorption
and emission of light it has been found that groups of compounds produce characteristic patterns of fluorescence spectra. On this basis biologically active polycyclic hydrocarbons have been ident,ified by fluorescence spectrography in the past 20 years I
( I , 2, 4, IO). Because the accuracy of the fluorescence data depends on the sharpness and fine structure of the bands, better results may be obtained when the fluorescence is studied at low temperatures. In the case of the methyl derivatives of 1,2-benzanthracene ( I ) and benzo [clphenanthrene (XV) the methyl position has little influence on the fluorescence spectra of the parent hydrocarbons a t room temperature.
Present address, Gnirersity of California, Berkeley 4 , Calif.
I The benzanthracenes and the benzo [clphenanthrenes are sensitive to ultraviolet irradiation ; therefore, when their fluores-
V O L U M E 28, NO. 1 2 , D E C E M B E R 1 9 5 6
1955
Its spectrum consists of three bands, two of them of relative medium intensity with maxima a t 4130 and 4360 A. When dissolved in a mixture of ethanol plus methanol plus ether (8 to 2 to 1 by volume) which sets a t liquid-air temperature to a rigid clear glass, the luminescence is of a strong bluish color and has a brick-red afterglow of about 0.5 second. The spectrum consists of 14 well defined bands. Five of the first eight bands, which belong to the singlet+ singlet emission, are intense, having maxima a t 4070 -4.[ l ] ,4100 A . [2], 4160 A . [3], 4310 A. [4], and 4600 A . [5], tn-o bands are of about half the intensity of the latter, having maxima a t 4810 A . [B], and 4920 A . [7], and there is n weak one a t 5200 A. [SI. The triplet -, singlet emission is presented by the six remaining bands with maxima a t 5740 A . [e], 5980 A . [lo],El00 A . [ l l ] ,6220 .4.1121, 6340 A. [13], and 6450 .4. [14]. The most intense band of the afterglow is the tenth one (I, Figure 1). although the luminescence and the afterglow of most of the methyl derivatives of 1,2-benzanthracene seem visually to be the same as those of the parent compound, different significant changes in the spectrum of each methyl derivative show that the methyl position in 1,2-benzant2ii~acenemay be identified in this nay. The maxima and the relative intensities of the full luminescence band of l,2-benzanthracene and its most important methyl derivatives are presented in Figure 1 and Table I . The methyl group introduced into position 1 (compoiind 11) causes a hypsochromic shift of maxima [ I ] , [21, [31, [51, [8] [IO]. [ I l l , and [14], and the disappearance of bands [GI, [7], [9], [12], and [14]. At the same time, the intensities of the maxima of the afterglow bands [ l o ] , [ l l ] ,and [13] are strongly reduced (compare I1 with I in Figure 1). I n the case of the 2-methyl derivative (111) there is a bathochromic shift in the maxima relative t'o those of derivative I1 and the spectrum of I11 is distinguished from that of the parent, hydrocarbon in that bands [6], [TI, [9], [ 121, and [ 131 are absent in the former and in the strongly reduced intensities of [ l o ] , [ I l l , and (14) (compare I11 with I1 and I in Figure 1). When the methyl group is in position 3 (compound IT') the spectrum differs from I in that bands [6], [?I, 181, [91, [12], and [13] are absent in the former; the maxima 111, [2], [ 3 ] , [4], [5]! [IO], and [ l l ] are hypsochromically shifted relative to those in IT1 and [SI is absent; and its spectrum is bathochromically shifted relative to that of I1 (compare IT with I, 11, and I11 in Figure 1). The spectrum of the $-methyl derivative ( V ) is dist~inguished from those of all the former methyl derivatives by the reappearance of bands [7], [9], and [12] and by the higher intensities (compare 5' with I, 11, 111, and 15' in Figure 1). The strong hypsochromic shift of maximum [ l ] and the strong bathochromatic shift of maxima [7], [8], [9], [ l o ] , [ l l ] , [12], and [14] in relation to those of the parent hydrocarbon are helpful in distinguishing between the spectrum of V and that of I (compare 'I: with I in Figure 1). The spertiiim of the 5-methl-1 derivative (VI) differs fioni those
cence is studied a t room temperature, not only is a loss of reradiative power of the light-absorbing molecules caused by thermal collisions, but the photochemical process produced by the ultraviolet-exciting light disguises the fluorescence. At liquidair temperature the compounds are more stable toward irradiation, thermal collisions are minimized, and the fluorescence spectra are sharper. I n the full luminescence spectrum a t liquidair temperature, not only the bands of the singlet -, singlet emission (fluorescence) appear, but also the triplet --c singlet emission (phosphorescence) is recorded (6, 8); therefore the spectrum of each methyl derivative is more detailed and distinctive. Although the fluorescence and phosphorescence of some of the compounds reported in this paper have been studied at liquid-nitrogen temperature ( 5 , 9, 11, l a ) , no systematic investigation of the full luminescence of all the monomethyl derivatives of 1,2-benxanthracene and benzo [c ]phenanthrene has been recorded. This paper shows that the significant changes in the full luminescence spectra of the parent polycyclic hydrocarbons, caused by the introduction of the methyl group in different positions, can be used to identify any methyl derivative of 1,2benzmthracene (I) or benzo [c]phenanthrene (XV). EXPERIMEBTAL
All the compounds investigated were kindly sent by Melvin S. SeRman, Ohio State University. Solvents. Pure absolute ethanol and methanol were prepared by the usual methods. Dry ether was purified by passing it through a column of activated silica gel. The rigid clear glass formed by the mixture of ethanol plus methanol plus ether (in proportions of 8 to 2 to 1 by volume) a t liquid-air temperature had no luminescence Apparatus. T o measure the full luminescence and the afterglow of the compounds studied, an apparatus was constructed similar to that described by Farrow, Reckers, and Germann ( 3 ) . The apparatus (3, Figure 3 ) consists of a blackened, lighttight iron box containing a quartz Dewar flask and the sample. On one side of the box, two gear-driven synchronous shutters are mounted so that the surface of the sample that is excited by ultraviolet light may radiate the luminescent or phosphorescent light directly to the slit of the spectrograph, with a minimum loss due to absorption or reflection. I n order to photograph the full luminescence spectrum of a compound, the shutters are held stationary and both are open a t the same time. To photograph the phosphorescence, one shutter is placed a t 90' out of phase with the other and both are driven by a '/s-hp. motor up to speeds of 3450 r.p.m. I n this arrangement, the surface of the sample was excited by the 3560 A. group of a General Electric mercury arc (Type A-H6). The angle between exciting and luminescent radiation was about 45'. Luminescence and Phosphorescence Spectra. These 1% ere photographed with a Fuess glass spectrograph on Kodak P1500 2.5 x 3.5 inch panchromatic plates and evaluated by means of a Leeds 8: Northrup recording microphotometer. The slit of the spectrograph was held a t a constant width of 0.1 mm. and the time of exposure for all the compounds studied was 15 minutes. RESULTS AND DISCUSSION
Monomethyl-1,Zbenzanthracenes. At room temperature the fluorescence of 1,2-benzanthracene (I) is of a weak violet color.
Table I. C:ompouxid
I I1 I11 Is' T'
VI VI I
VI11 IX X
XI XI1 XI11 XIV
Maxima (in A.) of Bands of Full Luminescence Spectra of 1,Z-Benzanthracene and Its Methyl Derivatives 1 4070 3980 4085 4060 4010 4020 4000 4080 4070 4020 3990 4030 4100
2 4100 4070 4120 4100 4110 4120 4070 4120,4150 4110 4110,4145 4100 4080,4125 4165
3 4160 4100 4210 4150 41.50 ~~.
4150 4110 4220 4160 4190 4140 4190 4210 4270
4 4310 4320 4340 4320 4370 4390 4330 4370 4330 4340 4360 4330,4370 4430 4520
5 4600 4560 4600
6 4810
7 4920
8 5200 5040 5270
9 5740
4980 4960 4960 4950
5260
5790 5710 5680 5390
,.
4,591) ....
4620 4620,4660 4600 4590,4630 4600 4550,4600 4620 4520,4550 4690 4800
48io 4820 4810
5080
5140
5380 5240 5230 5270 5200 5250 5300 5580 5500
.. ..
5720 5670
11 6100 5900 6080 6050 6200 6100 6120 6i40 6080 6060 6120
12 6220
.. ..
13 6340 6280
14 6450
6140
6420 6420 6570 6490 6500 6440 6500 6520 6500 6520 6500 6570
6300 6170 6200
siio 6180
..
6iiO 6460
6410 6i60
ANALYTICAL CHEMISTRY
1956 of all the former compounds in the splitting of band [5] into two bands, [Sa] and [jb], while there is a bathochromic shift of maxima [4] and [5] (compare VI, with I, 11, 111, IV, and V in Figure 1 ) . The afterglow of compound VI is tivice as long as that of each compound described above. The 6-methyl derivative (compound VII) can be identified by the reappearance in its spectrum of band [6] and the disappearance of band [ I ] . The maxima of its phosphorescence are of much higher intensities than those of the former compounds (compare VI1 with I to VI in Figure 1). 7-Methyl-1,2-benzanthracene (VIII) is distinguished from the compounds described above by the fact that its afterglow is of such short duration that it is not perceived visually. I n its spectrum, bands [2] and [5] are split into two bands [2al, [2b], [5a], [5b]; bands [6], [ll],and [12] arenot present, and there is a strong hypsochromic shift in maxima [e], [lo], [13], and [14] (compare VI11 with I t o VI1 in Figure 1). While the spectrum of the %methyl derivative ( I X ) is similar t o that of the parent compound (I), the absence of bands [ 7 ] , [9], and [13] allows a distinction between them. T h e brick-red afterglow of IX is twice as long as in the case of I, 11, 111, IV, and V (compare IX with I in Figure 1). I n the spectrum of the 9-methyl derivative (X), seven bands appear instead of the first five bands; therefore compound X is easily differentiated from all the former compounds (compare X n i t h I to I X in Figure 1). Although the spectrum of lO-methyl-l,2-benzanthracene ( X I ) is similar t o that of compound 11, the fact that all its maxima are bathochromically shifted with regard to those of I1 and its afterglen- half as long as that of I1 makes it possible to distinguish between them (compare X I with I1 in Figure 1). The spectrum of the 11-methyl derivative ( X I ) has eight bands instead of the first five appearing in the spectrum of the parent compound ( I ) . This distinguishes the spectrum of compound SI1 from all the others described (see XI1 in Figure 1). The spectrum of the 12-methyl derivative ( X I I I ) is easily recognized by the strong bathochromic shift of maxima [2], [3], [4], [SI,[i] , and [8] in relation to the corresponding maxima of all the former compounds (sre SI11 in relation to I to 911 in Figure 1). In the case of XIII, which is stiongly biologically active, like compound VIII, the afterglow has a short life and is not perceivable visually as in the case of the latter. The full luminescence of i,l2-dimethyl-l,2-henzanthracene (XIV) is presented in this paper, beCause this compound is the most biologically active in this series. The luminescence of SIT' will help in the discussion which follows on the correlation betn-een luminescence and biological activity. The three most carcinogenic of the methyl derivatives of the 1,2-benzanthracene series (derivatives VIII, XIII, and XIV) are distinct from all the others, in that the triplet + singlet emission (the afterglow) of each is of short duration and is not visually perceivable, whereas all the other methyl derivatives have a relatively long phosphorescence. In this respect compounds rrIII, XIII, and S I V resemble the best known polycyclic carcino-
-
60 20
-
4
3
2
1
5
I
I
-20 -
-
7
8
12
14
Sb 5 0
3
6
14 13 I
12 ' 1
IO
I I
I
--
1
I
8
I
I
L 60
20
60
20 60
-
-
-1 4
3 2
5
20-
60
xm
-x
2b
60
-
-Ip
I
-
IO
I4
II
--
--In
I---
IO
14
a
I
I
I 4
3 . 2 -
I
5
13
---
II
I
p
-
0 I
4
I -
3 2 I
7
IO 14 13 12 II
20
I
6500
I I
8
9 I
-
6
I
I
6000
5500
I
I
I
I
5000
4500
4000
k in A. Figure 1. I. 11. 111 I V, V. VI. 1-11,
JIaxima and relative intensities of full luminescence bands of 1,2-benzanthracene and its methyl derivatives 1,2-Benzanthracene (,l,?-BA) I-lIethyl-l,2-BA I-hlethyl-l,2,-BA 3-Met hyl-1 ,2-BA l-lIethyl-1,2-B.4 5-Llethyl-1.2-BA G-Methy1-1,Z-Bh
VIII. IS. X. SI. XI.
SIII. XIY.
7-lIethyl-l,Z-B.4 B-Methyl-l,2-B.4 9-hlethyl-1.2-BA lO-~Iethyl-l,?-BA 11-Methyl-l,?-BA 12-Methyl-1.2-B.4 7,lS-Dirnethyl-l,2-B.I
V O L U M E 2 8 , NO. 1 2 , D E C E M B E R 1 9 5 6
1957
Table 11. 3Iaxima (in A.) of Bands of Full Luminescence Spectra of Benzo(c)phenanthrene and Its RIethyl Derivatives Compound
1
7
3
4
5
6
7
8
9
10
11
XV XVI XVII XVIII XIX XX XXI
4070 4070
4170 4130 4110 4120 4130 4130 4140
4195 4180 4190 4210 4230 1215,4240 4240,4260
4290 4290
4110
4150 4530 4450 4460 4490 4480 4490
4960 5120 5010 5040 5040 5040 5030
5080 5260 5100 ,5150 5160 5170 5150
5370
5020
5800 5830 5880 5910
4070 4050 4070 4010,4090
..
.,
. .. .. .. .. ..
5610 3iiO
..
5460 3170 5470 5470
5kiO .,
,.
5920 5930 5920
bands of the shortest Tvave lengths are connected with the singlet singlet emission of the compound and the remaining seven bands are due to the triplet -+ singlet emission, the afterglor. The introduction of a methyl group in position 1 (XVI) changes the luminescence to a IT-hitish rose color and the pellowish green aftergloiv has a shorter lifetime, about i seconds. I n the spectrum the changes are represented by the different spacing of the first three bands, by the absence of bands [6]and [ 9 ] , and by a strong bathochromic shift of maxima [6], [i],and [8] (compare XVI with ST' in Figure 2 ) . When the methyl group is in position 2 (XVII) a very strong n-hite luminescence appears, having a strong yellow afterglon of a lifetime tv-iee as great as in the case of XVI. The spectrum of S V I I is distinguished from those of XT' and XVI by the disappearance of bands [ l ] , [4], [ 5 ] , and [lo] (compare SF7II with SV and X U in Figure 2 ) . I n the case of 3-methylbenzo [clphenanthrene (XVIII) the luminescence is grayish white and it has a strong greenish yel1oTT aftergloiv. Its spectrum can be recognized by the reappearance of band [I]and disappearance of bands [ A ] , [ 5 ] , and [ l o ] . Bands [9] and [ l l ] are bathochromically shifted with regards t o those of all the former benzo [clphenanthrenes (compare S V I I I n-ith S V , XT?, and S V I I in Figure 2). The 4-methj-l derivative ( S I X ) has a strong white luminescence and a green afterglon- of about 16 seconds. Its spectrum lacks bands [4]and [ 5 ] and there is a reappearance of band [ l o ] (compare XIS with S Y to S V I I I in Figure 2). \Then the methyl group is in position 5 of benzo [clphenanthrene (derivative X I ) , although its luminescence and afterglow are visually like those of X I S , the spectrum of XX is different from that of the former in the splitting of band [3] into two bands and the absence of barid [lo] (compare XX Tvith X I X in Figure 2). The luminescence of 6-methylbenzo [clphenanthrene S S I is also visually similar t o those of SIX and SS,but the spectrum of 1x1 is distinct from that' of SS in the appearance of an extra band in the beginning of the spectrum, l a (compare SSI with XIS and SS in Figure 2). +
6000
5500
5000
45'00
40b0
+ X in A. Figure 2. 3Iaxinla and relative intensities of full luminescence of benzo(c)phenanthrene and its monomethyl derivatives XV. Benao(c)phenanthrene [B (c)Ph 1
XVI. XVII.
l-AfethLl-B(c)Ph 2-Methyl-B (c)P h
XXI.
&Met hyl-B (c) P h
XVIII. 3-XIethyl-B(c)Ph XIX. 4-liethyl-B(e)Ph XX. S-hIethyl-B(c)Ph
genic hydi ocarbons, 3,4-benzopyrene and 20-nieth>lcholanthrene. This important fact has not been mentioned by othei investigators, although they have discussed the corielation between biological activity and the chemical and physical properties of these series (1, 5 , 7 , 9, 12). Monomethylbenzo [clphenanthrenes. The maxima of the bands and the relative intensities of the full luminescence spectra of benzo [clphenanthrene (XV) and its monomethyl derivatives are presented in Figure 2 and Table 11. At room temperature the fluorescence of benzo [clphenanthrene (XV) is violet: its spectrum consists of one broad band x i t h a ma.;imum a t 4230 -4. I n the rigid glass medium a t liquid-air temperature its luminescence is strong grayish I-, hite and it has a strong greenish yellow afterglow of about 10 seconds. Its full luminescence spectrum consists of 11 bands. The first si.;
ACKNOWLEDGMENT
The aut,hor is deeply indebted to Melvin S. Sewman, Ohio State University, for all the samples investigated and t o Selly Caste1 and Mosheh Iiaganowitch for their valuable technical assistance. LITERATURE CITED
(1) Berenblum, I., Schoental, R . , J . Chem. Soc. 1946, 1017. (2) Cook, J. W., Hewett. C. L., Hieger, I. J., Ibid., 1933,395. (3) Farrow, JI., Reekers. R.. Germann, F. E. E., Report to Office of Kava1 Research, Contract N6-onr-231 (1951). (4) Hieaer, I., Biochem. J . 24. 505 (19301. (5) Il'ina, A. h.,Shpol'skii, E'. Y.,Izcest.'Abed. SaukS.5.S.R.. Ser. Fiz. 15. 585 (19511. (6) Kasha, lI.,Che'na. Rkrs. 41, 401 (1947). ( 7 ) Kofahl, R. E., Lucas, H. J., J . Am. Chem. Soc. 76, 3931 (1954). (8) Lewis, G. N.. Kasha, 11..Ibid.. 66, 2100 (1944). (9) lloodie, A I . ll.,Reid, C . , J . Chem. P h y s . 22, 252 (1954). (IO) Schoental, R., Scot, E. J. Y., J . Chem. Soc. 1949, 1683. (11) Shpol'sku, E. V.,Il'ina, -4.-i., Bsilevich, V. V., Izvcst. A k a d . A'aub S.S.S.R. Ser. F i z . 12, 519 (1948). Shpol'sku, Il'ina, Klimova, D o k l ady A k a d . S.S.S.R. 8 7 , (12) 935 (1952). RECEIVED f o r review December 5 , 1955. A c c e p t e d Ar1,oust 8, 1956.
