in converter No. 1. The concentration of lead salts in the washcoat is also less than in converter No. 1. Even with this moderate level of contamination, the hydrocarbon conversion efficiency was reduced from 100 to 54%. Again, the outlet region had few contaminant crystals on the surface and a much lower concentration in the washcoat.
Discussion Contaminants are thought to reduce catalytic activity by chemically reacting with the active elements or by physically introducing a barrier between them and the gas phase. The latter mechanism is evident i n the results of this examination. Lead salts [PbS04 and Pb3(P04)2] nucleate from the vapor phase as small crystals on the washcoat surface. These crystals grow and may eventually coalesce to form a continuous solid layer that restricts gas transport into the washcoat. Under certain conditions, crystals nucleate on one another to form treelike structures. It is likely from their fragile appearance, that these deposits occasionally break off and go out the exhaust as
particulates, but we have no evidence that this occurs to any significant degree. Deposition of these salts within the washcoat micropores also occurs. In heavily contaminated catalysts, the washcoat pore structure appears to be completely plugged with lead salts. Zinc and iron were not observed to penetrate the washcoat, presumably because they are deposited as particulates and do not have a significant effect on catalytic activity. Acknowledgments The authors wish to thank M. Shelef and J . T. Kummer for many helpful comments and also R. C. McCune for providing the transmission electron micrograph. Mrs. A. G. Piken made the catalyst efficiency measurements and correlated them with lead concentration. R. A. Armstrong and M. A. Short provided the X-ray fluorescence data. Receiued for review June 3, 1974. Accepted O c t . 18, 1974
Two Pyrene Derivatives of Widespread Environmental Distribution: Cyclopenta (cd) pyrene and Acepyrene Lawrence Wallcave,,* Donald L. Nagel, James W. Smith, and Ralph
D. Waniska
Eppley Institute for Research in Cancer, University of Nebraska Medical Center, Omaha, Neb. 68105
An orange polycyclic aromatic hydrocarbon with reported tumorigenic properties, isolated from carbon black and other soots by several previous investigators, was identified as cyclopenta(cd)pyrene. This compound is the first known cycloalkenyl pyrene derivative. It was characterized by elemental analysis, proton magnetic resonance, mass spectroscopy and uv-vis spectroscopy. A benzene extract of the carbon black used for its isolation contained 60-fold more cyclopenta(cd)pyrene than benzo(a)pyrene. Hydrogenation of cyclopenta(cd)pyrene yielded acepyrene (3,4-dihydrocyclopenta(cd)pyrene).The latter hydrocarbon is present in relatively abundant concentrations in coal tar pitch. The mass spectrum, proton magnetic resonance spectrum, and quantitative uv spectrum of acepyrene are reported.
Twenty-three years ago Falk and Steiner ( I ) reported the isolation of a “yellow crystalline” substance from benzene extracts of certain carbon blacks but did not identify it. The same substance was later found in gasoline engine exhaust particulates and in incinerator soots ( 2 ) . A substance described as an “orange compound (pyrene derivative?),’’ whose uv wavelength maxima and chromatographic properties closely matched those of the “yellow” compound, was reported as being present in gasoline and diesel engine exhausts and in general atmospheric soot (3). Most recently the compound of Falk and Steiner was isolated from carbon black and from petrochemical inplant atmospheres by Neal and Trieff ( 4 ) who also concluded it was a pyrene derivative. They found that it pro-
duced fibrosarcomas at the site of injection into CFW mice. Although carbon black itself appears to be physiologically inactive in a variety of animal species, benzene extracts of some types are carcinogenic by skin painting or subcutaneous injection (5, 6 ) . Benzo(a)pyrene has been the only known carcinogen identified in such extracts. We isolated about 100 mg of the same orange compound from 2 kg of a selected carbon black having a relatively high proportion of extractable polycyclic aromatic compounds, and identified it as cyclopenta(cd)pyrene (Figure l a ) . It was approximately 60-fold more abundant than benzo(a)pyrene in this extract. Table I lists the polycyclic
C) Figure 1.
Polycyclic aromatic hydrocarbon structures
(a) Cyclopenta(cd)pyrene, (b) acepyrene, ( c ) benzo(ghi)fluoranthene, ( d ) cyclopenta(cd)fluoranthene
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aromatic hydrocarbon constituents identified in this sample. Of seven other carbon blacks examined, cyclopenta(cd)pyrene was not detected in three and ranged from about 1-65 pg/g in the others. Cyclopenta( cd)pyrene is the first known cycloalkenylpyrene derivative and its reported tumorigenic properties and wide environmental distribution make the finding of more than routine interest. Since the uv spectrum of cyclopenta(cd)pyrene (Figure 2) more closely resembled that of benzo(ghi)fluoranthene (7) than it did a pyrene derivative, we considered that the unknown might be cyclopenta( cd)fluoranthene (Figure Id). However, the proton magnetic resonance (pmr) spectrum was compatible only with the pyrene structure. The mass spectrum of cyclopenta(cd)pyrene established its molecular weight as 226 but was not clearly distinguishable from that of the isomeric benzo(ghi)fluoranthene. Hydrogenation of cyclopenta( cd)pyrene yielded a 3,4dihydro- derivative, ClsHlz (Figure Ib). The dihydro compound was previously tentatively identified by mass
Table 1. Polycyclic Aromatic Hydrocarbons in Selected Carbon Black Compound
Concn, P g l g
Acenaphthylene Pyrene Fluoranthene Benzo(ghi)fluoranthene Cyclopenta(cd)pyrene Benzo(a)pyrene Benzo(e)pyrene Benzo(ghi)perylene Antha n t hrene I n den o( 1,2,3-cd)pyre ne Coronene
5.9 160 52 24 97 1.7 2.3 35 8.5 4.0 73
7
6
II I1
!!
5
* 0 X
g 4
2
/5
B
% 3
a
LL
50 5
2
1
WAVELENGTH (om)
Figure 2. Uv-vis spectra in
hexane
Solid line: cyclopenta(cd)pyrene, maxima at 386, 374, 367, 354, 339, 310, 287, 239, and 224 nm. Broken line: acepyrene, maxima at 378, 370, 357, 344, 340, 328, 314, 277, 266, 244, and 234 nm. Spectra were determined on a Cary 14 spectrophotometer
144
Environmental Science & Technology
spectroscopy as a constituent of coal tar pitch and called acepyrene (8). (Through an error in nomenclature, acepyrene was referred to as cyclopenta(cd)pyrene in that report rather than by its correct IUPAC name of 3,4-dihydrocyclopenta(cd)pyrene.) Its presence in coal tar pitch was confirmed by comparison with acepyrene produced by the hydrogenation of cyclopenta(cd)pyrene. The pitch (type RT-12) was analyzed by methods previously described (9) and contained about 0.2% of acepyrene, a concentration nearly equal to that of the methylpyrenes. Since acepyrene isolated from pitch was not completely separated from small amounts of methylbenzofluorenes, the pure compound for characterization was obtained by the hydrogenation route. A synthesis of acepyrene was recently reported but no data other than melting point and elemental analysis were presented. It inhibited zoxazolamine hydroxylase formation in rats and was being tested for carcinogenic activity in mice ( I O ) . Acepyrene is apparently identical to the unidentified pyrene derivative isolated from ethane and ethylene flame soots by Chakraborty and Long (11) as it has a nearly identical uv spectrum (Figure 2) and a similar retention time on glc. Therefore, it is quite likely that acepyrene, like cyclopenta(cd)pyrene, has a wide environmental distribution. Crittenden and Long (12) have reported on the probable presence of cyclopentacenaphthylenes (such as pyracylene) in flame soots. Additional cyclopenta-substituted polycyclic hydrocarbons will doubtless be discovered as more detailed investigations of the alkylaromatic components of tars and soots are pursued. Experimental Extractions a n d Chromatography. Material for analysis was obtained by extracting 10 grams of carbon black with benzene for 20 hr in a Soxhlet apparatus. One tenth of the extract residue was chromatographed on a 0.25-mm layer of alumina (20 X 20 cm, MN “Alox,” Brinkmann Instruments, Inc.). The chromatogram was developed with 1:19 (v/v) benzene:hexane and the development repeated three times. Cyclopenta(cd)pyrene, a nonfluorescent band (dark absorption), occupies a position between the pyrene and benzo(a)pyrene bands. Concentrations of the known aromatic constituents were obtained by photometric estimations using baseline techniques. Rechromatography of the cyclopenta(cd)pyrene on tlc separated benzo(ghi)fluoranthene as a fluorescent area a t the leading edge of the cyclopenta(cd)pyrene band. Crystalline cyclopenta(cd)pyrene for characterization was obtained by extracting 10 x 200-gram portions of carbon black with benzene. The residue from the combined extracts was chromatographed on 240 grams of slightly deactivated alumina (Fisher A-540 adjusted to a 10% water content) in a 32 X 460 mm column. As mentioned by Neal and Trieff ( 4 ) , the cyclopenta(cd)pyrene forms a nonfluorescent, pale orange-yellow zone. The cyclopenta(cd)pyrene was eluted with 1:9 benzene:hexane and recrystallized from hexane. Twenty-five milligrams were rechromatographed on a 1.0-mm layer of alumina (MN “Alox”) using repeated development with 1:19 benzene:hexane. Characterization of Cyclopenta(cd)pyrene. Crystallization of the tlc-purified compound from ethanol gave orange-red plates, m.p. 173°C (Neal and Trieff, 167°C). (Anal. Calcd for C18H10: C, 95.55; H, 4.45. Found: C, 95.58; H, 4.50) (Micro-Tech Laboratories, Inc., Skokie, I11.) Mass spectra were obtained with an AEI MS-9 spectrometer (Table 11). A base peak a t m/e 226 corresponded
Table II Re1 intensity,
Re1 intensity, w e
%
Mle
%
Re1 intensity, Mle
%
A. Mass Spectrum of Cyclopenta(cd)pyrenen 228 227 226 225 224 223 222 221 200 199
3.0 19.9 100.0 11.9 16.9 4.2 3.3 0.6 0.9 0.7
198 174 114 113.5 113 112.5 112 111.5 111 100
1.3 0.6 0.5 5.3 19.1 5.0 12.3 2.9 2.2 2.0
99.5 99 98 87 86 75.3 75 74
0.8 2.1 0.8 1.0 0.6 0.5 0.7 0.8
B. Mass Spectrum of Acepyrenea
230 229 228 227 226 225 224 223 222 201 200 199
1.6 17.9 100.0 51.4 45.0 9.9 10.9 2.5 1.8 0.7 1.9 ^
^
U.Y
198 174 150 114.5 114 113.5 113 112.5 112 111.5 111
.^.lU1.3
1.1 0.7 0.5 1.9 10.8 10.6 17.6 5.9 10.4 2.1 1.3 u. I ^
101 100.5 100 99.5 99 98 88 87 75.3 75 74
3.6 1.0 4.0 1.0 1.5 0.6 0.8 1.2 0.6 0.8 0.6
?
a Relative intensities of 0.5 or greater for all M / e >_ 40. Direct probe inlet; ion source temperature, 200 C; electron energy, 70 eV.
drogenated on a small scale using in situ generation of hydrogen. One milliliter of a 0.5% ethanolic solution of NaBH4 was introduced by means of a hypodermic syringe into a stirred mixture of 35 mg of cyclopenta(cd)pyrene, 0.5 ml of concd HC1, 7 mg of 10% palladium on charcoal and 10 ml of ethanol in a stoppered flask. Uv spectrometry indicated a nearly quantitative conversion after 30 min. After partition chromatography on Whatman 3MM paper using a DMF-isooctane system (14) and crystallization from benzene-ethanol, 12 mg of acepyrene were obtained, m.p. 133-4°C (Buu-Hoi et al., 132°C). (Anal. Calcd for C&12: C, 94.70; H, 5.30. Found: C, 94.76; H, 5.29.) The mass spectrum of acepyrene (Table 11) was appreciably different from that of a purely aromatic ClsHlz isomer such as chrysene or benzanthracene. The P-1 and P-2 peaks presumably corresponding to the loss of cyclopentyl hydrogens were very intense. The great stability of the resulting cyclopenta(cd)pyrene structure produces a doubly charged ion at m/e 113 that is even more intense than the doubly charged parent ion at m/e 114. The pmr spectrum of acepyrene consisted of a broad singlet at 6 3.62 integrating to four protons (cyclopentyl) and a complex multiplet from 6 7.60-8.10 integrating to eight protons (aromatic). The uv spectrum is that of an alkyl substituted pyrene (Figure 2). Acknowledgment We thank R. Roth and E. Cavalieri for helpful discussions on pmr interpretation and P. Issenberg for advice on mass spectrometry. Literature Cited (1) Falk. H. L:. Steiner. P . E.. Cancer Res.. 12.30-8 (1952).
to the molecular ion. The peak at 113 due to the doubly charged molecular ion was very intense. Since these characteristics are also shown by the purely aromatic Cl&o isomer, benzo(ghi)fluoranthene, the two compounds are not readily distinguishable by mass spectrometry. Pmr spectra were determined on a Varian HA-100 spectrometer as carbon tetrachloride solutions using tetramethylsilane as an internal reference. The isolated orange compound exhibited an AB quartet centered at 6 7.16, J = 5.3 Hz, integrating to 2 protons (cyclopentyl) and a complex multiplet from 6 7.75 to 8.30 integrating to eight protons (aromatic). Cyclopenta( cd)pyrene is expected to exhibit an AB pattern for the CS and Cq (cyclopentenyl) protons, whereas cyclopenta( cd)fluoranthene would have a plane of symmetry making these protons constitutionally equivalent and hence isochronous. The chemical shift shown by the cyclopentenyl protons is close to that reported for the corresponding protons in acenaphthylene [6 7.15 ( 1 3 ) ] . Hydrogenation of Cyclopenta(cd)pyrene and Characterization of Acepyrene. Cyclopenta(cd)pyrene was hy-
(2) Kotin, P., Falk, H . L., Thomas, M., Arch. Industr. Hyg , 9, 164-77 (1954). (3) Lyons. M. J.. Nat. Cancer Inst. Monoerauh No. 9. DD 193-9. 1962. Cf. compound 11,Table 1. (4) Neal, J., Trieff, N. M., Health Lab Sci , 9,32-8 (1972). (5) Steiner, P . E.. Cancer Res., 14, 103-10 (1954). (6) Nau, C. A., Neal, J., Stembridge, V. A,, Arch Enuiron Health, 4, 415-31 (1962). ( 7 ) Clar. E., “Polycyclic Hydrocarbons,” Vol. 2, .D 336,. Academic Press, London, i964. (8) Wallcave, L., Enuiron. Sei. Technol. 3,948 (1969). (9) Wallcave, L., Garcia, H., Feldman, R., Lijinsky, W., Shubik, P., Toxicol. Appl. Pharmacol. 18,41-52 (1971). (10) Buu-Hoi, N. P., Jacquignon, R., Hoeffinger, J . - P . , Jutz, C., Bull. SOC.C h k . , 1972,2514-16 (1972). (11) Chakraborty, B. B., Long, R., Enuiron. Sei. Technol., 1, 828 ‘ (1967). (12) Crittenden, B. D., Long, R., ibid., 7,742-4 (1973). (13) Jackman, L . M., Sternhell, S., “Applications of Kuclear Magnetic Resonance Spectroscopy in Organic Chemistry,” 2nd ed., p 188, Pergamon Press, London, 1969. (14) Lijinsky, W., Anal. Chem., 32,684-7 (1960). I
.
I .
Received for revieu’ June 21, 1974. Accepted October 24, 1974. Work supported in part under contract PH-43-NCI-E-68-959 with the National Institutes of Health.
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