Photolysis of hexachlorocyclopentadiene in water

ECOTOXICOLOGY

AND

ENVIRONMENTAL

Photolysis ROBERT Research

SAFETY

6, 347-357 (1982)

of Hexachlorocyclopentadiene G. BUTZ, CHINC

and Development

C. Yu, AND YOUSEF H. ATALLAH

Department, Velsicol Chemical Chicago, Illinois 6061 I Received

in Water

January

Corporation,

341 E. Ohio

Street,

6, 1982

14C-Hexachlorocyclopentadiene (hex) (CC1 6) was photolyzed rapidly when dissolved in water and irradiated with a mercury-vapor light source. The photolytic half-life of hex was less than 1.03 min. Pentachlorocyclopentenone was tentatively identified as the primary photolyslis product of hex. After 10 min of irradiation 44% of hex radiocarbon equivalents were converted to water-soluble photoproducts. Neither mirex nor Kepone were detected as photoproducts.

Hexachlorocyclopentadiene (hex) ( C5C16) is an intermediate in the manufacture of cyclodiene insecticides, the acaricide dienochlor (see Table 1 ), and several flame retardants for resins and plastics. It has been listed as a priority pollutant by the U.S. Environmental Protection Agency (EPA). Hex is very reactive, undergoing substitution and addition reactions to form acids, esters, ketones, quinones, nitriles, and other halogenated hydrocarbons. This reactivity is due to the diene of hex, which reacts with olefins and polynuclear aromatic hydrocarbons in the Diels-Alder reaction.. Photolysis has been suggested as the major process responsible for hex degradation in such ecosystems as ponds and eutrophic lakes. Estimates of photolytic transformation were 87 and 97% of the load applied to these two types of ecosystems, respectively (Zepp et al., 1979). At a concentration of 2.2 ppm in water, hex was shown to be rapidly converted to water-soluble products when irradiated with light (X greater than 290 nm) (Yu and Atallah, 1977). The photomineralization of hex adsorbed to silica gel and irradiated (X greater than 290 nm) in an oxygen atmosphere has also been demonstrated (Korte, 1978). In aqueous systems irradiated with sunlight, hex was observed to be extremely photoreactive (half-lives less than 10 min) (Zepp et al., 1979). Zepp and his co-workers also showed that, in addition to direct photolysis, photosensitized reactions occur in natural water systems. These authors suggested that tetrachlorocyclopentadienone (TCPD) (C5C140) is a primary product of hex photolysis, although they did not isolate this compound. It was postulated that TCPD dimerizes to form a diketone (C,,C1,02; Table 1, VII) that decomposes with the release of phosgene to form a stable hexachloroindenone (C#&O) (Dietsche, 1966). More recently, Kahn et al. (1980a and b) reported a “mirex-type compound” and Kepone hydrate as possible hex photolysis products. Kepone and mirex are extremely persistent compounds. One of the objectives of this study was to determine if either of these compounds was a photolysis product of hex. The major objectives, however, were to determine the rate of hex photolysis in water and to identify the primary photoproduct( 347

0147-6513/82/040347-l

1$02.00/O

Copyright 0 1902 by Academtc Press. Inc. All rights of reproductnn in any form reserved

348

BUTZ. YU, AND ATALLAH

CHEMICALS Technical-grade hex, Lot B-8A (98.7% by GC), was used to make an aqueous solution. Descriptions of the analytical standard for hex and other compounds of interest are shown in Table 1. Only glass-distilled-grade solvents were used. Aquasol (New England Nuclear, Boston, Mass.) was used for all liquid scintillation counting. The “C-hexachlorocyclopentadiene (uniform label) was synthesized by Pathfinder Laboratories, Inc., St. Louis, Missouri (Lot No. 79-273) and had a specific activity of 22.5 mCi/mmol. Its radiochemical purity was greater than 95%. The 14C-hex was dissolved in hexane at a concentration of 20 &i/ml.

TABLE STANDARDS

Compound I. Hex (hexachlorocyclopentadiene) II. 2,3,4,4,5Pentachloro2-cyclopentenone III. Hexachloroindenone

USED

FOR ANALYSIS

Empirical formula

95.9% (GC)

Velsicol

99.7% (GO

Velsicol

99.3%

Velsicol Ref. Std. RS-HK28-112177

c#&o

(GC)

[dodecachlo-

98.8% (GC)

94.3% (HPLC)

Ref. Std.

RS-HI-53080

Velsicol

Ref. Std.

RS-HK88-121577

Velsicol Ref. Std. RA 15669

Aldrich Chemical No. S34237-8

G&1’0

c&1’*

Ref. Std.

RS-PC1542180

ICN Pharmaceuticals No. 19209

GCl402

VII. Octachloro-3,4,7,7tetrahydro-4,7methanoindene1,8dione (hex ketone dimer)

rooctahydro-1,3,4-

Source

CSHCl,O

C&O

IX. Mirex

Purity (method)

Velsicol Ref. Std. RS-HX-5 1278

V. Hexachloro-3cyclopentenone

Dienochlor [ Bis (pentachlorocyclopentadienyl)]

PRODUCTS

99.8% (GC)

C&O

VIII.

OF HEX

cd&

IV. Hexachloro-2cyclopentenone

VI. Tetrachlorocyclopentene-1,3-dione

1

100% (GC)

Hooker Ref. Std. RA 13949

metheno-2H-

cyclobuta (cd) pentalene] X. Kepone [ decachlorooctahydro-1,3,4metheno-2H-cyclobuta (cd) pentalen2-one]

cloclloo

90.1%

Allied Chem. Corp. technical grade

HEX

PHOTOLYSIS

MATERIALS

349

IN WATER

AND

METHODS

Apparatus. A l-liter capacity photoreactor with stopcock (No. 7844-12, Ace Glass, Inc., Vineland, N.J.) was equipped with a borosilicate glass immersion well (No. 7857-10, Ace Glass, Inc.) and was used with a 450-W medium-pressure mercury-vapor lamp (No. 7825-34, .Ace Glass, Inc.). The energy output of this lamp is approximately 40 to 48% ultraviolet, 40 to 43% visible, and the remainder infrared radiation. The radiometric power (irradiance) was measured by means of an autoranging radiometer/photometer (Model 550, EG & G Electra-optics, Salem, Mass.) equipped with a silicon multiprobe sensitive to ultraviolet, visible, and infrared radiation. The radiometric power at the center of the irradiated layer in the photoreactor was 6.4 X lo-* W/cm*. FRN 8195 LFtRGST 4: LAST 4:

SPECTRUN 301.2.100.0 334.2,

25.0

126 303.2, 336.2,

63.5 57.7

RETENTION 166.1, 31.5 338.2, 53.8

TINE

-I

9.2 299.2, 340.1.

PAGE

1

57.7 25.0 Y

=

1.00

-r00 a0 60. 40.. 20..

00 I

60 40

FIG. mixture 204°C.

1. GCMS fragmentation pattern of a hex photoproduct extracted from the aqueous reaction by 2% methanol in toluene, 100 to 600 AMU. The retention time of 9.2 min corresponds to

350

BUTZ,

FRN 8243 LARGST 4: Last 4:

YU,

SPECTRUPI

301.1,100.0 341.1,

2.2

AND

ATALLAH

75 303.1, 342.1,

63.4 5.3

RETENTION TImE 3.2 336.1, 62.0 299.1, 60.7 343.1, .5 344.0. .5 Pf+GEl V1.00

30. 30. 30.. 10.. !0. 0.

FIG. AMU.

2. Mass

fragmentation

pattern

of hexachloroindenone

obtained

by DIP

at 200°C.

40 to 400

Treatment and sampling. The treatment solution was prepared by adding 1.27 ~1 of the technical-grade hex to 1 liter of distilled water. An additional 1.0 ml (20 &i) of the 14C-hex in hexane was added. The total hex concentration in this solution was calculated to be 2.2 pg/ml. A loo-ml aliquot of the solution was taken before irradiation for use as a dark control. The remaining 900 ml was irradiated and a 400-ml sample was removed after 5 min as was another 400-ml sample at 10 min. The photoreactor was sealed during illumination to prevent loss of hex vapor or gaseous photoproducts. In a second experiment a single 5-hr sample was collected to determine if mirex and/or Kepone were photoproducts of hex after extended irradiation. Extraction of samples. Samples were immediately extracted for 16 hr on a roller

HEX PHOTOLYSIS

351

IN WATER

mill (Norton, Akron, Ohio) with 3 ml of 2% methanol in toluene (Borsetti and Roach, 1978) to recover the remaining hex, mirex, Kepone, or other photoproducts that may have been formed. The toluene layer was removed by aspiration and the extraction was repeated. The aqueous fraction of the samples were then extracted twice with 25 ml of ethyl acetate. Aliquots of each fraction (toluene, ethyl acetate, and aqueous) were radioassayed in 13 ml of Aquasol using a Searle Mark III liquid scintillation counter. All counts were corrected for quenching using an external standard pulse method. Counting efficiency was determined by an on-line computation program. Background counts were substrated from all samples. The aqueous fractions from the 5- and lo-min sampleswere then lyophilized in a Virtis Model lo-100 Uni-Trap lyophilizer (Gardiner, N.Y.). Identification of photoproducts. Hex photolysis products were purified and tentatively id.entified by one- or two-dimensional thin-layer chromatography (TLC) on silica gel plates (0.25 mm) with UV,,, indicator (Brinkmann Instruments, Inc., Westbury, N.Y.). Many of the standards shown in Table 1 were used to determine the presence or absence of a particular compound in the samples. The lyophilized aqueous samples were taken up in methanol for TLC analysis. The volume ratios for the solvent systems employed were: cyclohexane:chloroform, 4:l; methanol:diethylamine, 100: 1; methanol:toluene:diethylamine, 40:60: 1; and methanol:toluene:diethylamine, 10:90: 1. Autoradiographs were made of the TLC plates. Kodak Blue Brand X-ray film (Kodak, Rochester, N.Y.) was used and processed manually. Radiocarbon located by autoradiography was scraped from the TLC plates, added to 2 ml of methanol in a scintillation vial, extracted by shaking for 2 hr, and radioassayed after adding 12 ml of Aquasol. Samples were assayed for hex, Kepone, mirex, and unknown photoproducts by GC-mass spectroscopy on a Hewlett-Packard 5982A/5934A GC-MS data system (Palo Alto, Calif.). The electron impact (EI) mode was operated at 70 eV for all mass spec’troscopy work reported. GC-MS analysis were conducted using a 2 m X 2 mm-i.d. column of 3% OV101 on 80/100-mesh Gas Chrom Q. The column was operated isothermally at 230°C with a flow rate of 35 ml/min helium for assay of hex, Kepone, and mirex. For the analysis of hex photoproducts, the column was temperature programmed

TABLE

2

PARTITIOININCOFRADIOCARBON AFTER IRRADIATIONOF ?-HEX AQUEOUSSOLUTION FOR 0, ~,OR 10 min FOLLOWED BY SEQUENTIAL EXTRACTION

Percentageof 14C Fraction

0

5

IO

1. ExtracteNdby 2% methanol in toluene 2. ExtracteNdby ethyl acetate 3. Water soluble

94 3 3

20 36 44

24 32 44

100

100

100

Total

352

BUTZ,

(see Figs. l-7). Mass spectra in Table 1 were also obtained

YU,

AND

ATALLAH

for some samples and most of the standards by direct insertion probe (DIP).

RESULTS

AND

listed

DISCUSSION

Hex was not detected in samples irradiated 10 min or 5 hr (limit of detection = 0.13%). This suggests a photolytic half-life of less than 1.03 min for hex, assuming first-order reaction kinetics. Neither mirex nor Kepone were detected in any samples (limit of detection 0.06% for mirex or Kepone). The only suggestion of formation of higher-molecular-weight compounds was the isolation of a compound that was identified as hexachloroindenone (C9C160, m/e 334, Table 1, III) from the toluene

FRN LfiRGST LnST

8194 4: 4:

337.1,100.0

SPECTRUII

137.1.

340.1,

7.0

341.1,

60

92.3

RETENTION 83.5 274.1,

39.3

342.2,

TImE

3.5

339.1,

5.5

343.2, PACE1

76.1 8.1

v-

100. 80. 60. 40.. 20..

60. 40.,

FIG. 3. GC-MS fragmentation pattern of hex photoproduct The compound was tentatively assigned the formula C9HC170, time of 5.5 min corresponds to 174°C.

isolated from the ethyl acetate extract. m/e 370, 100 to 600 AMU. The retention

1

HEX

FRN 8194 LCIRGST 4: LIlST 4::

PHOTOLYSIS

SPECTRUR 218.i.i00.0 375.1,

76 154.1,

as.1

IN

376.1.

91.8

3.8

353

WATER

RETENTION 155.1, 89.4 9.9

TIME

6.4 Z16.1.

377.1,

74.4

379.1, PACE1

a.0 V-

1.88

00.

80. 60. 40..

0

ab

4ib

60

80

100

120

148

16C

00

40

30 i

FIG. 4. GC-MS fragmentation pattern of hex photoproduct isolated from the ethyl acetate extract. 100 to 480 AMU. The compound was tentatively assigned the formula C,CIRO, m/e 404. The retention time of 6.4 min corresponds to 181.2”C.

extract ( LO-min sample). This was the only chlorinated compound found in this extract. The GC-MS fragmentation pattern of this product and its authentic standard are shown in Figs. 1 and 2, respectively. A minor pathway of hex photolysis is the formation of higher-molecular-weight ketones (such as hexachloroindenone). If this pathway were major, the accumulation of such ketones would be expected because they are more stable than the hexachloro (IV and V), pentachloro (II), or tetrachloro (VI) ketones of hex. Table 2 shows the partitioning characteristics of 14C-hex photoproducts between 2% methanol in toluene, ethyl acetate, and water. Hex is rapidly converted to ethyl acetateextractable (36%) and water-soluble (44%) compounds and there is little difference between the 5- and lo-min samples. Furthermore, these findings are in agreement

354

BUTZ,

FRN LfiRGST LCIST

8448 4:

YU,

SPECTRLU’l

139

166.0.100.0 340.6.

4:

AND

12.3

119.0,

98.8

341.1.

1.1

ATALLAH RETENTION 301.1. 84.0 342.0.

TImE

8.5 118.0.

3.8 PACE1 344.1, v-

86.9 i:ee

100. 80.. 60..

20

40

60

88

100

120

140

16

00.

80 60 i

348

360

FIG. 5. GC-MS fragmentation of 8.5 min corresponds to 196”C,

380

400

420

448

pattern of 2,3,4,4,5-pentachloro-2-cyclopentenone. 100 to 480 AMU. Compare to Figs. 1 and 2.

460

The retention

4ac

time

with an earlier study where 49% of the i4C was converted to water-soluble products after 30 min of irradiation (Yu and Atallah, 1977). This rapid photolysis to watersoluble compounds supports the contention that the dimerization of hex or hex ketone (if it occurs) is not a major pathway of aqueous hex photolysis. Considerable 14C was found in the ethyl acetate fraction at 5 and 10 min (Table 2). GC-MS analysis of the extract (IO-min sample) revealed small amounts of hexachloroindenone (CgC160, m/e 334, III) and two other compounds with molecular ions of m/e 370 and m/e 404 (Figs. 3 and 4) that were tentatively assigned the formulas C9HC1,0 and CgC180. Because hexachloroindenone and the hex ketone dimer (CloC1802~ 4H20, VII) preferentially extracted from aqueous solution

HEX 8444 4:

FRN

LAROST LAST

219.0.100.0

4:

SPECTRurl 5.1

256.0.

PHOTOLYSIS

217.8, m.1,

15

355

IN WATER

80.3 .4

FcrENT1cYdt1rE 191.0, 74.9 258.0, 2.1

.7

109.0, 260.8. PerYE

Y-

58.3 -3 1.00

-I00 80 68 40 20 0 II

20

40

se

08

100

la

140

166

Cm f

40

FIG. 6. Mass fragmentation pattern of 2,3,4,4,5-pentachloro-2-cyclopentenone 35”C, 40 to 400 AMU (40 to 320 AMU shown).

obtained

by DIP

at

into 2% methanol in toluene (versus subsequent ethyl acetate extraction), it was suspected that these two compounds were artifacts of the GC-MS analysis. They appeared to be less polar than expected for an ethyl acetate-extractable compound. They would be expected to partition into the initial extractant, 2% methanol in toluene. In an effort of determine if these two compounds were GC artifacts of any of the standards, GC-MS and DIP-MS analyses were conducted with all of the hex ketones and a diketone of hex available as authentic standards (Table 1, Stds. II, IV, V, and VI). GC-M:S analysis of authentic standard of 2,3,4,4,5-pentachloro-2-cyclopentenone (Table I, II) revealed that this compound was converted in the GC-MS to hexachloroindenone (Fig. 5). DIP-MS analysis of compound II at 35°C showed that this compound remained intact (Fig. 6). However, at 42”C, DIP-MS analysis of compound II showed that it dimerized and then decomposed to C&l80 (Fig. 7). This supports the contention that the hexachloroindenone, C9HC1,0, and C&l80 compounds observed here in the ethyl acetate extract are GC artifacts and are derived from 2,3,4,4,5-pentachloro-2-cyclopentenone. It is also possible that other pentachlorocyclopentenone isomers (not available as authentic standards) were the compounds in the ethyl acetate extract that gave rise to the hexachloroindenone, C,HCl,O, and C&l80 compounds believed to be GC artifacts. When a saturated aqueous solution of 2,3,4,4,5-pentachloro-2-cyclopentenone (II) was extracted sequentially with 2% methanol in toluene and then ethyl acetate,

356

BUTZ,

FRN

8444

YU,

SPECTRUm

ATALLAH

32

69.1, 374.0,

a4.i.ise.~~

W3.0,

AND

2.8

65.2 .3

RETENTION 77.1, 55.3 375.0, 1.6

TIPlE Piwz

1.4 49.1, 46.7 377.0, .5 1 Y 1.04

G0i 40

t

I

0. 20

40

60

80

100

120

140

16

80.. 60.. 40

FIG. 7. Mass fragmentation 42’C, 40 to 480 AMU.

pattern

of 2,3,4,4,5-pentachloro-2-cyclopentenone

obtained

by DIP

at

most of the chemical was found in the ethyl acetate. Aqueous II was converted rapidly to hexachloroindenone in darkness at 25°C. Therefore, it is possible that the hexachloroindenone found in the toluene and ethyl acetate extracts was a product of the spontaneous aqueous dimerization of pentachlorocyclopentenone and not a photolysis product. A proposed scheme for the formation of hex photoproducts, hydrolysis products, and GC artifacts is shown in Fig. 8. The structures of C,HCl,O and C&&O are also proposed as XI and XII, respectively (Fig. 8). It is concluded that pentachlorocyclopentenone may be the primary photoproduct of hex in water. In addition, dimerization products similar to hexachloroindenone may represent a minor route of degradation. Hex in an aqueous solution is not photolyzed to mirex or Kepone.

HEX

PHOTOLYSIS

IN

rCl

Cl

Cl u Cl

Cl

1

Cl xv, -

Cl

0

+c

H Cl

Cl 0 Cl

-cl +OH

357

WATER

Water-soluble Photopmd”cts

-

Cl

I Hydrol”Dl* /’

/’ Cl

,’

/

/’ -2tic1 -COCI,

’

Cl

Cl )

cl

Cl

Cl 07 Cl

0

Cl

0

Cl

XII

III -b

M.,0r

-----

PAnor

FIG. 8. Proposed

pathway

of aqueous

0 XI

hex photolysis.

The major pathway of aqueous hex photolysis is the formation of water-soluble compounds. The photolytic half-life of aqueous hex is less than 1.03 min. REFERENCES BORSETTI, A. P., AND ROACH, J. A. (1978). Identification of Kepone alteration products in soil and mullet. I3ull. Environ. Conlam. Toxicol. 20, 241-247. DIETSCHE, W. H. (I 966). Diels-Alder reakionen mit tetrachlorocyclopentadienon. Tetrahedron Leff. (2). 201-204. KHAN, M. A. Q., FEROZ, M., PODOWSKI, A. A., AND MARTIN, L. T. (1980a). Ecological and health effects o:f the photolysis products of chlorinated hydrocarbon pesticides. In D.vnamics, Exposure and Hazard Assessment of Toxic Chemicals (R. Haque, Ed.), p. 409. Ann Arbor Science Pub.. Ann Arbor, hdich. KHAN, M. A. Q.. SUDERSHAN, P., FEROZ, M., PODOWSI, A. A., AND SHACKLEFORD. M. (1980b). Comparative metabolism of hexachlorocyclopentadiene. cyclodienes, and their photoisomers in fish and mammals. In 2nd Chemical Congress of rhe North American Conrinent, Abstracrs of Papers, Part I. ENVR. 176. KORTE, F. (1978). Photomineralization of Hexachlorocyclopentadiene and Ecotoxicological Profile Analysis of Hexachlorocyclopentadiene (HCCP). Report to Velsicol Chemical Corporation. NEWCOMER, J. S., AND MCBEE, E. T. (1949). The chemical behavior of hexachlorocyclopentadiene. I. Transformation to octachloro-3a,4,7,7a-tetrahydro-4,7-methanindene-l,8-dione. J. Amer. Chem. Sot. 71, 946-951. Yu, C. C., .&ND ATALLAH, Y. H. (1977). Photolysis of Hexachloroeyclopentadiene. Project No. 482428, Report No. 4. Velsicol Chemical Corporation. ZEPP, R. G., WOLFE, N. L., BAUGHAM, G. L., SCHLOTZHAUER, P. F., AND MACALLISTER, J. N. (1979). Dynamics of processes influencing the behavior of hexachlorocyclopentadiene in the aquatic environment. In 178th ACS National Meeting. Absrracts of Papers. Part I. ENVR. 042.