O 9 naMa be te. Formation of polychlorinated dibenzodioxins and dibenzofurans by heating chlorophenols and chlorophenates at various temperatures.
O 9 naMa be te
Formation of polychlorinated dibenzodioxins and dibenzofurans by heating chlorophenols and chlorophenates at various temperatures W. Zoller and K. Ballschmiter Abteilung Analytische Chemie, Universitgt Ulm, Oberer Eselsberg, D-7900 Ulm/Donau, Federal Republic of Germany
Bildung yon polychlorierten Dibenzodioxinen und Dibenzofuranen dutch Erhitzen von Chlorphenolen und Chlorphenolaten bei verschiedenen Temperaturen Zusammenfassung. Polychlorierte Dibenzodioxine (PCDD) und polychlorierte Dibenzofurane (PCDF) werden dutch Pyrolyse yon Chlorphenolen und Chlorphenolaten gebildet, wobei unter bestimmten Bedingungen das PCDD-Muster vollstfindig yon der Chlorsubstitution tier Ausgangsmolektile bestimmt wird. Die Pyrolyse yon Chlorphenolen bei h6heren Temperaturen ffihrt jedoch zu komplexen PCDD/ PCDF-Gemischen. Fast alle Tri- bis Heptachlordibenzodioxine und -dibenzofurane k6nnen gleichzeitig aus einer Mischung yon nur zwei Trichlorphenolen hervorgehen. In diesere Fall wird alas Substitutionsmuster der Produkte nicht mehr von dem der eingesetzten Chlorphenole beeinflul3t. Summary. Polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are formed by pyrolysis of chlorophenols and chlorophenates. Under certain conditions the PCDD pattern is completely governed by the chlorine substitution of the starting molecules. Pyrolyses of chlorophenols at elevated temperatures, however, lead to complex PCDD/PCDF mixtures. Nearly all trito heptachlorodibenzodioxin and -dibenzofuran congeners can arise simultaneously from a mixture of only two trichlorophenols. In this case the substitution pattern of the products is no longer influenced by that of the chlorophenols used.
complex mixture of PCDD takes place. Furthermore, PCDF are formed to an increasing extent. We pyrolysed different mixtures of chlorophenols and chlorophenates systematically varying the temperature. The PCDD/PCDF formed were analyzed by HRGC/MS permitting the isomer-specific determination of the compounds formed.
Experimental All chlorophenols and chlorophenates used contained at least one C1 substituent in the ortho-position. Compounds which would lead specifically to PCDD/PCDF isomers of the 2,3,7,8-class as major components were not pyrolysed out of safety reasons. 100 gg of chlorophenols or chlorophenates were sealed in a silica micro tube (5 cm, i mm i.d.) and heated to 320~176 for 3 - 1 5 h. After cooling the tube was crushed and the reaction products were extracted with 0.5 ml toluene under ultrasonication. This solution was shaken with water. The organic phase was dried and cleaned up on an alumina micro column (1 g basic alumina, Woelm, superactiv). We first eluted with 15 ml h e x a n e - 2 % methylene chloride (LC 1) and then with 15 ml h e x a n e - 50% methylene chloride (LC 2). The PCDD/PCDF fraction (LC 2) was concentrated and transferred to 0.2 ml tetradecane as solvent. This solution was used for GC/MS analysis. GC/MS system: GC/MSD (HP 5995), capillary: 50 m CP Sil 88, 0.23 mm i.d., 0.21 ~tm df, carrier gas: He, 1 - 2 ~tl splitless injection, inj. port: 260 ~C, temperature program: 190~ 5 min, 1.6~ 240~ 40 min.
Introduction
Results
Chlorophenols are produced on a scale of thousands of tons anually. It is known that technical chlorophenols contain polychlorodibenzodioxins (PCDD) and polychlorodibenzofurans (PCDF) in the ppm range. PCDD and PCDF can be formed by pyrolytic dimerization of chlorophenols or chlorophenates [1, 2]. This is the most common way for preparation of PCDD standards. Under defined conditions the pyrolytic condensation of chlorophenates is a specific reaction leading to the formation of a single or only a few PCDD isomers. The chlorine substitution pattern of these PCDD can thus be predicted. At higher temperatures ( > 400~ and if chlorophenols are used instead of chlorophenates as starting compounds, formation of a
a) Pyrolysis of chlorophenates
Offprint requests to: K. Ballschmiter
Pyrolysis of chlorophenates at 350~ (3 h) leads to well defined PCDD isomers by direct condensation or by the Smiles rearrangement [3, 4]. Figure 1 shows a chromatogram of the T4CDD from pyrolysis of 2,3,5- with 2,3,6-trichlorophenate at 350 ~C. The T4CDD isomers and the route of their formation are listed in Table 1. Under these conditions the amount of PCDF and higher chlorinated PCDD as byproducts is less than 2% of that of T4CDD, but formation of trichlorodibenzodioxins (T3CDD) may rise to 2 0 - 5 0 % . The specificity of the reaction is partly lost at higher temperatures, but the PCDD pattern obtained at 400 ~ 440~ is still influenced by the substitution pattern of the starting chlorophenates. In addition to the major cornFresenius Z Anal Chem (1986) 323:19-23 9 Springer-Verlag 1986
OriginaJ Papers ION
PYROLYSIS OF 2, 3, 5 -
+ 2, 3, 6-TRICHLOAOPHENATE
(350~
319.9 Full Scale
=
963.8
1289
3h)
T4COD
1369
1379
1279
1469
1368 1287 1268
1289
~.0 MIN
Fig. 1. HRGC (CP Sil 88)/MSD from the pyrolysis (350~ dioxin
3 h) of 2,3,5-+ 2,3,6-trichlorophenate. SIM detection of tetrachlorodibenzo-
Table 1. T4CDD isomers formed by pyrolysis of 2,3,5-+ 2,3,6trichlorophenate at 350~ Ballschmiter number of PCDD/F [5]
T4CDD isomer
Starting chlorophenate
177 180 178 172 175 181 173 171 176
1,3,6,8 1,3,7,9 1,3,6,9 1,2,6,8 1,2,7,9 1,4,6,9 1,2,6,9 1,2,6,7 1,2,8,9
2,3,5 2,3,5 2,3,5 + 2,3,6 2,3,5 + 2,3,6 2,3,542,3,6 2,3,6 2,3,6 2,3,6 2,3,6
Smiles rearangement + + + +
pounds already mentioned, further T4CDD isomers and higher chlorinated homologues as well as PCDF are found. In Fig. 2 the chromatogram of the T4CDD, P5CDD, T5CDD, T4CDF and P5CDF obtained from pyrolysis of 2,3,4- + 2,3,6-trichlorophenate at 440~ (3 h) is depicted. The 1,2,6,9-, 1,2,6,7- and 1,2,8,9-T4CDD are still the major compounds as they can be derived directly from 2,3,4and 2,3,6-trichlorophenol. The P5CDD consist mainly of 3 + 2 compounds with a 1,2,3-structure, where the ring 20
->
closure can be explained by the expulsion of H2 or two H radicals. At this temperature also a complex mixture of T4CDF and P5CDF is formed in an amount of about 20% relative to that of T4CDD and P5CDD. Higher chlorinated PCDD and PCDF are formed in less than 1% yield. The PCDF pattern does not indicate a specific steric preference for the reaction. The formation of PCDF requires basically a reactive pathway as depicted below:
~ Clx
~
+ H20 + HC1
~
C1~r Clx
Cly
This reaction scheme, however, does not explain the predominance of trichloro- and tetrachlorodibenzofurans in the reaction mixture analyzed, indicating a more complicated reaction pathway. A possible intermediate could well be an arinradical formed by the expulsion of HC1:
~ Clx
OH C1
-HC1 O/OClx
Clx
12478 P Y R O L Y S I S OF 2 , 3 , 4 PHENATE
(440~
i2467
+ 2,3,6-TRICHLORO-
3h)
]l
A
23467
TA
P5COF 13678
.1_ ~4J6 I ~367 1247
T4CDF
t369 t268 t246 t237
24~ 1467
1236 1236 1278
t678 t234
i13479
1279 1267
12396
L. 13467 12479
ION 305.9
Full
Scale = 7B.fl
2367 2347 1239
1379 1378
3467
.,J~
ION 355.9
Full
12369
Scale = 143.0 ~238fl
12467 12367 t24
1237B P5CDD 12469~ 12347 /
12478
ION 319.9
1289
Full
Scale = 583.6
138,0
139.0
1269 1234 1237 1238 1246 t249
T4CDD 1369
1267 1278 1469
JL.
0 137,0
'~.~
O
~2378
MIN
Fig. 2. HRGC (CP Sil 88)/MSD from the pyrolysis (440~ pentachlorodibenzodioxin and -dibenzofuran P Y R O L Y S I S OF 2 , 3 , 4 PHENOL ( 3 5 0 ~ 3n)
140.0
t41.0
142.0
->
3 h) of 2,3,4- + 2,3,6-trichlorophenate. SIM detection of tetrachloro- and
12467 12478
+ 2,3,6-TRICHLORO-
14878
ION 339.9 F u l l Scale = 37.1 P5CDF
234~8
2341B 23,67
12
13678 13479
1478 t3~9
z
2468 1,t67 123Q 1236
1268
g
1246 1237
~7
1278
ION 305.9
Full
Scale = 52.9 T4COF
t279 t267
2367 2347
184fi 1234
2378
]
1247
L_t
A t2~-9 I
I( I 355.9 12346
12487
Full i2889
Scale = 165.4 P5CDO
1248
12469 12478 12479 /
1289 1278
_
_
~
t
3
7
B 8621
ION 319.9 Full Scale = 240.9 T4COD
t267 t289
1369
t248 1247
1~sTe
J249
1476 1246 1279 t236
2378 J
1469
123~
~ |234, t237, 1238
Fig. 3. HRGC (CP Sil 88)/MSD from the pyrolysis (350~ pentachlorodibenzodioxin and -dibenzofuran
HIN
->
3 h) of 2,3,4- + 2,3,6-trichlorophenol. SIM detection of tetrachloro- and 21
Or g na
Papers
PYROLYSIS OF 2, 3. 4- + 3. 4.5-TRICHLOROPHENOL PATTERN OF PCOO
(4400C.
3h)
ION 423.8 Full Scale ~ 2.6 1234679 ~ J ~
H7CDO 123689 123679 124679 124689 123468.
? z
123678
ION 389.8 123789
j
z rn
.123478
12378 12476
t2479 12468
12368
12379
J 1378
%36fl
1379
12346 12389 ----112467 ---~2489
12347 '"+
t268
t279 124fl1236 1248 I t246 t278 t247 1238 t237
123467 HBCDO
ION 355.9
Full Scale : 26B.~
+c00
2367 Lt2369
ION 319.9
t369
~
Full Scale = 4~.5
Full Scale = 292.0
-J23r 1269 1267 %289
T4COO
L
J47~23~8~" 1469J L1239
ION 288,0
Full Scale = 203.3
T3CO0
~1.0~.0~.034.~.0~.0~7.+~.0~.646
~,:.~.~+~.~,.~4~.~,~.~47.~.~4~.~m.~m.~z.+~.~.a~.+m.~s7.~.~s.o M[N
PYROLYSIS OF 2, 3, 4- + 3. 4, 5-TRICHLOROPHENOL (440 o C, 3h) PATTERN OF PCOF
IO~ 407 98 Full Scale = 6 - 6 H7CDF
1234678 II 1234679 ! ~ ~
124678 ,234..tlt2367,
.+Te
f
,
123679
ION 373.B
1234799
F u l l Scale = 50.0
H6CDF
123789 12476 12378 1 3 4 713467 ~12346 123468 12368 5478 12479
4-
13678
IAI
124679
-124689
23468 12469
1367 1247 12468t347 I I~72
1%% 1267
z
123689 123469 2~|4676
IIII 12367
13466
->
.....
23478
ION 339.9 Full Scale = t00.0 P5COF
I,++ ION 305.9
F u l l Scale = 100.0
2378 2367
T4COF
263.+ 1346 1
I
1eta1 Ie36. 123e
2346
ION 270.0
Full
Scale = 244.5 T3CDF
Fig. 4 a. H R G C (CP SI188)/MSD from the pyrolysis (440 ~C, 3 h) of 2,3,4- + 3,4,5-trichlorophenol. SIM detection of trichloro- to heptachlorodibenzodioxin, b H R G C (CP Sil 88)/MSD from the pyrolysis (440 ~C, 3 h) of 2,3,4- + 3,4,5-trichlorophenol. SIM detection of trichloroto heptachlorodibenzofuran 22
Originalart eiten The T3CDD and T3CDF are also main products. This reaction formally requires the expulsion of three chlorines, which is likely to occur as a hydrodechlorination of the T4CDD and T4CDF, respectively.
it was not possible to synthesize all the PCDF isomers but a nearly complete P ( 3 - 7)CDF mixture was obtained from pyrolysis of chlorophenols at 440 ~C and 3 h reaction time. The amount of PCDF formed was comparable to that of PCDD.
b) Pyrolysisof chlorophenols Pyrolysis of chlorophenols results in strongly reduced yields of P C D D as compared to the pyrolysis of the corresponding chlorophenates (reduction by a factor of 10). At 320~ 350~ the reaction of chlorophenols leads to a P C D D pattern which is still correlated to the starting compounds and it correlates with the P C D D pattern obtained from the corresponding chlorophenates. Figure 3 shows a chromatogram of the tetra- and pentachlorodibenzodioxins and -dibenzofurans formed by pyrolysis of 2,3,4- and 2,3,6-trichlorophenol at 350 ~C. The P C D D and PCDF patterns are still quite similar to those in Fig. 2. The main compounds (1,2,6,9-, 1,2,6,7- and 1,2,8~9-T4CDD) are superimposed on a complex T4CDD/ P5CDD/T4CDF/P5CDF mixture. In addition to the similarity of the P C D D / P C D F pattern in Fig. 2 and 3, the T 4 C D D : T 4 C D F and P 5 C D D : P 5 C D F ratios are quite constant (about 5:1) as found for the chlorophenate reaction mixtures. In analogy to the chlorophenate pyrolysis, the P C D D pattern from reactions of chlorophenols turns increasingly complex at elevated temperatures (400 ~ ~C) and the formation of PCDF becomes more pronounced. The chromatogram in Fig. 4a shows the P ( 3 - 7 ) C D D pattern from the pyrolysis of 2,3,4- and 3,4,5-trichlorophenol at 440~ Although some overlapping of isomers occurs on the column used, it seems as if22 tetra-, 14 penta-, 10 hexa-, 2 hepta- and octachlorodibenzodioxin are formed, representing all the possible P C D D ( 4 - 8 ) isomers. In the T3CDD trace 12 characteristic signals are plotted but they have not yet been assigned. In Fig. 4b the complex P ( 3 - 7 ) C D F pattern from the same reaction is plotted. In contrast as in the case of P C D D
Conclusions
PCDD standards with defined isomers as major compounds are easily available by condensation of polychlorophenates at 350~ and 3 h reaction time. At these temperatures the P C D D formed do not isomerize and no chlorination by chlorine radicals can be observed. At higher temperatures a reaction of radicals leads to the formation of PCDF and some higher chlorinated dibenzodioxins as byproducts. The reactions of chlorophenols at different temperatures show a similar tendency. Pyrolyses of chlorophenols generally lead to more complex mixtures in less specific reactions but at 3 2 0 ~ 1 7 6 the P C D D product pattern is still influenced by the substitution pattern of the starting chlorophenols. At higher temperatures (440 ~C) a very complex mixture of all P ( 4 - 8 ) C D D and nearly all P ( 4 - 7 ) C D F isomers can be formed.
References
1. Buser HR (1975) J Chromatogr 114:95-108 2. Rappe C, Marklund S, Buser HR, Bosshardt HP (1978) Chemosphere 3 :269 - 281 3. Buser HR, Rappe C (1984) Anal Chem 56:442-448 4. Gray AP, Cepa SP, Cantrell JS (1975) Tetrahedron Lett 33:2873--2876 5. Ballschmiter K, Buchert H, Class T, Kr/imer W, Magg H, Munder A, Reuter U, Sch/ifer W, Swerev M, Wittlinger R, Zoller W (1985) Fresenius Z Anal Chem 320:711 --717 Received August 22, 1985
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