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A Critical Review of Aqueous Solubilities, Vapor Pressures, Henry's Law Constants, and Octanol–Water Partition Coefficients

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A Critical Review of Aqueous Solubilities, Vapor Pressures, Henry's Law Constants, and Octanol–Water Partition Coefficients A Critical Review of Aqueous Solubilities, Vapor Pressures, Henry’s Law Constants, and Octanol–Water Partition Coefficients of the Polychlorinated Biphenyls Cite as: Journal of Physical and Chemical Reference Data 15, 911 (1986); https://doi.org/10.1063/1.555755 Published Online: 15 October 2009 Wan Ying Shiu, and Donald Mackay ARTICLES YOU MAY BE INTERESTED IN A critical review of Henry’s law constants for chemicals of environmental interest Journal of Physical and Chemical Reference Data 10, 1175 (1981); https:// doi.org/10.1063/1.555654 Octanol-Water Partition Coefficients of Simple Organic Compounds Journal of Physical and Chemical Reference Data 18, 1111 (1989); https:// doi.org/10.1063/1.555833 Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and − hydroxyl radicals (⋅OH/⋅O in Aqueous Solution Journal of Physical and Chemical Reference Data 17, 513 (1988); https:// doi.org/10.1063/1.555805 Journal of Physical and Chemical Reference Data 15, 911 (1986); https://doi.org/10.1063/1.555755 15, 911 © 1986 American Institute of Physics for the National Institute of Standards and Technology. A Critical Review of Aqueous Solubilities, Vapor Pressures, Henry's Law Constants, and Octanol-Water Partition Coefficients of the Polychlorinated Biphenyls Wan Ying Shiu and Donald Mackaya) Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Canada lW5S lA4 Relationships between the environmentally relevant physical chemical properties of the polychlorinated biphenyls, namely, aqueous solubility, vapor pressure, Henry's law con­ stant, and octanol-water partition coefficient are discussed. Reported experimental data are tabulated and critically reviewed. Recommended values are given for 42 of the 209 congeners; however, procedures are suggested for estimating the properties of the other congeners. Properties of mixtures are not treated. Key words:. critically reviewed data; Henry's law constant; octanol-water partition coefficient; polychlorinated biphenyl (PCB); PCB, solubility; vapor pressure. Contents 1. Introduction ......................................................... 911 4; Octanol-water partition coefficients (log K ow ) 2. Physical Chemical Property Relationships.. ........ 913 for PCB congeners at 25°C.. ......... ....... ................ 920 3. Physical Chemical Properties ..... ... .............. ........ 913 5. Vapor pressures and Henry's law constants for 4. List of Symbols.. ..... ......... ........ .... ..... ..... ....... ........ 928 PCB congeners at 25 °C ........ ..... ........ ...... ............ 923 5. Acknowledgments ......... ....... ... ....... ....... ....... ........ 928 6. Summary of selected property values of PCB con- 6. References.. ..... ......... ........ ................. .............. ..... 928 geners ................................................................... 927 List of Tables 1. Approximate percent composition of some com- List of Figures merical PCB products .......................................... 912 1. Plot oflog CL vs chlorine number ........ ........ ........ 918 2. Physical properties of some PCB congeners at 2. Plot oflog K ow vs chlorine number ................... 918 25 °C ..................................................................... 914 3. Plot OflOgPL vs chlorine number ........................ 919 3. Aqueous solubility of PCB congeners at 25 °C .... 916 4. Plot oflog Q vs chlorine number ...... ........ ........... 928 1. Introduction cachlorobiphcnyl. It is only rcccntly2 that all 209 congcncrS have been individually synthesized and characterized. The polychlorinated biphenyls (PCB's) are a group of The characteristic properties of the PCB's are hydro­ xenobiotic chemicals first manufactured commercially phobicity or lipophilicity (i.e., large octanol-water partition about 1930 and whkh were widely used as transfonm:::r cool­ coefficient and low aqueous solubility), relatively low vapor ants, dielectric fluids, solvents, and flame retardants until pressure, .and extreme resistance to chemical reaction. 3 restrictions on their use were.introduced in the early 1970s. 1 These properties result in persistence in the environment, a Of the approximately 570 000 000 kg sold in the U.S. as of tendency to accumulate in biota and in sediments, and the 1975, some 68000 000 kg were estimated to be mobile in the ability to be transported through the atmosphere to regions environment and some 130 000 ()()() kg were in landfills or remote from source discharges.4 For example, appreciable equipment dumps. There are 209 possible chlorinated bi­ concentrations are found in the soils, sediments, waters, phenyls ranging from the three monochlorobiphenyls to de- biota, atmosphere, and precipitation in the Great Lakes Ba­ 5 9 sin. - The biological and human health effects of PCB's have been reviewed recently.8 a) Person to whom correspondence should be addressed. The industrial chemical products are mixtures of nu­ merous congeners separated by distillation into defined boil­ @1986bytheU. s. Secretary of Commerce on behalfofthe United States. This copyright is assigned to the American Institute of Physics and the ing ranges. For example, the Aroclors manufactured by American Chemical Society. Monsanto were marketed in seven grades designated by a Reprints available from ACS; see Reprints List at back of issue. four digit number, the first two (usually 12, but in one case 0047-2689/86/020911-19/$06.00 911 J. Phys. Chern. Ref. Data, Vol. 15, No.2, 1986 912 W. Y. SM.U AND D. MACKAY TABLE l. Approximate percent compositon of some commercial PCB products (Ref. 1) Aroclor type or grade Kanechlors Penclors Chlorobjphenyl 1016 1221 1232 1242 1248 1254 1260 KC-300 KC-400 KC-500 OK C12H10 0.1 11 6 0.1 0.1 C1ZHgCI 51 26 0.1 C12HaCI 2 20 32 29 16 2 0.5 17 3 C12H7C13 57 4 24 49 18 60 33 5 C12H6CI 4 21 2 15 25 40 21 23 44 27 C12HSC1 S 0.5 0.5 36 48 12 0.6 16 55 C12H4CI 6 0.1 4 23 38 5 13 C12H3C1 '1 0.1 6 41 C12 HZC1 a C12HC1 g C1ZC1 10 100 10) designating the carbon number and the last two (e.g., vironmental fate of the PCB's is to' obtain properties for all 42) designating the mass percentage of chlorine. the congeners and treat each congener separately. Unfortu­ Table I (Ref. 1) gives the approximate percentage com­ nately, relatively few congeners have been synthesized in suf­ position of the Aroclors. At least nine other trade designa­ ficient quantities that property determinations have been tions have been used in various countries by various manu­ possible. Further, these determinations are experimentally facturers. demanding and many erroneous data exist. There is, how­ The presence of such a large number of congeners ever, a tendency for the congeners to have properties which renders chemical analysis and reporting very difficult. A vary systematically with chlorine number, thus the proper­ common practice has been to report environmental concen­ ties of one congener can be estimated from those of another. tration in terms of an Aroelor grade equivalent, but this This estimation requires that all available property data be practice is imprecise because the environmental distribution gathered, critically reviewed, and "best" values assigned. of congeners differs from the commercial grade distribution. The assigned values of solubility (c), octanol-water parti­ It is likely that there is differential transport, reaction, and tion coefficient (K ow ), vapor pre~~l1re (p), and Henry'~ law accumulation between congeners. Further, to elucidate the constants (H) should be internally consistent. For example, environmental transport and transformations of a mixture H, is equal topic, andcandK ow are related inversely. Typi­ requires that the mixture be assigned properties such as a cally, substitution of one chlorine atom for a hydrogen unique solubility or vapor pressure. Such an assignment is causes p and c to fall by a factor of 3 to 4, K ow to rise ·by a fundamentally erroneous because a mixture does not have similar factor, while H remains relatively constant. This en­ unique phase eqUilibrium physical chemical properties. The ables estimates to be made of properties of one chlorine num­ reported measured solubilities or vapor pressures can only ber group from another. The congener properties depend not be regarded as some average of the properties of the individ­ only on chlorine number, but on the configuration. It is thus ual PCB congeners. desirable to develop "rules" for estimating properties as a It has become increasingly accepted that the only rigor­ function of chlorine arrangement as well as chlorine num­ ous method of addressing the problem of calculating the en- ber. This is presently impossible, but some progress has been J. Phys. Chern. Ref. Data, Vo•• 15, No.2, 1986 PHYSICAL CHEMICAL PROPERTIES OF POLYCHLORINATED BIPHENYLS 913 made recently in identifying characteristic groupings which between the aqueous solubility and octanol-water partition 17 cause, for example, unusually large K ow values.6 coefficient. 13,16-19 Mackay et al. 16 and Banetjee et al. have In this study we gather and critically review the avail­ suggested that the product Q of K ow and the subcooled liq­ able data for PCB congeners and assign selected values uid solubility CL is relatively constant. More recently, based where possible. Sufficient data exist for assessing only 42 of on the measurement of CL and K ow of a wide range of PCB the 209 congeners; however, it is hoped that in the future congeners by Miller et al.,13 it has
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