Structure-toxicity relationships for phenols
- Univ. of Tennessee, Knoxville, TN (United States)
- Oak Ridge National Lab., TN (United States). Environmental Science Div.
Toxicity values for 45 phenols tested in the 2-d static population growth inhibition assay with the ciliate Tetrahymena pyriformis were tabulated. Each chemical was selected so the series formed uniform coverage of the hydrophobicity/ionization surface. A high quality hydrophobicity-dependent (log K{sub ow}) structure-toxicity relationship (log IGC{sub 50}{sup {minus}1} = 0.737 (log K{sub ow}) {minus} 1.440; n = 15, r{sup 2} = 0.093, s = 0.103, F = 758.29, Pr > F = 0.0001) was developed for phenols with pK{sub a} values > 9.4. Similarly, separate hydrophobicity-dependent relationships were developed for phenols with pK{sub a} values of 4.0, 5.1, 6.4, 7.5, and 8.7. Comparisons of intercepts and slopes, respectively, revealed phenols with pK{sub a},, values of 6.4 to be the most toxic and the least influenced by hydrophobicity. These relationships are reversed for the more acidic and basic phenols. Plots of toxicity versus pK{sub a} for nitro-substituted phenols and phenols with log K{sub ow} values of either 1.75 or 2.50 further demonstrated the parabolic relationship between toxicity and ionization constant. In an effort to more accurately model the parabolic-like relationship between toxicity and ionization, the bilinear function {vert_bar} 6.4 {minus} pK{sub a} {vert_bar} was used to model ionization effects for derivatives with pK{sub a} values of between 3.4 and 9.4. For derivatives with pK{sub a}, values < 3.4 and > 9.4, a value of 3.00 was used to quantitate ionization effects. The use of log K{sub ow} in conjunction with this modified pK{sub a} ({Delta} pK{sub a}) resulted in the structure-toxicity relationship (log IGC{sub 50}{sup {minus}1} = 0.574 (log K{sub ow}) {minus} 0.273 ({Delta} pK{sub a}) + 0.078; n = 45, r{sup 2}=0.902, s = 0.264, F = 193.06, Pr > F = 0.0001).
- OSTI ID:
- 382732
- Report Number(s):
- CONF-9511137--; ISBN 1-880611-03-1
- Country of Publication:
- United States
- Language:
- English
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