Relation between the chemical structures of chlorophenols and their dissociation constants and partition coefficients in several solvent-water systems

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War. Res. Vol.28, No. 7, pp. 1547-1552,1994 Copyright © 1994ElsevierScienceLtd Printed in Great Britain.All rights reserved 0043-1354/94$7.00+ 0.00

RELATION BETWEEN THE CHEMICAL STRUCTURES OF CHLOROPHENOLS AND THEIR DISSOCIATION CONSTANTS AND PARTITION COEFFICIENTS IN SEVERAL SOLVENT-WATER SYSTEMS TAKUOK1SHINOl O and KUNIOKOBAYASHI2~ IEnvironmental Science Laboratory, Ube College, 5-40 Bunkyochyo, Ube 755 and 2Water Supply Authority of Southern Fukuoka Prefecture, Araki-machi, Kurume 839-01, Japan (First received March 1993; accepted in revised form November 1993)

Abstract--The partition coefficientsand dissociation constants (as PKa) ofchlorophenols were determined, using n-heptane and n-octane as non-hydrogen bonding solvents, and 1-octanol and n-heptane containing lecithin as hydrogen bonding solvents. The coefficients of chlorophenols in n-heptane-water were almost the same values as those in n-octane-water. A good correlation of r = 0.996 was observed between the coefficientin l-octanol-water and that in n-heptane containing lecithin-water. However, the correlation between the coefficient in n-octane-water and that in l-octanol-water was a little low (r = 0.885) compared with the above value, and that between n-heptane--water and n-heptane containing lecithin-water was also a little low (r = 0.890). The partition coefficients of chlorophenols in the solvent-water systems increased with increasing number of chlorine atoms. In chlorophenols having the same number of chlorine atoms, their partition coeffÉcientsin hydrogen bonding solvent-water decreased in the order of non-, mono- and di-orthochlorophenols, whereas the coefficients in non-hydrogen bonding solvent-water increased in the above order. This fact must be attributed to the formation of intramolecular hydrogen bonding between the chlorine atom substituted at the ortho-position and the OH group in the chlorophenols. The pKa values of chlorophenols decreased with increasing number of chlorine atoms, and also with the closing of the chlorine atom position to the OH group in chlorophenols having the same number of chlorine atoms. Key words--partition coefficient, dissociation constant, chlorophenols, chemical structure, hydrogen bonding, lecithin

INTRODUCTION

The partition coefficient and dissociation constant play an important role in estimating the environmental fate and biological activity of chemicals. The partition coefficient of the l-octanol-water system has been recognized as a good indicator for the transport of chemicals to the site of action in vivo (Hansch and Dunn, 1972; Rogers and Wong, 1980). Hansch and Dunn (1972) suggested that the OH function of octanol, which can act as a hydrogen bonding donor as well as an acceptor, seems reasonable for a model of macromolecules which have an abundance of OH groups for hydrogen bonding throughout the largely apolar milieu. It is considered that the hydrogen bonding ability of the OH group in l-octanol with chemicals contributes to the estimation of the magnitude of the biological activity of the chemicals. Kobayashi and Kishino (1980) reported that the accumulation of PCP by fish abruptly decreases with an increase of the pH of the PCP media, and

consequently the PCP concentration in the fish body does not readily reach a lethal level (about 100/tg/g body weight) at a higher pH, resulting in the reduction of the toxicity of PCP to fish. In our previous paper (Kobayashi et al., 1979), it was also demonstrated that an increase of the chlorine atom number in chlorophenols promotes an accumulation of chemicals in fish and leads their concentrations to a certain lethal level (roughly 100-200#g/g body weight), and consequently causes an abrupt increase in toxicity to fish. It is also well known that the toxicity of chloropbenols to organisms significantly depends on the substituted position of the chlorine atom (Blackman et al., 1955; McLeese et al., 1979; Liu et al., 1982; Borzelleca et aL, 1985; Tissut et al., 1987; DeMarini et al., 1990). A relation between the chemical structure and their toxicity has been analyzed using physico-chemical properties such as partition coefficient, dissociation constant and so on, but little information has been obtained on the mechanism resulting in the above relation.

1547

1548

TAKUO KISHINO and KUNIO KOBAYASHI

The present study was carried out to examine the effect of the position and n u m b e r of chlorine atoms in chlorophenols on their dissociation constants and partition coefficients in solvent-water systems, focusing on the hydrogen bond f o r m a t i o n between l-octanol and chlorophenols. Phospholipids such as lecithin a n d cephalin a n d so on, which are a m a j o r c o m p o n e n t of lipids in the cell m e m b r a n e , play an i m p o r t a n t role in the m e m b r a n e permeability of chemicals. Therefore, the contribution of lecithin to the transfer o f chlorophenols from water to organic solvents was examined, t h r o u g h the relation between the partition coefficient in n - h e p t a n e containing lecithin-water and t h a t in 1 -octanol-water. MATERIALS AND METHODS

Chemicals' Phenol and twelve chlorophenols were used in this study as follows; 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), 2,4dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP), 2,6-dichloropbenol (2,6-DCP), 3,5-dichlorophenol (3,5DCP), 2,4,5-trichlorophenol (2,4,5-TCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TCP) and pentachlorophenol (PCP). Phenol, 2-CP and 4-CP were obtained from Wako Pure Chemical Industries Ltd, Osaka, Japan and the other chlorophenols from Tokyo Chemical Industry Co. Ltd, Tokyo, Japan. The purities of phenol, 2-CP, 4-CP, 2,3-DCP, 2,4-DCP and 2,5-DCP were confirmed to be about 100% by gas chromatography after monochloroacetylation (Kishino, 1989). After purifying 3-CP by distillation (b.p. 214-217°C), 2,6-DCP, 3,5-DCP, 2,4,5-TCP, 2,4,6-TCP and 2,3,4,6-TCP by recrystallization from ligroin, and PCP from benzene, the purities of their chemicals were also confirmed to be about 100% by the same gas chromatography as the procedure described above. n-Heptane and n-octane were used as non-hydrogen bonding solvents, and l-octanol and n-heptane containing lecithin as hydrogen bonding solvents. These organic solvents and the lecithin (from egg) are special and analytical grade reagents produced by Wako Pure Chemical Industries, Ltd, respectively. Possible mechanism of distribution of chlorophenols between organic solvent and water On the assumption that a weak acid (HA) such as chlorophenol is monomeric in both organic solvent and water phases and its unionized form alone transfers from water to solvent, the distribution ratio (D) and partition coefficient (P) of HA between solvent and water, and the dissociation constant (Kd) are expressed by the following equations, respectively. D

[HA]°rg [HA]~ + [A l~ P - [HA]°~g [HA],~

K,, =

[H+ L[A 1~ ......... [HA]~.

1) (2)

(3)

Substituting equations (2) and (3) into equation (1) gives the following: [H ~L D= P . . . . K~ + [H+]~

(4)

When [H+]w>>K,, i.e. pH<
(5)

When [H+]w<>pK,, equation (4) can be expressed as D = P" [H--+]-Y

K,

(6)

Taking logarithms, equation (6) can be expressed as log D = log P + pK, - pH

(7)

Thus, D in the region of pH<>pK,, log D should decrease linearly with a slope of - 1 as pH increases.

Determination of partition coefficients in organic solventwater systems Each chlorophenol solution (37.5 #M) at various pHs was prepared with the following buffer solutions: M/50 sodium acetate for pH 3, 4, 5 and 5.5; M/50 Na2HPO 4 for pH 6, 7 and 8; and M/50 Na2CO 3 for pH 9 and 10, adjusting their respective pH values with I M solution of HCI or NaOH. An appropriate amount of the solution was shaken with each proper amount of n-heptane, n-octane and l-octanol at 19-21°C for 15 min. It was previously confirmed that the distribution of the tested chlorophenols between the solvents and water attains equilibrium within 10 rain. After removing the emulsion in the water layer by centrifugation (3000 rpm) and standing overnight, the concentration of each chlorophenol in the water phase was determined by the 4-aminoantipyrine method or gas chromatography (ECD) after monochloroacetylation (Kishino, 1989). The concentration of each chlorophenol in the solvent phase was calculated from the amount decreased in the water phase. The distribution ratios of the chlorophenols between each solvent and water were obtained as the ratio of the concentration in each solvent to that in the water. The partition coefficients of the chlorophenols in each solvent-water system were obtained as the distribution ratios in the range of pH < pK, - 1 according to equation (5). An appropriate amount of each chlorophenol solution was mixed using a stirrer with n-heptane solution containing 5% lecithin at 19-21'C for 24 h, because shaking of the mixture caused heavy emulsification. In a preliminary experiment, the distribution of the tested chlorophenols between the solvent and water was confirmed to reach equilibrium at 13-h stirring. The distribution ratios and partition coefficients of the chlorophenols in the solvent-water were determined using the same procedure as described above. Determination of' dissociation constants Rearranging equation (7) gives the following: pK a = pH - log P + log D

(8)

The dissociation constants (as pK~) of the chlorophenols were determined by substituting the partition coefficients (as log P ) and distribution ratios (as log D ) at various pHs into equation (8). RESULTS AND DISCUSSION

Effect of the characteristics o f the organic solvent on the distribution ratios o f chlorophenols The change in the P C P distribution ratio between water and each solvent of n-heptane, l-octanol a n d n - h e p t a n e containing 5 % lecithin in the pH range from 3 to 10 is shown in Fig. 1. The ratios in the n - h e p t a n e - w a t e r system at the respective pHs obey e q u a t i o n (4) derived by assuming that P C P in b o t h the solvent a n d water layers is m o n o m e r i c and the

Partition coefficient and pKa of chlorophenols

ionized forms of the chemicals having low lipid solubility show a marked increase in transfer from the water phase to the chloroform phase containing lecithin at the physiological pH of the small intestine. This result demonstrates that lecithin contributes to the transfer of the ionized PCP from water to non-hydrogen bonding solvents such as n-heptane and n-octane. Figure 2 shows the change in distribution ratio of each chlorophenol between water and each solvent of n-heptane, 1-octanol and n-heptane containing lecithin in the pH range from 3 to 10. The ratios of all the chlorophenols in the n-heptane-water system obeyed equation (4) at all pHs. In analogy with PCP, however, the ratios of 2,4,6-TCP and 2,3,4,6-TCP in both systems of l-octanol-water and n-heptane containing lecithin-water showed higher values than those estimated from equation (7) at pHs over 8.

6 5 4 3 2 1 0 -1

-2 t

-3

t

i

i

i

a

|

i

|

2 3 4 5 6 7 8 9 1011

pH Fig. 1. Effect of pH and the kind of organic solvent-water system on the distribution ratio (D) of PCP. The dashed line in the figure is based on the assumption that PCP in both the organic solvents and the aqueous phase is monomeric and that only the unionized PCP is transferred from the water to the solvents.

Relation between the chemical structure o f chlorophenols and their partition coefficients in solvent-water systems

unionized form alone transfers from the water to the solvent. This result proves that the unionized PCP alone transfers from the water to the non-hydrogen bonding solvent. However, the ratios in both systems of l-octanolwater and n-heptane containing lecithin-water were higher than those estimated from equation (7) above pH 8 in the former system and above pH 7 in the latter system, respectively. In our previous paper (Kishino and Kobayashi, 1980), it was demonstrated that not only the unionized form but the ionized form of PCP transfers from the water to the hydrogen bonding solvents such as 1-octanol, l-heptanol and l-nonanol. According to Furusawa et al. (1972), the

Phenol

I-CP

1549

The partition coefficients of chlorophenols in four solvent-water systems are summarized in Table 1. All values of the partition coefficients in l-octanol-water obtained in this study were in good agreement with those values in the published literature (Saarikoski and Viluksela, 1982; Lipnick et al., 1985; Moulton and Schultz, 1986). The good agreement supports the validity of the determination procedure used in this study. The partition coefficient in each solvent-water system increased with the increase in the number of substituted chlorine atoms, except those of 3,5-DCP in both systems of n-heptane-water and n-octane-water. The coefficients of chlorophenols in

4-CP

l-CP

Q -2 ,

,

,

i

,

J

J

,

i

i

,

,

J

,

.

,

,

,

.

,

.

%

.

o)

3

2,6-DCP

2,6-DCP

3,$-DCP

2,4,I-TCP

2,4,6-TCP

2,S,4,I-TCP

4

2 0 -2 5

7

9

11

5

7

9

11

5

7

9

11

5

7

9

11

4

6

8

1

4

6

8

Im Fig. 2. Effect of pH and the kind of organic solvent-water system on the distribution ratio (D) of phenol and chlorophenols. - - O - - , l-Octanol-water; - - & - - , n-heptane containing 5% lecithin-water; - - O - - , n -heptane-water.

10

1550

TAKUO KISH1NOand KUNIO KOBAYASHI Table 1. The partition coefficientsin n-heptane-water, n-octane-water, I-octanol water and n-heptane containing 5% lecithin-water systems n-Heptane n-Octane l-Octanol n-Heptane containing Chemical -water -water water 5*/0 lecithin--water Phenol - 1.03 -0.99 1.57 (I .46*) 0.24 2-CP 3-CP 4-CP

0.76 - 0.32 - 0.40

0.74 -0.31 - 0.41

2.29 (2.15") 2.64 (2.50*) 2.53 (2.39*)

1.16 1.27 1.26

2,3-DCP 2,4-DCP 2,5-DCP 2,6-DCP 3,5-DCP

1.32 1.25 1.35 1.45 0.41

1.27 1.21 1.31 1.48 0.41

3.26 (3.19t') 3.20 (3.06*) 3.36 (3.06*) 2.92 (2.84~) 3.60 (3.52t)

2.05 2.03 1.98 1.65 2.27

2,4,5-TCP 2,4,6-TCP

1.79 2.09

1+76 2.05

4.02 (3.72*) 3.67 (3.69*)

2.84 2.55

2,3,4,6-TCP

2.64

2.58

4.24 (4.10")

2.99

PCP 3.12 3.18 5.02 (5.12*) 3.79 The values in the table are expressed as log of the partition coefficient. *Lipnick et al. (1985). tMoulton and Schultz (1986). :~Saarikoski and Viluksela (1982).

the n - h e p t a n e - w a t e r system were almost the same as those in n - o c t a n e - w a t e r . A good correlation of r = 0.996 was also observed between the coefficient in 1-octanol-water a n d that in n - h e p t a n e containing lecithin-water. However, the correlation between the coefficient in n - o c t a n e - w a t e r a n d that in l - o c t a n o l water was a little low (r = 0.885) c o m p a r e d with the above value, and that between n - h e p t a n e - w a t e r a n d n - h e p t a n e containing lecithin-water was also a little low (r = 0.890). As shown in Table 1, b o t h partition coefficients in the n - h e p t a n e - w a t e r a n d n - o c t a n e - w a t e r systems increased in the order of 3 - C P - 4 - C P < 2 - C P in m o n o c h l o r o p h e n o l s , 3,5-DCP < 2 , 3 - D C P - 2 , 4 D C P - 2 , 5 - D C P < 2,6-DCP in dichlorophenols and 2,4,5-TCP < 2,4,6-TCP in trichlorophenols, whereas b o t h partition coefficients in the l - o c t a n o l - w a t e r a n d n - h e p t a n e containing lecithin-water systems decreased in the a b o v e - m e n t i o n e d order, respectively. These results d e m o n s t r a t e that the partition coefficients of chlorophenols in n o n - h y d r o g e n b o n d i n g solvent-water systems increase in the order of nono r t h o c h l o r o p h e n o l s , m o n o - o r t h o c h l o r o p h e n o l s and di-orthochlorophenols, whereas the coefficients in the hydrogen b o n d i n g solvent-water systems decrease in the above order, i.e. the hydrogen b o n d i n g ability o f chlorophenols falls in the same order as described above. The partition coefficients in 1-octanol-water and those in n - o c t a n e - w a t e r are correlated in Fig. 3, relating to the position of the chlorine a t o m substituted. Parallel linear relationships were observed a m o n g the groups of non-, m o n o - and diorthochlorophenols. Fujita et al. (1977) reported that a linear relationship between the partition coefficients of m o n o s u b s t i t u t e d benzenes in c h l o r o f o r m - w a t e r a n d those in l - o c t a n o l - w a t e r is observed in each group of chemicals with and without the substituent

hydrogen b o n d i n g g r o u p in parallel. It is well k n o w n that the lowest boiling point of 2-CP a m o n g m o n o c h l o r o p h e n o l s (2-CP, b.p. 174.5°C; 3-CP, b.p. 214°C; 4-CP, b.p. 218°C) is attributed to the form a t i o n o f intramolecular hydrogen b o n d i n g between the chlorine a t o m substituted at the o r t h o - p o s i t i o n a n d the O H group. Such a n intramolecular hydrogen b o n d is also formed in b o t h organic solvents a n d water (Burton et aL, 1964; Pauling, 1960). The chlorine a t o m substituted at the o r t h o - p o s i t i o n significantly reduces the electron density of the O H group more t h a n the chlorine a t o m s substituted at the o t h e r position. Therefore, the m a g n i t u d e of for-

A

4 ~

1013~712 8 11 BC

3

O.

-1 -2 1

I

I

I

I

I

I

2

3

4

5

6

7

Log P ( 1 - ~ l ~ a t e r )

Fig. 3. Relation between the partition coefficients (P) of phenol and chlorophenols in 1-oetanol-water and those in n-octane-water relating to the position of the substituted chlorine atom. (A) Chlorophenols having chlorine atoms substituted at the 2,6-positions of phenol; (B) ¢hlorophenols having a chlorine atom substituted at the 2-position of phenol; (C) chlorophenols having no chlorine atom substituted at the 2- or 2,6-positions of phenol. (1) Phenol; (2) 2-CP; (3) 3-CP; (4) 4-CP; (5) 2,3-DCP; (6) 2,4-DCP; (7) 2,5-DCP; (8) 2,6-DCP; (9) 3,5-DCP; (10) 2,4,5-TCP; (I 1) 2,4,6-TCP; (12) 2,3,4,6-TCP; and (13) PCP.

1551

Partition coefficient and pK, of chlorophenols mation of the intramolecular hydrogen bonding in di-orthochlorophenols is thought to be more than that in mono-orthochlorophenols. As shown in Fig. 4, the same parallel relationship as that in Fig. 3 was also observed between the partition coefficients in n-heptane containing lecithin-water and those in n-heptane-water. Consequently, the decrease of the partition coefficients in the order of non-, mono- and di-orthochlorophenols in hydrogen bonding solvent-water systems proved to be attributed to the decrease of their intermolecular hydrogen bonding ability of the OH group in that order. This is because the OH group forming intramolecular bonding with the chlorine atom substituted at the o r t h o - p o s i t i o n is not able to form intermolecular hydrogen bonds with solvents. From the above discussion, it is also presumed that the formation of intermolecular hydrogen bonds between lecithin and the OH group in chiorophenols plays an important role in the transfer of chemicals from water to solvents. Relation between the chemical structures o f chlorophenols a n d their dissociation constants

The distribution ratios of all chlorophenols used in this study in the n-heptane-water system obeyed equation (4). The dissociation constants (as pK,) of chlorophenois shown in Table 2 were calculated by substituting the distribution ratios at various pHs and partition coefficients found in the n-heptane-water system into log D, pH and log P in equation (8), respectively. All values of the dissociation constants obtained in this study were in good agreement with those values in the published literature (Blackman et al., 1955; Hammers et al., 1982; Lipnick et al., 1985). The pK, values of the chlorophenols decreased with increasing number of chlorine atoms substi4

J.

3

J

J 13.

2

s

7

A

Io

C

1 0 -1

-2 -3 -1

I

I

I

I

I

!

0

1

2

3

4

5

Log P (n-heptane containing 5% lecithin/water)

Fig. 4. Relation between the partition coefficients (P) of phenol and chlorophenols in n-heptane containing lecithin-water and those in n-heptane-water relating to the position of the substituted chlorine atom. The symbols in this figure, i.e. the letter of the alphabet and the numbers, are the same as those in Fig. 3.

Table 2. The dissociationconstants of phenol and chlorophenols Chemical pK, Phenol 9.9 (9.9*) 2-CP 3-CP 4-CP

8.3 (8.5]') 8.9 (9.It) 9.2 (9.4t)

2,3-DCP 2,4-DCP 2,5-DCP 2,6-DCP 3,5-DCP 2,4,5-TCP 2,4,6-TCP

7.6 (7.75) 7.8 (7.8*) 7.3 (7.5t) 6.6 (6.8t) 8.1 (8.2~:) 6.9 (7.0*) 6.0 (6.1*)

2,3,4,6-TCP

5.2 (5.3*)

PCP 4.7 (4.8*) *Blackmanet al. (1955). tLipnick et aL (1985). :~Hammerset al. (1982). tuted, and also with the closing of the chlorine atom position to the OH group in chlorophenols having t h e same number of chlorine atoms substituted. CONCLUSION The effect of the position and number of chlorine atoms in chlorophenols on their dissociation constants and partition coefficients in solvent-water systems was examined. The partition coefficients were determined using n-heptane and n-octane as nonhydrogen bonding solvents, and 1-octanol and nheptane containing 5% lecithin as hydrogen bonding solvents. The major results and conclusions are as follows. (1) The pKa values of the chlorophenols decreased with increasing number of chlorine atoms, and also with the closing of the chlorine atom position to the OH group in chlorophenols having the same number of chlorine atoms. (2) The partition coefficients in each solvent-water system increased with an increase in the number of chlorine atoms. (3) In chlorophenols having the same number of chlorine atoms, their partition coefficients in the hydrogen bonding solvent-water system decreased in the order of non-, mono- and di-orthochlorophenols, whereas the coefficients in the non-hydrogen bonding solvent-water system increased in the above order. (4) A good correlation was observed between the partition coefficients of chlorophenols in both n-heptane and n-octane-water systems, and also between those in both 1-octanol and nheptane containing 5% lecithin-water systems. (5) A linear relationship between the partition coefficient in the non-hydrogen bonding solvent-water system and that in the hydrogen bonding solvent-water system was observed in each group of non-, mono- and diorthochlorophenols in parallel.

1552

TAKUO KISHINOand KuNIo Kon,~Y,~sm

F r o m these results, it is concluded that the decrease of the partition coefficients in the order of non-, m o n o - and d i - o r t h o c h l o r o p h e n o l s in the hydrogen b o n d i n g solvent-water systems is attributed to the decrease of the intermolecular hydrogen bonding ability of the O H group in that order, and that the formation of the intermolecular hydrogen b o n d i n g between lecithin and the O H group in chlorophenols plays an i m p o r t a n t role in the transfer of chemicals from water to solvents. A l t h o u g h a n u m b e r of studies have been performed on the relation between the toxicity and the substituted position of the chlorine atom of chlorophenols, the mechanism resulting in the relation has not been clearly demonstrated. This study will contribute to the elucidation of the mechanism of the occurring toxicity through a relation between the chemical structure and toxicity analyzed by using physicochemical properties such as dissociation c o n s t a n t a n d partition coefficient in several solvent-water systems.

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Fujita T., Nishioka T. and Nakajima M. (t 977) Hydrogenbonding parameter and its significance in quantitative structure-activity studies. J. Med. Chem. 20, 10714081. Furusawa S., Okumura K. and Sezaki H. (1972) Enhanced migration of the ionized forms of acidic drugs from

water into chloroform in the presence of phospholipids. J. Pharm. Pharmac. 24, 272-276.

Hammers W. E., Meurs G. J. and De Ligny C. L. (1982) Correlations between liquid chromatographic capacity ratio data on lichrosorb RP-18 and partition coefficients in the octanol-water system. J. Chromatogr. 247, 1-13. Hansch C. and Dunn W. J. III (1972) Linear relationships between lipophilic character and biological activity of drugs. J. Pharm. Sci. 61, 1 19. Kishino T. (1989) Studies on the action mode of chlorophenols in fish. Doctoral thesis, Kyusyu University, Fukuoka, Japan. Kishino T. and Kobayashi K. (1980) A study on the absorption mechanism of pentachlorophenol in goldfish relating to its distribution between solvents and water. Nippon Suisan Gakkaishi 46, 1165-1168. Kobayashi K. and Kishino T. (1980) Effect of pH on the toxicity and accumulation of pentachlorophenol in goldfish. Nippon Suisan Gakkaishi 46, 167 170. Kobayashi K., Akitake H. and Manabe K. (1979) Relation between toxicity and accumulation of various chlorophenols in goldfish. Nippon Suisan Gakkaishi 45, 173-175. Lipnick R. L., Bickings C. K., Johnson D. E. and Eastmond D. A. (1985) Comparison of QSAR predictions with fish toxicity screening data for 110 phenols. A S T E M Spec. "l~,eh. Publ., Aquat. Toxieol. Hazard Assess. 891, 153-176. Liu D., Thomson K. and Kaiser K. L. E. (1982) Quantitative struclure toxicity relationship of halogenated phenols on bacteria. Bull. envir. Contain. Toxicol. 29, 130 136. McLeese D. W., Zitko V. and Peterson M. R. (1979) Structure lethality relationships for phenols, anilines and other aromatic compounds in shrimp and clams. Chemosphere 2, 53 57. Moulton M. P. and Schultz T. W. (1986) Comparisons of several structure toxicity relationships for chlorophenols. Aquat. Toxicol. 8, 121 128. Pauling L. (1960) The Nature (~['the Chemical Bond (Translated by Koizumi M. in 1969), pp. 438-450. Kyoritsushuppan, Tokyo (in Japanese). Rogers J. A. and Wong A. (1980) The temperature dependence and thermodynamics of partitioning of phenols in the n-octanol water system. Int. J. Pharm. 6, 339-348. Saarikoski J. and Viluksela M. (1982) Relation between physicochemicat properties of phenols and their toxicity and accumulation in fish. Ecotoxic. ent, ir. Safety 6, 501 512. Tissut M., Tillandier G., Ra~anel P. and Benoit-Guyod J. L. (1987) Effects of chlorophenols on isolated class A chloroplasts and thylakoids: a QSAR study. EcotoxicoL envir. Salety 13, 3242.