The octanol-water partitioning of some hydrophobic and hydrophilic compounds

Chemosphere,Vol.12,No.7/8,pp Printed in G r e a t B r i t a i n

1107-1111,1983

0045-6535/83 $ 3 . 0 0 + .00 ©1983 Pergamon Press Ltd.

THE OCTANOL-WATER PARTITIONING OF SOME HYDROPHOBIC AND HYDROPHILIC COMPOUNDS

R.F. Platford

Canada Center for Inland Waters, Burlington, Ontario,

Canada L7R 4A6

ABSTRACT

Octanol-water partition coefficients, K, have been collected for 15 representative compounds having a logarithmic range of values of K from +5 to -5. In spite of the wide variation of structural types, there is an inverse correlation between log K and the log of the water solubility. Triolein-water partition coefficients were slightly higher than the K values for the same compounds.

INTRODUCTION

Hydrophobicity is an important feature in the biological transport of physiologically agents because

(1,2,3,4).

There

are

of their solubility

pertinent

hydrophilic

compounds

which

in water as well as in organic solvents,

partitioning of a few of them,

One of these, silver perchlorate,

deserve

study,

active

however,

and here I report on the

is soluble to the extent of 84

weight percent in water and represents an extreme example of a compound which is very soluble in water but which is also soluble in several organic solvents.

METHOD

The

partition

described

coefficients

in previous

papers

for

solutes

between

n-octanol

in this series

(5,6,7),

or were

1107

and

water

were

determined

taken from the literature.

as Four

1108

new

octanol-water

trioleate The

coefficients

(triolein) and water.

compounds

described rubber

partition

used here,

therein.

Of

vulcanization

the

was 0.II g %-i at 22°C. Mellitic acid

measured,

alon~ with

two new

In all cases, both phases were analyzed

but studied newly

in my previous

investigated

accelerator

crystals melting at 42°C;

were

(8),

was

its solubility

papers,

compounds,

recrystallized

in octanol

ones

for glyceryl

for the solute.

were prepared

and purified

methylthiobenzothiazole from

methanol

and

as

(MTBT),

dried

to

was 240 g %-i and its solubility

a

give

in water

Analysis was by gas chromatography with an electron capture detector.

(MA) will be reported on in detail

elsewhere

(9).

A constant

value

for the

o ctanol-water partition coefficient was obtainable for this compound only by assuming a dime rization constant in the octanol phase of 625 molar -I. associate

even

more

3300 molar -I.

strongly

in

The above mentioned

and standard thiocyanate solution, The (I0).

paraquat

dichloride

Partitioning

was

the

octanol

Likewise, phase,

silver perchlorate was

with

two compounds were analysed

a

dimerization

found to

constant

by titration with standard

of base

respectively. the

measurements

same

as

that used

in

a previous

were made with a dilute aqueous

study

phosphate

of

this

compound

buffer solution

of

pH 7.4 and of low enough concentration so as not to interfere with the determination of chloride by titration with standard silver solution. on by H i r o m et al.

Compound

14, paraquat diiodide,

has been reportted

(13).

RESULTS AND DISCUSSION

The octanol-water values

for

a

few

partition

related

coefficients

compounds

octanol as a solute was calculated with

water)

K = 3.17).

to

the

solubility

Collander's

water between octanol

(II)

of

from

are

the

reported

from the ratio of the octanol

in

log K is 3.15.

in

literature

water;

Table

| and

"self molarity" my

Similarly,

Fig.

(3,5,6,7,11,12,13).

own

value

I, along The

of octanol

is

6.1

with

value

for

(saturated

M/0.0041

M

(log

I found the ratio of the molarity

and water to be 1.9 M/55 M, giving

log K = -1.46 for water.

of

Hansch and

Leo (3) record a value of -1.38. It two

is noteworthy

compounds

are

that water

relatively

is fairly

insoluble

soluble

in water.

measurements reported in the previous paragraph, a solute in triolein,

in both octanol and triolein although I have

and in oleic acid, its hydrolysis

isopiestic method (5) are given in Table 2.

therefore

a few measurements product.

made,

in addition

these to

the

in which water is treated as The results,

measured

by the

1109

6

I

I

I

I

I

I

1

I

!

I

11::~ 2

6•:7E)~ •

2

_go

89

C~lO

0

W [] -D iI

11

-2

I

-4

13

~e~

14E~

-6

I

I

10 100 I~g/kg

I

I

I

I

10 100 mg/kg

I

I

I

10 100 1000 g / k g water

Fig. 10ctanol-water partition coefficients (--) and triolein-water partition coeffients (X). I, DDT; 2, Hexachlorobenzene; 3, n-hexane; 4, Lindane; 5, Methylthiobenzothiazole; 6, n-Octanol; 7, Carbon tetrachloride; 8, Benzene; 9, Benzoic acid; 10, Caffeine; W, water; 11, Mellltic acid; 12, Silver perchlorate; 13, Paraquat dichloride, pH 7.4; 14, Paraquat diiodide, pH 7.4. Rectangles indicate water solubilities and all concentrations are per kilogram of solution (usually at

25oc).

iii0

TABLE 1

Octanol-water partition coefficients,

Compound (Fig. I) I 2, 3, 4, 5 6, 7 8, 9 10, W, 11, 12, 13, 14,

DDT HCB* Hexane Lindane MTBT Octanol CC14 Benzene Benzoic acid Caffeine Water Mellitic acid AgCI04 Paraquat (CI) Paraquat (I)

K, for several compounds at 20-25°C.

Water Concentration ~g kg -I

Log K

0.3-(2)** 0.3-(5) (1.4 x 104 ) 2-(I04] i0-( i0 J) (5.4 x 105 ) (0.8 x 106 ) (1.2 x 106 )

5.1+_0.1 5.2-+0 .i 3.9-+0.1 3.0-3.7 3.0-3.3 3.16_+0.01 2.6-+0.2 2.1-+0.2

(5 kg!~6)

19s

g (211 i0 J 3-I 50(490) 6-460(845) 30-(550) 5

0.01 -I .4 -i. 88_+0.03*** -2.64_+0.04*** -4.22_+0.05 -5.00

Reference

(7) (7) (5) (6) Present Present (11)

(5) (5) (3) (12) Present

(3)

(9) Present Present

(13)

* Hexachlorobenzene; see text for other compound abbreviations ** Solubilites given in parentheses *** Corrected for dimerization in octanol according to 2MA + (MA)2

Table 2.

Water solubility in lipid analogues,

Solvent Octanol Oleic Acid Oleic Acid-Triolein Triolein

From these results

in moles of water per dm 3 of solution.

Temperature 20°C 1.9 0.19

10°C 2.0 0.13 . . 0.051

(3:1 Mole ratio)

.

37°C -0.26 0.25 0.10

. 0.072

the log K values for solute water between octanol,

and water can be estimated;

they are,

respectively,

oleic acid,

-1.46, -2.46 and -2.9.

and triolein

The log K for para-

quat dichloride between triolein and water also was measured because of its physiological tance;

it was

-3.9.

The

triolein

values were

previously measured values for hexane, Except

for

the

case

of

plotted

from those in octanol by only +0.3 on average,

already

lipid,

although

made by others

water solubility, tic

compounds,

because

of their

compounds.

rather

crosses

in Fig.

impor-

I along with three

carbon tetrachloride and benzene treated as solutes

the water considered as a solute, a figure

small difference supports a point made previously a model

as

arbitrarily

the log K values

in triolein

just outside the limits of error.

(5).

differ This

(5), which is that the choice of n-octanol as

made,

was

a fortunate

one.

Another

observation,

(1,2) is the inverse relationship between octanol water partitioning and

even for such diverse compounds as halogenated compounds, aromatic and aliphaand

hydrophilic

high

water

compounds,

solubility,

although

is not

nearly

the

separation

as clear

cut

among as

the

among

latter

the

group,

hydrophobic

iiii

A few preliminary

measurements

Lindane yielded values of about phases

were

in

the

of the oleic acid-water partition coefficients

10 6 and 10 4 , respectively.

form of monolayers

enhanced partitioning.

on water

This is unlike the effect

were

for HCB and

The K values when the oleic acid

unchanged,

previously

indicating

reported

the

for octanol

lack of any monolayers

(6,7) on water.

ACKNOWLEDGEMENT

I thank J.H. Carey for supplying me with purified MTBT, and K.L.E. Kaiser for constructive criticism.

REFERENCE S

I. C.T. Chiou, V.H. Freed, D.W. Schmedding and R.L. Kohnert, Env. Sci. Techn,

ii 475 (1977).

2. M.Th.M. Tulp and O. Hutzlnger, Chemosphere, !, 849 (1978). 3. C.

Hansch

and A.

Leo,

"Substituent

Constants

for

Correlation

Analysis

in

Chemistry

and

Biology" John Wiley and Sons, New York (1979). 4. S.S. Duffey, Ann. Rev. Entomology, 25, 447 (1980). 5. R.F. Platford, Bull. Environm. Contam. Toxicol., 21, 68 (1979). 6. R.F. Platford, Chemosphere, 10, 719 (1981). 7. R.F. Platford, J.H. Carey, and E.J. Hale, Environm. Pollution B, 3, 125 (1982). 8. J.H.

Carey,

M.E.

Fox,

B.G.

Brownlee,

J.L.

Metcalfe,

P.D.

Mason

and

W.H.

submitted. 9. R.F. Platford, J. Chem. Eng. Data, submitted. I0. R.F. Platford, Envlronm. Sci. and Technol., 4, 410 (1970). II. R. Collander, Acta. Chem. Seand., ~, 774 (1951). 12. G. Lepetit, Pharmazie, 32, 289 (1977). 13. P.C. Hirom, R.D. Hughes and P. Mllburn, Biochem. Soc. Trans. 2 327 (1974).

(Received

in U K

iO J u n e

1983)

Yerex,

to

be