The octanol–water partition coefficient, P, is a widely used parameter for correlating biological effects of organic substances. It is a property of the two-phase system in which water and 1-octanol are in equilibrium at a fixed temperature and the substance is distributed between the water-rich and octanol-rich phases. P is defined as the ratio of the equilibrium concentration of the substance in the octanol-rich phase to that in the water-rich phase, in the limit of zero concentration. In general, P tends to be large for compounds with extended nonpolar structures (such as long chain or multi-ring hydrocarbons) and small for compounds with highly polar groups. Thus P (or, in its more common form of expression, log P) provides a measure of the lipophilic vs. hydrophilic nature of a compound, which is an important consideration in assessing the potential toxicity. A discussion of methods of measurement and accuracy considerations for log P may be found in Ref. 1.
This table gives selected values of log P for about 450 organic compounds, including many of environmental importance. All values refer to a nominal temperature of 25 °C. The references contain data on many more compounds than are included here.
Column definitions are as follows.
Column heading | Definition |
Name | Systematic name of compound; compounds are listed alphabetically |
Mol. form. | Molecular formula of compound |
log P | log10 of octanol-water partition coefficient |
Ref. | Reference |
Name | Synonym | Mol. form. | Formula | CAS Reg. No. | Mol. wt. | log P | Ref. |
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Acenaphthene | 1,2-Dihydroacenaphthylene | C12H10 | C12H10 | 83-32-9 | 154.207 | 3.96 | 4 |
Acetaldehyde | Ethanal | C2H4O | CH3CHO | 75-07-0 | 44.052 | 0.45 | 1 |
Acetamide | Ethanamide | C2H5NO | CH3CONH2 | 60-35-5 | 59.067 | -1.26 | 1 |
Acetic acid | Ethanoic acid | C2H4O2 | CH3COOH | 64-19-7 | 60.052 | -0.17 | 1 |
Acetone | 2-Propanone | C3H6O | (CH3)2CO | 67-64-1 | 58.079 | -0.24 | 1 |
Acetonitrile | Methyl cyanide | C2H3N | CH3CN | 75-05-8 | 41.052 | -0.34 | 1 |
Acetophenone | Methyl phenyl ketone | C8H8O | C6H5C=OCH3 | 98-86-2 | 120.149 | 1.63 | 1 |
Acridine | Dibenzo[b,e]pyridine | C13H9N | 260-94-6 | 179.217 | 3.40 | 1 | |
Acrolein | 2-Propenal | C3H4O | CH2=CHCHO | 107-02-8 | 56.063 | -0.01 | 1 |
Acrylamide | 2-Propenamide | C3H5NO | C3H5NO | 79-06-1 | 71.078 | -0.78 | 1 |
Acrylonitrile | Propenenitrile | C3H3N | CH2=CHCN | 107-13-1 | 53.063 | 0.25 | 1 |
Allyl alcohol | 2-Propen-1-ol | C3H6O | C3H6O | 107-18-6 | 58.079 | 0.17 | 1 |
Allylamine | 2-Propen-1-amine | C3H7N | CH2=CHCH2NH2 | 107-11-9 | 57.095 | 0.03 | 1 |
Aniline | Benzenamine | C6H7N | C6H5NH2 | 62-53-3 | 93.127 | 0.90 | 1 |
Anisole | Methoxybenzene | C7H8O | C7H8O | 100-66-3 | 108.138 | 2.11 | 1 |
Anthracene | C14H10 | C14H10 | 120-12-7 | 178.229 | 4.56 | 4 | |
trans-Azobenzene | trans-Diphenyldiazene | C12H10N2 | 17082-12-1 | 182.220 | 3.82 | 1 | |
Azulene | Bicyclo[5.3.0]decapentaene | C10H8 | C10H8 | 275-51-4 | 128.171 | 3.22 | 1 |
Benzaldehyde | Benzenecarboxaldehyde | C7H6O | C6H5CHO | 100-52-7 | 106.122 | 1.48 | 1 |