And octanol dissolve to water and water dissolve t octanol, so some chemical that have surfactant nature, the experimental value of logP is not accurate. There are many free or commercial software that calculate logP from chemical structure. But almost all program did not open the scheme and factors. I build functional group base neural network to predict logP and put it on pirika site.
I used compounds' experimental logP data and the result is like below. The area logP is large, the accuracy is very high. In that area, emulsion happen and hard to separate. I always wonder why I can estimate logP with this simple group additivity method. There was very beautiful correlation for hydro carbon compounds. So, I checked other compounds. If there are several haloganeted atoms in the molecule, logP is also determined by only Volume.
Br or I have very large volume, though if I plot them with volume, the line is same with hydrocarbon's line. The F atoms are thought to be hydrophobic nature, even though logP is governed by molecular volume. If I polt oxygen containing molecule such as alcohol, ether, ketone and aldehyd, the line is above hydrocarbon line, but it is parallel.
I've thought alcohol compounds are easily dissolve water so logP become lower value, but it is not like that. As the result, the ratio become same to other oxygen containing molecules. If inhaled or ingested, it will tend to accumulate in areas of the body that have a lot of blood flow and a lot of fat. In general, chemicals with a high pKow tend to bioaccumulate or biocentrate in organisms within the environment. That is, they concentrate in the tissues of animals -as you go up the food chain.
DDT was a prime example of this in the case of the Bald Eagle. Since we are at the top of the food chain this could also be problematic for us.
Finally, chemicals with high pKow tend to be absorbed by the skin much more readily that those with low pKow. Look at the following equation for dermal adsorption from Dr. Of course, the higher the pKow, the lower the water solubility and this is an important considerations in some exposure assessments. One can get faked out with this fact which will be the subject of my next blog and how I received what was perhaps my greatest surprise ever to date in doing an exposure assessment.
Anonymous November 12, at PM. Pragnesh Panchamvedi November 25, at AM. Anonymous July 17, at PM. The model was found to be highly useful for predicting the pH dependence within the range of pH 3 to 9. Effects of pH on the water solubility and 1-octanol-water partition coefficient of 2,4,6-tribromophenol. T1 - Effects of pH on the water solubility and 1-octanol-water partition coefficient of 2,4,6-tribromophenol. N2 - 2,4,6-Tribromophenol TBP is expected to exist in both ionic and non-ionic forms in the environment due to ionisation of the phenolic group at near neutral pH.
In this study, the water solubility Sw and 1-octanol-water partition coefficient Kow of aqueous solutions of TBP at various pH values were measured using the shake flask method. The ionisation resulted in increasing Sw and decreasing Kow by two to three orders of magnitude. Furthermore, the pH dependence of Sw and Kow was represented using a Henderson-Hasselbalch type model and the validity of the model was evaluated.
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