The determination of air/water partition coefficients for alkyl carboxylic acids by a new indirect method

Abstract

The air/water partition coefficients of carboxylic acids, Kw, especially those of high molecular weight, are very difficult to determine directly. Values of Kw can be obtained by an indirect method as Kw = K/P where K is an air/solvent partition coefficient and P is the corresponding water/solvent partition coefficient. In the present method, gas-liquid chromatographic data and water/solvent partition data are used to obtain 'descriptors' of carboxylic acids that can then be used to determine the required K, P, and thus Kw values. These are reported for all the 24 n-alkyl carboxylic acids from formic acid to n-tetracosanoic acid, and for seven branched chain alkyl carboxylic acids. There is good agreement with literature values of Kw, where available, although the present data on the n-alkyl carboxylic acids is much more self consistent than the literature data.

Modeling Free Energies of Solvation in Olive Oil

“…The SM8 descriptors φ and ψ were set to zero since olive oil is primarily composed of triglycerides and fatty acids having neither halogens nor aromatic carbon atoms. Given these major components of olive oil, we set β equal to 0.45, which is characteristic of both types of compounds 76,94–96. The α descriptor, however, cannot be as easily defined, since for long chain esters a value of 0.00 is appropriate,76,94,95 while for fatty acids a value of 0.60 would be expected 76,96.…”

“…Given these major components of olive oil, we set β equal to 0.45, which is characteristic of both types of compounds 76,94–96. The α descriptor, however, cannot be as easily defined, since for long chain esters a value of 0.00 is appropriate,76,94,95 while for fatty acids a value of 0.60 would be expected 76,96. If a weighted value of α were to be assigned based upon composition, it would be ~0.01, which is insignificant; however, our investigation, as well as that of Abraham and Ibrahim,45 suggests that olive oil does exhibit significant hydrogen bond acidity.…”

Linear Free Energy Relationship Analysis of Retention Factors in Cerasome Electrokinetic Chromatography Intended for Predicting Drug Skin Permeation

“…SP represents a set of solute properties in a given system, for example, SP could be the n ‐octanol–water distribution coefficient log D oct , the skin permeability log K p , or the retention factor log k in LEKC for a series of solutes. Equation 1 has been successfully tested in a wide range of systems, including a large number of partitions from water to organic solvent,12,14,15 various artificial membrane models,9,13,16 as well as biological processes 17–19. The coefficients in Eq.…”

“…In the present study, all the measurements were performed at pH 7.4, where some of the solutes summarized in Table 1 are present as ionic species: cations from protonated amines and anions from deprotonated carboxylic acids. Equation 1 was set up for neutral solutes only12–19 and to extend it to ionic species Abraham and Acree20–23 developed Eq. 2.…”

The hydrogen bond acidity and other descriptors for oximes

“…[13][14][15][16] In brief, equations on the lines of eqn (5) Cyclohexanone oxime and acetone oxime are solids, but a number of lower oximes are liquids whose refractive index has been measured, 19 and for which we have calculated E, see Table 3. Also included are values of E calculated from the ACD refractive index, 18 and values of E calculated through the PharmaAlgorithm (PHA) program.…”