Hydrophobicity Parameters Determined by Reversed-Phase Liquid Chromatography. X. Relationship between Capacity Factor and Octanol-Water Partition Coefficients of Monosubstituted Thiophenes.

Hydrophobicity Parameters Determined by Reversed-Phase Liquid Chromatography. XV: Optimal Conditions for Prediction of log Poct by Using RP-HPLC Procedures.

“…[10][11][12][13][14][15] One explanation for these phenomena could be that residual silanols which act as H-donors would interact with H-accepting solutes via H-bondings. To explore this possibility, we attempted to examine the influence of residual silanols by comparing log k values for the same compounds measured on the C18-UG column with the previous data obtained on the SG-column.…”

“…3,5,8) In our experience, this log k W approach works well for non-polar solutes but tends to provide overestimated log P oct values for strong H-acceptors. [10][11][12][13][14][15] From systematic studies of log k obtained under various HPLC conditions for typical heteroaromatic compounds such as (di)azines, furans and thiophenes, we were led to the conclusion that the use of an eluent containing around 50% methanol, which usually provides a more direct correlation with log P oct , is the most convenient and practical procedure for rapid estimation of log P oct provided H-donors (amphiprotic compounds) are treated separately.11-15) Our results so far obtained are illustrated graphically in Fig. 1.…”

Hydrophobicity as a Key Physicochemical Parameter of Environmental Toxicology of Pesticides

“…For those having amphiprotic substituents, the situation is less straightforward, requiring additional parameters (Fujita et al, 1977). and Yamagami et al (1990Yamagami et al ( , 1994 have further indicated that the correlation of the type of Eq. 3 should generally be dealt with so as to include, besides the previously mentioned indicator variable terms, parameter terms representing mutual electronic effects among substituents or functional groups in a number of substituted heteroaromatic compound series.…”

Measurement and prediction of hydrophobicity parameters for highly lipophilic compounds: Application of the HPLC column-switching technique to measurement of log P of diarylpyrazines

“…[13][14][15]18,19 It is very often observed that hydrogen bonding effects of solutes with the surrounding molecules break a linearity, making the HPLC approach less effective for the estimate of log P. In an attempt to establish a standard HPLC procedure for predicting reliable log P values, we have studied the relationship between log P and log k for various series of fundamental heteroaromatic compounds, such as monosubstituted pyridines, diazines, and thiophenes, under various HPLC conditions. [13][14][15]20 Our results have demonstrated that hydrogen donating solutes (amphiprotics) usually behave differently from nonamphiprotics and should be treated separately. [13][14][15] Moreover, the log k W method tends to overestimate log P for strong hydrogen acceptors.…”

“…For this reason, most of pyridines and diazines which have N-atom(s), a strong hydrogen acceptor, in the parent rings have been found to yield values for log k W much higher than that corresponding to the true value for log P. Instead, we have found that isocratic log k obtained with an eluent containing around 50% methanol usually results in a good linear relationship with log P, permitting us to reliably predict values for log P over the range, -1 < log P < 3. [13][14][15]20 Even when such empirical predictive methods are known to be reliable, accurate experimental values of log P for several compounds are required.…”