Calculation of hydrophobic constant (log P) from .pi. and f constants

Abstract

The highest level of confidence can be placed in calculated log P values when (1) the log P of a parent solute is known, (2) pi constants for the required substituent(s) are available, and (3) the substituents either do not have an effect on groups already present in the parent or else this effect has been previously determined. In some instances there are no values available for any related structures which could serve as a parent; then, rather than substitute groups for hydrogen, it is easier to begin "from scratch", as suggested by Nys and Rekker, and assemble the structure from fragments, each of which has been assigned a hydrophobic value. In the present paper some new log P values for the lower alkanes and the inert gases are analyzed with the view of separating hydrophobic effects according to volume (including branching and flexibility) and polarity. Modified fragment values appear to enable reliable calculations to be made for a wider range of structures than was possible with the originally proposed constants.

Derivatives of 4-dihydro-4-deoxy-4(R)-amino spectinomycin and their activity against susceptible and resistant Escherichia coli strains

“…This discrepancy may be due to folding or balling of long alkyl side chains which reduces the observed lipophilicity. This observation is in agreement with other investigations (21,27,35), in which the IT value for CH2 in alkyl chains longer than 7 carbon atoms was observed to be 0.37. Therefore, for CH2 substituents in alkyl chains with more than 7 carbon atoms, r = 0.37 was employed in the calculations.…”

Antibacterial Activity Exerted by some Diazabicyclo-steroid Derivatives Against Staphylococcus Aureus and Streptococcus Pneumoniae

“…The 13 C NMR spectra showed chemical shifts at 16.12, 22.10 and 26.90 ppm for methylene groups bound to both alkyne and aldehyde groups; at 21.00, 35.54, 43.50 and 44.62 ppm for methylene groups involved in the arm bound to both aldehyde and cyclobutene ring; at 51.22-51.76 and 54.10 ppm for methylene groups bound to amino and imino groups; at 79. 60 …”

“…Theoretical results indicate that hydrogen-interaction between compound 20 and DNA gyrase (Fig. 11, 12 In order to delineate the structural chemical requirements of compounds 18, 20 and 23; other parameters such as the logP and πdescriptors were calculated, with the purpose to know if there are differences in its lipophilicity degree 60 . There are studies which indicate that logP estimates the logarithmic octanol-water partition coefficient; therefore the logPrepresents the lipophilic effects of a molecule which includes the sum of the lipophilic contributions of the parent molecule and its substituent 61 .…”

Estudo do coeficiente de partição octanol-água de bifenilas policloradas (PCBs) utilizando parâmetros topológicos

“…Neste caso, log K OW é estimado a partir da contribuição aditiva de grupos funcionais e fragmentos anexados à base molecular 12 ; (ii) métodos baseados na contribuição atômica 13 , em que cada átomo tem uma contribuição aditiva para o log K OW da molécula. No caso dos PCBs, estes métodos não produzem resultados precisos, uma vez que os valores obtidos de log K OW para PCBs de um mesmo grupo homólogo têm o mesmo valor; (iii) métodos baseados em modelos que utilizam parâmetros obtidos por meio de cálculos quânticos 14 .…”