I-Octanol

The HYBOT descriptors were successfully applied to the prediction of the partition coefficient log P (>i--octanol/water) for small organic componnds with one acceptor group from their calculated polarizabilities and the free energy acceptor factor C, as well as properties like solubility log S, the permeability of drugs (Caco-2, human skin), and for the modeling of biological activities. 

Distribution of benzodiazepines in I-octanol - water system was investigated by a direct shake flask method at the presence of the compounds used in HPLC mobile phases the phosphate buffer with pH 6,87 (substances (I) - (II)), acetic and phosphate buffer, perchloric acid at pH 3 (substances (III) - (VI)). Concentrations of substances in an aqueous phase after distribution controlled by HPLC (chromatograph Hewlett Packard, column Nucleosil 100-5 C, mobile phase acetonitrile - phosphate buffer solution with pH 2,5, 30 70 (v/v)). 

In the recent past separation of isomers has been attempted using aqueous liquid membranes based on p-cyclodextrin. Thus, separation of a mixture of o- and p-nitroaniline (in 80% i-octanol, 20% -heptane) has been studied, with the p-isomer showing a selectivity of 5 at 0.7 molar p-cyclodextrin. Even stereoisomers of stilbene cis and trans) were separated using a 0.02 to 0.2 M cyclodextrin solution, but the selectivity was less than 2 (Mandal et al, 1998). 

Kawamoto, K. and Urano, K. Parameters for predicting fate of organochlorine pesticides in the environment (I) octanol-water and air-water partition coefficients, Chemosphere, 18(9/10) 1987-1996, 1989. 

Fio. 38. Plot of the algorithm of the retention factor, k, and log P, the water-/i>octanol partition coefficient of eight amino acids. The chromatographic data were obtained on 3 ftm LiChrosorb kP-8, 230 x 4.6 mm i.d. eluierit 0.1 M aqueous phosphate buffer, pH 6.7, T 70 C. Eluites Trp, tryptophan Phe, phenylalanine Leu, leudne Val. valine Tyr, tyrosine Lys, lysine Ala, alanine Gly, glycine. Reprinted with permission from Molnar and Horvith QOS). 

Die optische Ausbeute erreicht im ersten Falle Werte bis 55,7 %. Fiir die zweite Reaktion leiten die Autoren die absolute Konfiguration des End-produktes aus der der eingesetzten HiIfsalkohole (i )(—)-Octanol-(2) und (i ) —)-Menthol mit Hilfe des oben formulierten Prelog -Modells und weiterer mechanistischer Uberlegungen her. 

Because the physicochemical basis of chromatographic retention on hydrocarbonacous stationary phases with aqueous eluents and the liquid-liquid partition of solutes between nonpolar organic solvents, e.g., /i-octanol, and aqueous solvents are similar, selectivities can be expressed in terms of partition coefficients by the relationship... 

With this representation in mind, a partial explanation can bc presented as to why the /i-octanol/water partitioning system seems to mimic the lipid mcmbranc.s/watcr sy.stctns found in the body. It turns nut that /i-octanol is not as nonpolar as initially might be predicted. Water-saturated octanol contains 2..1 M water because the small water molecule easily clusters around oclunoTs hydroxy moiety. -Ocianol-satur-ated water contains little of the organic phase bccau.se of the large hydrophobic 8-carbon chain of octanol. The water in the /t-octanol phase apparently approximates the polar prop-... 

Drug paniiioning. 18-21. I9f /i-octanol/watcr system and. 19-20 partition coefficient and, 19-21 Drug-reccpior interactions. 3, 8-9. 27-.3.5 activc sitc-dircctcd irreversible inhibition in. 29... 

Note. (1) Initial composicions feed (a) equimolar 0.005 M solution of o- NA and p-NA in 80% I-octanol and 20% heptane, and(b) equimolarO.Ol M solution of and frart5-stilbene in pure heptane strip (i) 80% I-octanoland20% heptane and (b) pure heptane. Membrane Celgard X-10 microporous hollow fibers. (2) Sour[Pg.319]

Silica/i-Octanol. The monomer and excimer fluorescence decays of 1Py(3)1Py in the system silica/octanol were fitted with three exponentials (38), double-exponential fits giving unacceptable results. The decay times at 25°C (38) for the monomer (20, 43 and 146 ns), have values in the same range as those of the excimer (27, 51 and 106 ns). As was noted in studies with 1Py(3)1Py and related compounds in homogeneous solution (20,62), the monomer decay often contains a contribution from an impurity with a lifetime similar to that of e.g. 1-methylpyrene (x ), becoming more important with increasing fluorescence quenching. This then leads to the difference observed in the longest decay times of excimer and monomer. 

Table 8.1. Observed second-order rate coefficients for aldol condensation of n-butanal (11 %wt in /i-octanol, potassium-octoate buffer, 171 °C) [16].

ATow.i Octanol-water partition coefficient of species i Kc Concentration-based partition coefficient of species i Kx Mole fraction-based partition coefficient of species i r Lower consolute or lower critical solution temperature (K) Upper consolute or upper critical solution temperature (K) X Set of liquid-phase mole fractions X, X2,. n Osmotic pressure (kPa)... 

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