Log P tests

The validity of Equation (2.30) may be tested by plotting log log (p°/p) against log ( / ) (or, if more convenient, against log n) when a straight line of slope -s should be obtained for the multilayer region of the isotherm. In... 

In the case of mercaptopropionic acid, biodegradation of 96% was achieved within 28 d ia a closed botde test based oa the consumption of oxygea. The pass level of 60% was reached within 10 d of exceeding the 10% level thus, mercaptopropionic acid can be considered as readily biodegradable. It is not expected to bio accumulate, owing to the low (log P — 0.09) -octanol/water partition coefficient. 

Adiabatic calorimetry. Dewar tests are carried out at atmospheric and elevated pressure. Sealed ampoules, Dewars with mixing, isothermal calorimeters, etc. can be used. Temperature and pressure are measured as a function of time. From these data rates of temperature and pressure rises as well as the adiabatic temperature ri.se may be determined. If the log p versus UT graph is a straight line, this is likely to be the vapour pressure. If the graph is curved, decomposition reactions should be considered. Typical temperature-time curves obtained from Dewar flask experiments are shown in Fig. 5.4-60. The adiabatic induction time can be evaluated as a function of the initial temperature and as a function of the temperature at which the induction time, tmi, exceeds a specified value. 

As in isocratic mode, the estimate of log P is indirect and based on the construction of a linear retention model between a retention property characteristic of the solute (logkw) and a training set with known logP ci values. To assess the most performing procedures, the three hydrophobicity indexes (( )o, CHI and logkw) were compared on the basis of the solvation equation [41]. These parameters were significantly inter-related with each other, but not identical. Each parameter was related to log P with values between 0.76 and 0.88 for the 55 tested compounds fitting quality associated with the compound nature. 

We want to thank Alex Avdeef for supply with an updated log P database. Thanks are also due to Pranas Japertas (Pharma Algorithms, Canada) for calculating the test set with AB/LogP and to Remy Hoffmann (Accelrys, Prance) for doing such calculations with ALOGP98. 

Physicochemical and biological parameters obtained from 6 oxazepine (X = O) and 6 thiazepine (X = S) neuroleptics. These include Hammett s electronic parameter (o ), lipophilicity (log P) and its squared value, and the activities (log l/EDjn) in two pharmacological tests in rats [41]. 

Here we assume that the daystodeath variable is the number of days to death or last known date alive for the patient. The deathcensor variable value is 1 if the patient died and 0 if the patient did not die. The p-value variable for the log-rank test is called ProbChiSq in the pvalue data set where the Test variable equals Log-Rank. ... 

AtCCD7 (Schwartz et al. 2004). Organic solvent addition (dioxane, DMSO, methanol or acetone) improved activity under low concentrations (Mathieu et al. 2007). Short chain aliphatic alcohols activated the enzymes although the reason for this activation is unclear (probably due to influences on substrate accessibility or micellar structure). An increase in activity was observed for all aliphatic alcohols tested, although the optimal concentration lessened with increasing log P values (Schilling etal. 2007). 

The logarithm for the capacity factor correlates well with known log P values obtained by the shake flask method. In practice, the k values are determined isocratically from 70 to 30% organic mobile phase and then extrapolated to 0%. Prior to determining the log P for an unknown compound, a set of structurally related molecules (standards) are analyzed to construct a correlation model between the logarithm of the retention factor and known log P values. The process is then repeated for the test compounds and their log P values determined from the mathematical relationship established for the standard compounds. 

As the logarithm of 1-octanol-water partition coefficient (log P) describes the hydrophobicity of molecules and the retention of solutes in RP-HPLC depends on the hydrophobicity, a strong correlation can be expected between the log V value and the retention of solutes in RP-HPLC. Besides log P, a considerable number of physicochemical parameters have been tested for their capacity to predict retention in RP-HPLC. Thus, Snyder s polarity index, fraction of positively and negatively charged surface area, molecular bulkiness, nonpolar surface area, electron donor and acceptor capacity, various ster-ical parameters, and the energy of highest occupied molecular orbit have all been included in QSRR calculations. 

---