Reflection coefficient alcohols

Table 3-3. Reflection Coefficients of Chloroplastsfrom Pisum sativum far Alcohols Varying in C content.3...

Wang, C.-t., and Nobel, P.S. 1971. Permeability of pea chloroplasts to alcohols and aldoses as measured by reflection coefficients. Biochim. Biophys. Acta 241 200-212. 

These equations show that hydrophobic and steric (van der Waals) interactions are of prime importance in the inclusion processes of cyclodextrin-alcohol systems. The coefficient of Es was positive in sign for an a-cyclodextrin system and negative for a P-cyclodextrin system. These clear-cut differences in sign reflect the fact that a bulky alcohol is subject to van der Waals repulsion by the a-cyclodextrin cavity and to van der Waals attraction by the p-cyclodextrin cavity. 

In 1868 two Scottish scientists, Crum Brown and Fraser [4] recognized that a relation exists between the physiological action of a substance and its chemical composition and constitution. That recognition was in effect the birth of the science that has come to be known as quantitative structure-activity relationship (QSAR) studies a QSAR is a mathematical equation that relates a biological or other property to structural and/or physicochemical properties of a series of (usually) related compounds. Shortly afterwards, Richardson [5] showed that the narcotic effect of primary aliphatic alcohols varied with their molecular weight, and in 1893 Richet [6] observed that the toxicities of a variety of simple polar chemicals such as alcohols, ethers, and ketones were inversely correlated with their aqueous solubilities. Probably the best known of the very early work in the field was that of Overton [7] and Meyer [8], who found that the narcotic effect of simple chemicals increased with their oil-water partition coefficient and postulated that this reflected the partitioning of a chemical between the aqueous exobiophase and a lipophilic receptor. This, as it turned out, was most prescient, for about 70% of published QSARs contain a term relating to partition coefficient [9]. 

In the absence of alcohol the salinity/alkane sensitivity will be dominated by the nature of the surfactant hydrophile. A linear response was observed between optimal salinity and alkane chain length for the ICI NP6 surfactant with a recorded coefficient of ds /d EACN = 17.Sgdm "3/1 EACN. This high salt tolerance was expected for nonionics and can reflect an... 

Phthalocyanine-based dyes are especially useful for CD-R, as the chromophore absorption band falls in the desirable spectral range, and they are noted for excellent photostability. Unlike cyanine dyes, phthalocyanines tend to have very poor solubility, particularly in solvents such as alcohols and aliphatic hydrocarbons (which do not attack polycarbonate and are therefore used for spin coating). Therefore, the main barrier to the wider use of these dyes is the relatively high cost of synthesizing soluble derivatives. Suitable modifications to the Pc core which have been developed, notably by Mitsui Toatsu, are shown in Scheme 7. The bulky R groups reduce undesirable molecular association (which in turn lower the extinction coefficient and hence reflectivity), whereas partial bromination allows fine-tuning of the film absorbance and reflectivity. The metal atom influences the position of the absorption band, the photostability, and the efficiency of the radiationless transition from the excited state.199 This material is marketed by Ciba as Supergreen.204... 

It has been observed that the rate of the base-catalyzed hydrolysis of esters of phtha-lic acid decrease with the size of the alcohol moiety, Table 8.2. A Taft-Hancock relation relates rate constant, k, to the inductive effect of these substituents cr, the steric effect and the rate constant feo of the dimethyl ester. The coefficient 4.59 corresponds to the p of the Hammett equation and reflects the sensitivity to... 

The transport properties, flux and selectivity, can be correlated with two thennodynamic parameters, i) sorption and ii) preferential sorption (see also chapter V). The sorption value reflects the overall interaction of the liquid mixture towards the membrane material. Figure VI - 24 shows the sorption value (left) and the flux (right) of a mixture of toluene-ethanol in a membrane consisting of a blend of polyvinyl alcohol (PVA)-poly acrylic acid (PAA) [41]. It can be seen that with increasing alcohol concentration in the liquid mixture the overall sorption value increases. The transport resistance in this swollen network will decrease and consequently the flux (or better the permeability coefficient) will increase. In fact both the diffusivity (due to increased swelling) and the solubility (due to increased interaction) increase. 

The AG value deduced from the PMF is corrected by replacing classical vibrational partition functions by their quantum homolog. Recrossing, tunnelling and non-classical reflection effects can be included in the transmission coefficient by various procedures. This ensemble-average variational transition state theory with multidimensional tunnelling (EA-VTST/MT) method was applied to proton and hydride transfers in various enzymes such as yeast enolase, liver alcohol dehydrogenase and triosephosphate isomerase. For a review, see ref. 3 and the chapter by J. Gao in this book. 

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