LSER

An empirical solution of Eq. (1) consists of analysis of the solvation process of the target molecule in solute, finding descriptors, which govern each phase and using them to calculate logP. This was done, for example, in the LSER approach which considered that the process of any solvation involves (i) endoergic creation of a cavity in the solvent and (ii) incorporation of the solute in the cavity with consequent setting up of various solute-solvent interactions [4—6]. Each of these steps 

In this equation E (R2) is the excess molar refraction, S (tt ) is the solute dipolarity-polarizabiUty, A (2a ) and B(2 3 ) are the solute H-bond acidity and basicity, respectively, and Vis the McGowan characteristic volume (in cm mol /100). The solute size, V, (molecule favors octanol) together with solute H-bond basicity, B, (favors water) are the dominating parameters of this equation. The use of Bo(2P ) resulted in equation 

Another implementation of this method [8] is available in the ChemProp software developed by the group of Gerrit Schuiirman [12]. 

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LORG (localized orbital-local origin) technique for removing dependence on the coordinate system when computing NMR chemical shifts LSDA (local spin-density approximation) approximation used in more approximate DFT methods for open-shell systems LSER (linear solvent energy relationships) method for computing solvation energy... 

Linear Free Energy—Linear Solvation Energy Relationships. Linear free energy (LFER) and linear solvation energy (LSER) relationships are used to develop correlations between selected properties of similar compounds. These are fundamentally a collection of techniques whereby properties can be predicted from other properties for which linear dependency has been observed. Linear relationships include not only simple y = rax + b relationships, but also more compHcated expressions such as the Hammett equation (254) which correlates equiUbrium constants for ben2enes,... 

Kamlet-Taft Linear Solvation Energy Relationships. Most recent works on LSERs are based on a powerfiil predictive model, known as the Kamlet-Taft model (257), which has provided a framework for numerous studies into specific molecular thermodynamic properties of solvent—solute systems. This model is based on an equation having three conceptually expHcit terms (258). 

Owing to the original determination from uv—vis spectral solvatochromic shifts, 7T, B, and are called solvatochromic parameters. General rules for estimation of these variables have been proposed (258). Examples of individual parameter investigations are available (260,261). As previously mentioned, individual LEER—LSER studies are performed on related materials. A common method to link these individual studies to group contribution methods, and thereby expand the appHcabiUty, is by expansion of solvatochromic parameters to log—linear relationships, such as... 

A sampling of appHcations of Kamlet-Taft LSERs include the following. (/) The Solvatochromic Parameters for Activity Coefficient Estimation (SPACE) method for infinite dilution activity coefficients where improved predictions over UNIEAC for a database of 1879 critically evaluated experimental data points has been claimed (263). (2) Observation of inverse linear relationship between log 1-octanol—water partition coefficient and Hquid... 

As computing capabiUty has improved, the need for automated methods of determining connectivity indexes, as well as group compositions and other stmctural parameters, for existing databases of chemical species has increased in importance. New naming techniques, such as SMILES, have been proposed which can be easily translated to these indexes and parameters by computer algorithms. Discussions of the more recent work in this area are available (281,282). SMILES has been used to input Contaminant stmctures into an expert system for aquatic toxicity prediction by generating LSER parameter values (243,258). 

Univariate LSERs may possess the conventional LEER form, as exemplified by Eq. (8-67), the Grunwald-Winstein equation, or they may simply be plots of log k against a solvent parameter such as Z, (30), or ir. Brownstein developed an LEER form for the latter type of correlation, writing... 

The most familiar multivariate LSER is that of the Kamlet—Taft group, whieh in its fully rigged form is now written... 

LEKC/VEKC Hposome/vesicular electrokinetic chromatography LSER Hnear solvation energy relationship... 

The SPARC (Sparc Performs Automated Reasoning in Chemistry) approach was introduced in the 1990s by Karickhoff, Carreira, Hilal and their colleagues [16-18]. This method uses LSER [19] to estimate perturbed molecular orbitals [20] to describe quantum effects such as charge distribuhon and delocalizahon, and polarizability of molecules followed by quanhtative structure-activity relationship (QSAR) studies to correlate structure with molecular properties. SPARC describes Gibbs energy of a given process (e.g. solvation in water) as a sum of ... 

ABSOLV, LSER Pharma Algorithms, Lithuania/Canada http //www.ap-algorithms.com 2D 8,9... 

LSER UEZ" Helmholtz Centre for Environmental Research - UFZ, Germany ralph.kuehne ufz.de 2D 12... 

Our analysis included three LSER-like models. Two of them were provided by Pharma Algorithms and differed only with respect to the used regression coeffi-... 

Similar studies have been performed for a series of nitrophenols [299], showing the ability of the A log P parameter to identify the presence of intramolecular H-bonds in a series of eongeners. This is of pharmaeeutical relevance, since, as mentioned above, it is often reeognized that the A log P parameter is a good predietor of biodistribution and passive diffusion [215,300]. This approaeh is as yet restrieted to neutral speeies, because of the diflieulty in establishing LSER for ions. It would yet be of great interest to enlarge the speetrum of LSERs to this field. 

LSER linear solvation energy relationship MLP molecular lipophilicity potential n mole number N neutral species... 

In order to better investigate the relationship between sensor response and interaction mechanism it is useful to consider the way in which each volatile compound is expected to interact when in contact with a solid phase. These interactions can be modelled using the linear sorption energy relationship approach (LSER) [23]. 

LSER coefficients for various analytes are available in [23]. Figure 7 shows the values of the five parameters for the five volatile compounds considered here. 

K and A being known, the solution of equation 13 allows the determination of the LSER parameters characterizing the sensors studied here. Equation 12 was solved with the least squares method. In Figure 8 the LSER parameters for each sensor are shown. 

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