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Bondi volumes

Bondi volume -> molecular surface (O van der Waals molecular surface) bond number (B) ( edge counting bond count)... [Pg.28]

Bondi developed a method based on covalent bond distances and van der Waals radii to calculate van der Waals volume [Bondi, 1964]. The volume calculated in this way is sometimes called the Bondi volume. It is obtained easily by summing appropriate volume contributions of atoms and functional groups, as proposed by Bondi note that the Bondi volume does not account for the overlaps which are possible whenever three or more atomic spheres intersect it is roughly 60 - 70 % of the -> molecular volume. [Pg.327]

Bondi volume volume descriptors ( van der Waals volume)... [Pg.69]

The van der Waals volume and area are characterizing parameters relating molecular configurations. Bondi describes group contribution methods for their calculatiou. [Pg.389]

In a reversed-phase liquid chromatography system, if the hydrogen-bonding and Coulombic forces are negligible, the retention of molecules depends upon their size, and the presence of n electrons enhances the selectivity. The molecular size, i.e. the van der Waals volume, can be calculated by hand, by Bondi s method,29 or by certain computer programs. [Pg.115]

Bondi s calculation method is simple. The van der Waals volumes are the sum of the van der Waals volumes of fragments, as given in Table 6.3. The calculated van der Waals volumes are summarized in Table 6.4. However, these volumes are different from those calculated using the MOPAC-BlogP program, even though the correlation is excellent. [Pg.115]

Table 6.3 Bondi s group contributions to the van der Waals volume of hydrocarbons... Table 6.3 Bondi s group contributions to the van der Waals volume of hydrocarbons...
Figure 6.4 Relationship of log k values measured on ODS-bonded silica gel to Bondi s van der Waals volumes. Column, Develosil ODS, 15 cm x 4.6 mm i.d. eluent, 70% aqueous acetonitrile at 30 °C. Numbers beside symbols see Table 6.4 <>, Polycyclic aromatic hydrocarbons x, alkylbenzenes O, halogenated benzenes A, alkanols and , alkanes. Figure 6.4 Relationship of log k values measured on ODS-bonded silica gel to Bondi s van der Waals volumes. Column, Develosil ODS, 15 cm x 4.6 mm i.d. eluent, 70% aqueous acetonitrile at 30 °C. Numbers beside symbols see Table 6.4 <>, Polycyclic aromatic hydrocarbons x, alkylbenzenes O, halogenated benzenes A, alkanols and , alkanes.
Figure 4.30. Molecular model for dialkyl succinic acid. The C -C distance is 1.54 A the C-C-C angles are tetrahedral, Qj- = 109.47 °. The center of the negative charge was placed at a distance of 1.25/2 = 0.625 A from Ae carboxyl carbon atom, and the positive charge at a distance of 0.7 A from the negative charge. The effective radii for the various alkyl groups were computed from the van der Waals volumes given by Bondi (1968). These are methyl, 1.75 A ethyl, 1.78 A isopropyl, 2.0 A tert-butyl, 2.2 A. These radii were used to construct the Lennard-Jones potentials between the various groups [see Eq. (4.8.46)]. Figure 4.30. Molecular model for dialkyl succinic acid. The C -C distance is 1.54 A the C-C-C angles are tetrahedral, Qj- = 109.47 °. The center of the negative charge was placed at a distance of 1.25/2 = 0.625 A from Ae carboxyl carbon atom, and the positive charge at a distance of 0.7 A from the negative charge. The effective radii for the various alkyl groups were computed from the van der Waals volumes given by Bondi (1968). These are methyl, 1.75 A ethyl, 1.78 A isopropyl, 2.0 A tert-butyl, 2.2 A. These radii were used to construct the Lennard-Jones potentials between the various groups [see Eq. (4.8.46)].
In the following years, various steric parameters have been applied to the analysis besides the Taft Es value. For instance, the Hancock corrected steric E , the Bondi molecular volume Vw, and the Verloop STERIMOL parameters have been used to rationalize various steric effects depending upon the interactions involved. At every addition of such parameters, the versatility of the approach has been expanded remarkably. The number of successful applications has been growing enormously leading to the present state of development. [Pg.121]

Figure 42. Molecular volumes of 2-nonanone and its initial Norrish II photoproducts from MNDO-optimized geometries [265a] using the method of Bondi [265b]. Figure 42. Molecular volumes of 2-nonanone and its initial Norrish II photoproducts from MNDO-optimized geometries [265a] using the method of Bondi [265b].
Molecular Volume-Kow Relationships Relationships between Kow and different volume parameters have been reported. Leo et al. [41] compare correlations with Bondi and with CPK volume for two classes of apolar molecules (1) alkanes and alkylsilanes, and (2) perhalogenated alkanes and aromatic and haloaromatic compounds. Further, these authors discuss analogous correlations for alkanols and alkylphenols. [Pg.155]

Because of the lipophilic nature of the biological membrane and the importance of size and charge distribution, the formal charge at position 7 of the 1,2,4-benzothiadiazine 1,1-dioxide systems and two other parameters, Hansch s hydrophobic 1r parameter and the van der Waals volume (as calculated by Bondi s method), are included in a structure-activity rela-... [Pg.282]

There is very little problem in calculating an acceptable measure of solute size. Simple calculations of either molecular volume or area based on either Bondi s (Bondi, 1964) or McGowan s (Abraham, 1987) methods work almost as well as those derived from molecular mechanics and quantum chemistry (Leo, 1993). When volume in cubic Angstroms is used, V is normally scaled by 0.01 to produce a coefficient comparable to the others in the equation polarity/polarizability. [Pg.112]

A quite different approach to the molecular size of solvents is the estimation of its molecular surface area and volume from the van der Waals radii of the constituent atoms and the manner and geometry of their mutual bonding (Bondi 1964). The necessary calculations are quite involved, and the values shown in Table 3.4 have been taken from a single source (DIPPR 1997), in order to be consistent. The reported molar van der Waals surface areas, Ayiw, are in 104 m2 mol 1 and the molar van der Waals volumes, Fvdw, are in cm3 mol 1, the latter in order to be comparable with the molar volumes (in Table 3.1) and the intrinsic volumes, defined below, also reported in Table 3.4. [Pg.141]

Table 2.2 Calculated fractional free volume for representative membrane materials at ambient temperatures (Bondi method)... Table 2.2 Calculated fractional free volume for representative membrane materials at ambient temperatures (Bondi method)...
Figure 2.24 Correlation of the oxygen permeability coefficient for a family of related polysulfones with inverse fractional free volume (calculated using the Bondi method) [33]. Reprinted with permission from C.L. Aitken, W.J. Koros and D.R. Paul, Effect of Structural Symmetry on Gas Transport Properties of Polysulfones, Macromolecules 25, 3424. Copyright 1992, American Chemical Society... Figure 2.24 Correlation of the oxygen permeability coefficient for a family of related polysulfones with inverse fractional free volume (calculated using the Bondi method) [33]. Reprinted with permission from C.L. Aitken, W.J. Koros and D.R. Paul, Effect of Structural Symmetry on Gas Transport Properties of Polysulfones, Macromolecules 25, 3424. Copyright 1992, American Chemical Society...
In practice, the values of Vj were set equal to the volumes of the atoms in l3, as given by Bondi (1964), divided by 30. A further consideration in... [Pg.139]

The concept of free volume varies on how it is defined and used, but is generally acknowledged to be related to the degree of thermal expansion of the molecules. When liquids with different free volumes are mixed, that difference contributes to the excess functions (Prausnitz et al., 1986). The definition of free volume used by Bondi (1968) is the difference between the hard sphere or hard core volume of the molecule (Vw= van der Waals volume) and the molar volume, V ... [Pg.96]

Aroma compound Molecular weight (g/mol) Experimental van der Waals molar volume molar volume 25 °C (Bondi, 1968) (mL/mol) (mL/mol) Saturated Vapor Pressure 25 °C (Pa) Structure... [Pg.101]

The definition of the cavity (shape and size) is an intricate and delicate question that may have a considerable influence on the results (even qualitatively). In the original Onsager s theory, the molecular cavity was defined as a sphere and the volume was taken equal to the partial molecular volume of the solute in the solution. In practice, this volume can be assumed to be equal to the average volume in the pure liquid. Experimental values are then easily deduced from the experimental density of the liquid at 20°C when this quantity is available. Obviously, in SCRF applications, it became rapidly necessary to achieve a theoretical definition of the cavity applicable to any molecular structure. In former works carried out by our group [28,62], it was shown that a simple linear relationship exists between the experimental volume derived from the liquid density (Onsager s recipe) and the van der Waals volume, i.e., the volume enclosed by a set of overlapping atomic spheres with Bondi radii [63], Roughly, this relationship is... [Pg.27]

This equation provides a way to estimate the molecular cavity volume for any system but the shape of the cavity has also to be defined. Constant coordinate cavities such as the sphere or the ellipsoid are obviously not appropriate for most systems and they have been almost definitively abandoned in favor of molecular-shaped cavities. The majority of current continuum methods, and MPE as well, use van der Waals-type molecular surfaces. Atomic radii are in general larger than standard Bondi radii so that the obtained surface is close to the so-called solvent-excluding surface [64,65], Consistent with the expression for the volume given above, the order of magnitude of atomic radii should be... [Pg.28]

On the other hand, the volume contribution of structural groups already contains inbuilt information on the influence of the atomic surroundings. As a consequence the Van der Waals volume of the structural units can approximately be calculated as the sum of the Van der Waals volumes of the composing structural groups. Bondi (1964,1968) was the first to calculate the contributions of about 60 structural groups to Vw. Later Slonimskii et al. (1970) and Askadskii (1987) calculated about 100 values of atomic increments in different surroundings. Since the two approaches used the same method of calculation, and nearly equal basic data on the atomic radii, the calculated values for the structural units are approximately equal. In Table 4.2 also the group increments of Vw are shown, next to those of M. By means of these data the Van der Waals volumes of the Structural Units are easily calculated. [Pg.73]


See other pages where Bondi volumes is mentioned: [Pg.251]    [Pg.16]    [Pg.50]    [Pg.35]    [Pg.116]    [Pg.120]    [Pg.125]    [Pg.21]    [Pg.756]    [Pg.102]    [Pg.113]    [Pg.251]    [Pg.35]    [Pg.131]    [Pg.371]    [Pg.373]    [Pg.56]    [Pg.58]    [Pg.62]    [Pg.281]    [Pg.512]    [Pg.582]    [Pg.164]    [Pg.426]    [Pg.139]   
See also in sourсe #XX -- [ Pg.1193 ]




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