Hydrogen bond increments

The justihcation for this plot lies in the fact that, of the three solubility parameter increments, the dispersion parameter varies the least and, via this average way, it can be treated together with the polar increment. The hydrogen bonding increment is very important and it is thus accounted for separately in Eqnation 16.35. 

Following Bozzelli and Ritter (Lay et al., 1995 Ritter and Bozzelli, 1991), the thermochemistry of free radicals is estimated by adding Hydrogen Bond Increments (HBI) to the energy of the corresponding stable molecule where an H has capped the radical site. The HBI groups are also stored in a functional group tree. 

C—H Bond Energies and Hydrogen Bond Increment (HBI) Values. 

A method to estimate thermochemical properties for radicals from the corresponding properties of the parent and of derivation of hydrogen bond increment (HBI) groups, is described by Lay et al. [25] and Sun and Bozzelli [133]. The method uses the bond energy (298.K) for loss of a hydrogen on the central atom for the enthalpy term, the difference between the radical and the parent for the heat capacity (Cp(T)) term and the intrinsic entropy difference for the term. 

FIGURE 1.11 Systematic optimization of structural binding and stereorecognition increments of amino acid side chain (Rsa) carbamate residue (Rso)- Dependency of separation factors on the steric bulkiness of amino acid and carbamate residues as quantified by their corresponding Taft s steric parameters Es sa Eg so- (1) ionic interaction (2) jr-jr-interaction (3) hydrogen bonding (4) steric interaction. (Reproduced from M. Lammerhofer et al., J. Sep. ScL, 29 1486 (2006). With permission.)... 

The Values of Gibbs Potential (—AG(298 K)) (kj mol-1) for Hydrogen Bonding ArOH Calculated by Equation (15.9), for Increments see Handbook [4]... 

The figures in brackets are the increments resulting from the introduction of hydroxyl or carboxyl groups, For these simply related structures it would seem that the sublimation heats are derived addi-lively. Whilst this is not generally so, there are probably many other sets of structures for which this approximation applies. Without going into further examples here, it is obvious that much can be learnt of hydrogen bond contributions from lattice energies. 

Schneider, H.J. Rudiger, V. Raevsky, O.A. The incremental description of host-guest complexes Free energy increments derived from hydrogen bonds applied to crown ethers and cryptands. Org. Chem. 1993, 58 (14), 3648-3653. 

CED is determined by calculation, using the Van Krevelen increment values (Van Krevelen, 1990). There is no apparent effect of the crosslink density on K, which seems to depend (as CED), only on the molecular scale structure (polarity, hydrogen bonding). The following results were obtained with quasi-static tensile measurements (10-3-10 4 s-1 strain rate) in a temperature range 200 K-Tg, using a bidimensional extensometer to determine E and v (from which K and G could be determined) (Verdu and Tcharkhtchi, 1996) ... 

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