Enthalpic gain

Equation 16 indicates that, even if one changes the cation, ligand, solvent, or any other perturbing factor(s) in order to stabilize a cation-ligand complex, the enthalpic gain thus obtained (AAH) is not fully reflected to the complex stability but is canceled in part (1 - a) by the entropic loss (AAA). Hence, the slope of AH-TAS plot is taken as a quantitative measure of the entropic loss upon complex formation. 

With the above simple examples we wish to emphasize that the synthetic use of hydrogen bonding assemblies in the effective formation of supramolecular macrocycles relies on high EM values and on the establishment of stable intermolecular arrays of hydrogen bonds capable of affording a high enthalpic gain to compensate for the entropic cost of the assembly. 

In chloroform, the authors estimated an enthalpic gain upon formation of such a hydrogen-bonded network of ca. 24kcalmol1 (1.3kcalmol 1 for each hydrogen bond).1) However, formation of a cydic aggregate by interaction of six molecules... 

Adamantane (47), however, only offers weak van der Waals interactions to the inner concave surface of the host assembly. This interaction, together with the enthalpic gains provided by the formation of 16 hydrogen bonds, is enough to overcome the entropy penalty for bringing together four monomers and one guest. 

Positive enthalpy and entropy terms were calculated meaning that, contrary to self-organisation processes in apolar solvents, the enthalpic gain and entropic cost are completely overriden by solvation effects. Attempted inclusion of even small diatomic guests leads to a widening and thus a destabilisation of the cap-... 

Su et al. have undertaken a detailed examination of the mechanism by which perfluoroalkyl end-groups enrich the surfaces of blends of homopolymers with their end-group fluorinated equivalents 43. Their studies aimed to assess the parameters involved in determining whether the enthalpic gain from fluorine surface enrichment outweighed the entropic penalty of polymer chains having... 

More recently, a systematic study of the properties of side-chain LC dendrimers has been undertaken on these PPI dendrimers and also on PAMAM systems by Serrano et al. [211]. In these dendrimers, the mesogenic group is connected to the dendritic scaffold by an imine linkage. In all cases, it was found that the enthalpic gain of the mesogenic units arranged as in a classical liquid crystalline mesophase dominates over the entropic tendency of the dendrimer core to adopt a globular isotropic conformation. The flexibility of the dendritic PAMAM and PPI cores allows the macromolecule to adopt... 

Very few reactions of silanones have been proposed. Left to its own devices, H2Si = O will dimerize with no calculated barrier and an enthalpic gain of 106 kcal/mol. The dimer is also subject to facile insertion by silanone, and thus the observation of D3 and D4 products is often cited as evidence for silanone intermediacy. 

---