Water secondary, free energy’ change

The water of hydration irih and of solution are analogous and almost equal to the primary rrii and secondary moisture contents, respectively (Figure 30). Equations for the free energy changes associated with the water of hydration and of solution, in analogy with Equation 32 are given by... 

By relating the free energy change to that produced by forcibly displacing water (called secondary drainage) to that produced by forcibly displacing oil (called forced imbibition) into the same porous media, a measure of... 

Proton NMR studies of N-methyl formamide (NMF) and NMA at high dilution in deuterated solvents have shown that the level of cis isomer of NMF is 8% in water, 10.3% in chloroform, 8.8% in benzene, and 9.2% in cyclohexane, while the level of cis-NMA (a model for the secondary peptide bond) is 1.5% in water and does not change very much in nonpolar solvents [18]. Ab initio molecular calculations suggest that the small difference in dipole moments in cis and trans forms explain the relative insensitivity of amides to solvent change, unlike esters [22,41], This may be explained by nearly identical free energies of solvation for the two isomers [18]. The energy difference between cis and trans isomers in aqueous solution (AG° = 2.5 kcal mol-1) accounts for the preferential trans conformation adopted by most peptide bonds. Similar results were obtained with nonproline tertiary amides [22]. 

As briefly discussed earlier, a widely accepted mechanism for antifoaming action is that first the oil drop enters the air/water interface, and in a secondary step, begins to spread over the foam film, so causing rupture. An entering coefficient ( ) and a spreading coefficient (S) have been defined in terms of the change in free energy when the oil droplet enters the interface or spreads at the surface. These are defined as follows ... 

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