Drago four-parameter equation

Hydrogen bonding is a special type of acid-base interaction (see Chapter 9). Probably the most important equation relating hydrogen bond strengths is the equation known as the Drago four-parameter equation,... 

Table 9.7 Acid and Base Parameters for Use in the Drago Four-Parameter Equation.

Drago and co-workers have correlated a large body of enthalpies of adduct formation in Lewis acid-base systems, including some solvents as reactants, with this four-parameter equation ... 

A four-parameter equation for predicting the calorimetric enthalpies of acid-base interactions, —Ai/ab, in neutral solvents, proposed by Drago et al. [146], with spectroscopically determined shifts of the OH stretching frequency of phenol when interacting with a variety of bases of dilute solutions in carbon tetrachloride and tetrachloroethylene. 

Doan and Drago [153,154] have reported an extended work that Eq. (61) include the spectral shifts obtained from the LSERs approach. They showed that a four-parameter equation for a general set of electron donors (acceptors), in which the specific interaction or spectral shift with an electron acceptor (donors) can be fit by LSERs. 

Drago has proposed a four-parameter equation designed to predict acid-base reaction enthalpies in the gas phase or in poorly solvating media ... 

One could, of course, attempt to use Equation (1.4) by taking one set of data to assign values of 5a, 5b, [Pg.5]

Drago proposed a four-parameter equation to predict the heat of add base adduct formation [31] ... 

Drago s concept has the merit that two specific factors governing the solvent effect are written together in one common equation. As seen above, characterization of the solvent effect by means of this model succeeded well in certain systems, and less well in others. It appeared that replacement of the two-parameter approach by several parameters might lead to a more generally valid solution. For a joint description of non-specific and specific effects, Koppel and Palm [Ko 72] proposed the introduction of the following four-parameter equation ... 

Similar to the perturbation theory, Drago and Wayland proposed a four-parameter equation for predicting reaction enthalpies between acid and base species (Drago and Wayland 1965). Both species are each characterized by two independent parameters an E value which measures their ability to partidpate in electrostatic bonding, and a C value which measures their ability to participate in covalent bonding, leading to ... 

Drago, R.S., Vogel, G.C. and Needham, T.E. (1971) Four-parameter equation for predicting... 

The double-scale four-parameter enthalpic equation proposed in 1965 (54) and successfully developed by Drago et al seems to be the best tool so far available for correlating and predicting the formation enthalpies of Lewis adducts in the gas phase or, if really necessary, in solution. 

Even if Drago s concept is an attempt to circumvent the quantum mechanical consideration of bond formation, the major importance of the above four parameters is their relationship with the HSAB principle. Actually, through the plot of Ea versus Ca for several liquids on a solid one can obtain indirectly the values of the chemical softness I/77 from the slope of C/E, as represented by the following equation ... 

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