Drago equation parameters

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.

Jensen [9] indicated that there is no evidence that Drago s parameters reflect the relative electrostatic and covalent contributions to the bonding in resulting adducts. They were not correlated with either a physical property (dipole moment, ionization potential) or with a quantum-mechanically calculated index. Drago s approach is a purely empirical method of calculating enthalpy of formation for molecular adducts. Fowkes applied the Lewis E C equation [19] and has attempted to determine E and C parameters for both polymers and surfaces. However, Jensen [9] indicated the potential problem connected... 

However, the sequence of C/E values is not in accordance with practical experience with the solvents. Drago s parameters and his equation also could not be used to describe Pearson s hard-soft concept. 

An alternative set of factors to HSAB theory that takes into account both electrostatic and covalent contributions is the Drago-Wayland parameters. The enthalpy of formation for the generic acid-base reaction in Equation (14.18) can be calculated from Equation (14.19) using the empirical E and C factors listed in Table 14.9. The subscripts A and B refer to acid and base, respectively ... 

TABLE 14.9 Drago-Wayland parameters using Equation (14.19) for selected acids (A) and bases (B). 

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 ... 

Eaq and Caq are the tendency of acid A and base B to undergo ionic and covalent bonding, respectively. Equation (2) resembles that proposed by Drago et al. (18) to model heats of complex formation of acids and bases in solvents of low dielectric constant. Only Lewis acids of ionic radius greater than 1.0 A obey Eq. (2). For all smaller Lewis acids, a third pair of parameters has to be introduced ... 

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. 

Double Heck reaction, 42 494 Double layer interface, 30 223-225 Double nucleophilic displacement, capped cyclodextrin, 32 437 Double-pulse method, 38 31 Double recognition models, 32 451 52 Doublet mechanisms, 30 43, 45, 47 Drago parameters, 38 212 Drougard-Decrooq equation, 30 345, 356, 371 Dry evaporation, perovskite preparation, 36 246-247... 

Pearson (2) and Drago and Weyland 38) proposed a two-parameter equation for the equilibrium constant K for the reaction between A and B... 

At present the dye techniques are very useful and economical but are somewhat approximate. Advances in use of indicator dyes for measuring surface acidity and basicity may be expected to include a two-parameter measure of acid or base strength similar to the E and C equation of Drago, and the use of fluorescent indicators for colored solids. 

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 ... 

Quantum chemical computations of H complexes heats formation in case of interaction of large organic molecules lead to high errors. A more perspective way is the use of well known relations of physical organic chemistry for this purpose. These equations allow to predict the heats of hydrogen-bonded or donor-acceptor complexes formation on the basis of donor (base) and acceptor (acid) empirical parameters. There are Drago and Weyland s equation [71]... 

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 and Wayland proposed a quantitative systan of acid-base parameters to account for reactivity by explicitly including electrostatic and covalent factors. This approach uses the equation — A// = + QCg where is the enthalpy of the reaction A + B AB... 

---