Solvents, acceptor number inert

The best-known solvent parameters are the donor number [21] and acceptor number [22] proposed by Gutmann and coworkers. The donor number (DN) for a donor solvent D is defined as the positive value of the enthalpy difference AH (kcalmol ) for the reaction of D with an acceptor-halide SbCls (D + SbCls D SbCls) in an inert medium such as 1,2-dichloroethane. DN is a fair measure for the donor properties of a solvent. The correlations of DN with the solvation energies are known to be good particularly for solvation of cations. A typical example [19] is shown in Fig. 3. 

Alternatively, acceptor numbers of cations, AN, were obtained directly by the use of solvatochrontic indicators in inert solvents. The indicator used by Linert et al. 

The enthalpy change during donor-acceptor adduct formation has been related by Drago to the sum of two terms (1) the product of the electrostatic properties of the acid and the base, Ef. and E and (2) the product of their tendency toward covalent bonding, Ca and Cb [10]. For the particular case, where the acceptor is specified to be SbCb (and the inert solvent is 1,2-dichloroethane), the negative of this enthalpy change (in kcal mol", 1 cal = 4.184 J) is the Gutmann donor number, DN [2,11]. These concepts are further discussed in Chapter 3. 

Let us consider a system with PEA molecules and N2 molecules of an inert solvent (N = Nj + N2). The number of proton donors of type 1 (-OH) is N, of proton acceptors of type 1 (-OH) is N, and of proton acceptors of type 2 (-0-) is wNi. Let there be hydrogen bonds OH OH, N 2 intermo-lecular bonds OH O-, and B intramolecular bonds OH O- in the system. The number of free proton donors is... 

Gutmann [Gu 67] made systematic examinations with a large number of solvents, which were characterized by their affinities towards antimony(V) pentachloride as the reference acceptor. Gutmann s proposed donicity value is the heat of solvation of antimony(V) chloride by various solvents (in dilute solutions prepared in an inert solvent), determined calorimetrically and expressed in kcal/mole. 

The hydrogen bond donating powers of water molecules and alcohols are comparable, both for the monomers in inert solvents and for the bulk solvents. Nevertheless, our results show that the primary solvation number for hydrogen bond acceptor solutes (such as Mc2CO, MeCONMc2 or anions) is usually at a maximum for aqueous solutions, but considerably less for methanolic solutions. 

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