Basity

Gas-phase basity and proton affinity values for 3,4,6,7,8,9-hexahydro-2/f-pyrido[l,2-n]pyrimidine were determined and they were compared to other super bases, including its lower and higher piperidine ring homologs (94JP0725, 01JPO25). 

The new names acity and basity were chosen because, although they are obviously kinds of acidity and basicity, they are neat (bulk) solvent properties involved in solute solvations. Such solvent properties cause specific local electrostatic solute/solvent interactions without major covalency changes and, therefore, are usually omitted from equations describing chemical reactions [265]. 

Table 7-6. Selection of values of solvent adty, Ay and solvent basity. By for 34 solvents, calculated according to Eq. (7-63) [265].

The mixture was warmed to 20°C stirred wAh i N NaOH (300 mL) for 2 hr and the organic layer separated The CHCI3 solution was extracted with 1 2 N HCI, the acidic solution was basitied and extracted wAh ether After removal of unreacted aldehyde (with NaHSOa) and evaporation of the solvent the residue (23 g) deposAed 8 g of 3 (32%), mp 105-109 0, mp 114 115°C from EtOAc... 

The extraction (and hence the transport) efficiency depends on several diluent factors such as Schmidt empirical diluent parameter [124,125], the Swain s acity and basity parameters along with the Dimroth and Reichardt polarity indices [126], dielectric constant [127], refractive index [127] and viscosity [127], and the Hildebrand s solubility parameter [128]. The permeability coefficients (Paio) were computed from the Wlke-Chang, Scheibel, and Ratcliff [129,130] equations, which compared reasonably well with the experimentally determined values as shown in Table 31.10. Efiiassadi and Do [131] have, on the other hand, taken into account only the viscosity and solubility effect of the diluent and the carrier immobilized in SLM. They have reported that these two factors influenced the transport rates significantly. 

Taft, R.W., Abboud, J.-L.M. and Kamlet, M.J. (1984). Linear Solvation Energy Relationships. 28. An Analysis of Swain s Solvent Acity and Basity Scales. J.Org.Chem., 49,2001-2005. 

The Swain Equation (34) provides very accurate predictive power for a limited range of solvents and processes based on a statistical analysis of a five-parameter equation. The origins of the Swain parameters are not explicit, although the acity (A) and basity (B) coefficients are related to electrophilic and nucleophilic processes respectively. Many fundamental processes have been implicated in solvent effects and the equation of Koppel and Palm (Equation 37) incorporates the major factors thought to be involved. 

Swain et al. (1983) have proposed a pair of parameters, A. and B., called acity and basity, coinages to imply similarity to acidity and basicity, but properties of the bulk solvents rather than the molecules. They fitted data for a great many phenomena (reaction rates, equilibria, spectral shifts) in a variety of solvents to equations of the form of Equation 4.5 ... 

A. Acity anion-solvating tendency (see S.) B. Basity cation-solvating tendency. (Bilinear Swain etal. (1983)... 

An acid (Lewis acid) is an electron acceptor while a base (Lewis base) is an electron donor. The degree of acidity or basity is dependent on the materials in contact. An acidic surface will be wetted by a basic fluid while a basic surface will be wetted by an acidic fluid. A basic fluid will not wet or adhere well to a basic surface and vice versa. An amphoteric material is one that can act as either an acid or a base in a chemical reaction, depending on the nature of the other material. An example of an amphoteric material is aluminum. 

---