Acid-Base Properties and Ion-Dipole Interactions

The favorability of acid-base reactions is affected, in pa by electrostatic interactions between charged atoms a dipoles within the same molecule. The equilibrium w shift in the direction of an ion that is stabilized 1 intramolecular ion-dipole interactions. 

The larger the charge and the closer the dipole is to t charge, the greater will be the stabilization ( destabilization). 

Display the dipole moment for methyl chloride. Is chlori at the -b or - end  

display electrostatic potential maps for acetUi chloroacetate, trichloroacetate, 2-chlorohutyrate a 4-chlorobutyrate anions. Compare potentials at the positi between the two oxygens. Classify the anions as havi large, intermediate or small charge in this region. 

Finally, examine the geometries of the anions, and classi the distance between the center of negative charge a the positive end of the dipole as small ( 2A), intermedi ( 3A) or large ( 3A). 

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The principal factors affecting solvent-ion interactions can be classified as ion-dipole, Lewis acid-base, hydrogen-bonding, solvent structural, and steric. The solvent obviously plays a major part in these interactions. Therefore, to interpret trends in conductance data, bulk solvent properties such as viscosity and dielectric constant should be considered. Table 1 lists selected physical properties for a number of organic solvents. 

A high dipole moment [jl will contribute to the chemical interaction between a polar solvent and ions as well as between the solvent molecules themselves and will, although physical in nature, be discussed in relation to the chemical properties of the solvent. According to the concept of soft and hard acids and bases the degree of polarizability is also important and will be discussed later. 

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