Ion dipole

Schematic representation of some of the lower frequencies in the ion-dipole complex for the Cl + MeCl m and the imaginary frequency of the transition structure, calculated using a 6-31G basis set. 

Van der Waals forces (Section 2 17) Intermolecular forces that do not involve ions (dipole-dipole dipole/mduced dipole and induced dipole/induced dipole forces)... 

Ab initio, gas phase calculations found two minima and one maximum for the reaction coordinate, leading to an exothermic formation of the tetrahedral complex. Oneminimum is an ion-dipole... 

Other factors that can stabili2e such a forming complex are hydrophobic bonding by a variety of mechanisms (Van der Waals, Debye, ion-dipole, charge-transfer, etc). Such forces complement the stronger hydrogen-bonding and electrostatic interactions. 

Polymer/Polymer Complexes. PVP complexes with other polymers capable of interacting by hydrogen-bonding, ion-dipole, or dispersion forces. For example mixing of PVP with poly(acryHc acid) (PAA) in aqueous solution results in immediate precipitation of an insoluble complex (113). Addition of base results in dismption of hydrogen bonding and dissolution (114—116). Complexes with a variety of poly-acids (117) and polyphenols (118) have been reported. The interest in compatibiHty on a molecular level, an interesting phenomenon rarely found to exist between dissimilar polymers, is favored by the abiHty of PVP to form polymer/polymer complexes. 

Dissolution of ionic and ionizable solutes in water is favored by ion—dipole bonds between ions and water. Figure 6 illustrates a hydrated sodium ion,... 

Fig. 6. Hydrated sodium ion,, in aqueous solution (4).The H2O molecules form ion—dipole bonds to the central metal ion. The waters are in...

Ion-Dipole Forces. Ion-dipole forces bring about solubihty resulting from the interaction of the dye ion with polar water molecules. The ions, in both dye and fiber, are therefore surrounded by bound water molecules that behave differently from the rest of the water molecules. If when the dye and fiber come together some of these bound water molecules are released, there is an increase in the entropy of the system. This lowers the free energy and chemical potential and thus acts as a driving force to dye absorption. 

Crown ether (Section 16.4) A cyclic polyether that, via ion-dipole attractive forces, forms stable complexes with metal ions. Such complexes, along with their accompanying anion, are soluble in nonpolar solvents. 

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. 

Experimental pK data suggest that eyano substitution can exert substantial long-range effeets on phenol aeidity, but the reason for these effeets is not obvious. If ion-dipole interaetions were to blame, the effeet would fall off with increasing ion (0 ) - dipole (CN) separation. If electron delocalization were responsible, then the effeet would be aeeompanied by eharge transfer between the ionie site (O ) and other atoms in the moleeule. 

Decide if ion-dipole interactions are responsible for the observed substituent effects. Obtain the charge on carbon and nitrogen in each cyano group. What evidence is there for a polar CN bond Should the ion (O )-dipole (CN) interaction be stabilizing or destabilizing Can these interactions explain the trends in electrostatic potential (Hint Focus on changes in O—CN distance and in orientation of the cyano group.)... 

The precipitate redissolves in excess soluble cyanide, and the complex ion is probably an ion-dipole co-ordination compound, i.e. 

Ion-dipole interactions interact over longer distances. Their mean interaction energy 0id decreases with r-4 3) ... 

Hydrophilic hydration signifies that a strong energetically favored direct interaction exists between dissolved polar or ionic particle and the surrounding water molecules by ion-dipole-, dipole-dipole-interactions and/or hydrogen bonds. 

In this review, recent development of active transport of ions accross the liquid membranes using the synthetic ionophores such as crown ethers and other acyclic ligands, which selectively complex with cations based on the ion-dipole interaction, was surveyed,... 

Ionophores constitute a large collection of structurally diverse substances that share the ability to complex cations and to assist in the translocation of cations through a lipophilic interface.1 Using numerous Lewis-basic heteroatoms, an ionophore organizes itself around a cationic species such as an inorganic metal ion. This arrangement maximizes favorable ion-dipole interactions, while simultaneously exposing a relatively hydrophobic (lipophilic) exterior. 

---