Van der Waals forces
1. Dipole – Dipole Interactions
When the two polar molecules approach each other, an electrostatic force occurs between their opposite poles. In this way, the attraction force formed between polar molecules called dipole – dipole bond.
2. Ion – Dipole Interactions
The interaction between an ion and a polar molecule (permanent dipole) is called an ion – dipole bond. The ion-dipole bonds are the attraction forces between the bu + ”charged ion and the iyon -” pole of the polar molecule, between the charged, – ”charged ion and the iyon +” pole of the polar molecule.
3. Induced dipole interactions
a. Ion – induced dipole interactions
These are interactions that occur as a result of the dissolution of an ionic substance in the apolar solvent.
For example, the dissolution of KCl in benzene (C6H6) results in ion-induced dipole interactions.
b. Dipole – induced dipole interactions
These are interactions that occur as a result of the dissolution of an apolar molecule in a polar solvent. For example, the dissolution of the iodine solid (I2) in ethanol (C2H5OH) results in dipole-induced dipole interactions.
c. London forces (induced dipole – induced dipole)
The instantaneous polarity is formed by the movement of the electrons of the atoms in the molecules. The attraction forces between molecules with instant polarity are called London forces. The noble gases such as H2, Cl2, O2, CO2 and CH4, liquid molecules of London are seen in liquid form. London forces are much weaker than other van der waals gravity forces. Therefore, these substances have low boiling points.
The strength of London forces,
molecular weight increases with increasing.
increases as the contact surface increases.