Why is Acetone Polar?
Solvents are basically categorized as polar and non-polar. The polarity of a solvent can be determined approximately by the dielectric constant of it. The polarity of water is determined by its dielectric constant being 80.10 which indicates that water is highly Polar. If the dielectric constants of the solvents are less than 15 then they are treated as non-polar. If the solvent is able to decrease the strength of the electric field that is surrounding the particle that is charged, then the solvent is considered to be having high dielectric constant. The decrease in the electric field strength of the charged particle by the solvent is compared with the field strength of the particle in vacuum. This is done to say that solvent has the capacity to decrease the internal charge of the particle.
Accurate measurement of polarity is not only done through dielectric constant. Some of the other measurements of polarity are Grunwald Winstein mY scale, Kosower’s Z scale, donor number, and donor acceptor scale. To understand which kind of solute particles are dissolved by the solvent, its dipole moment, polarity, hydrogen bonding and polarizability are important. The dielectric constant of acetone is 21 and its dipole moment is 2.88 Debyes.
Acetone is more Polar compared to some of the other organic solvents. One of the reasons for it is that the hybridization state of the carbon atom that is attached to the oxygen atom in acetone is sp2. In the case of ethanol, the hybridization state of the carbon atom attached to the oxygen atom is sp3. The sp2 hybridized carbon is considered to be behaving as more polar than sp3 carbon. Hence, acetone is aprotic polar solvent while ethanol is protic polar solvent.
Polar solvents are again classified as protic and aprotic. Protic solvents can dissolve the substances by bonding the anions in them with the hydrogen ion. Acetone is aprotic solvent. As it has large dipole moments it has the ability to separate the anions and cations of the solute particles first. Later, it starts the dissolution by attaching its negative dipole with the cation of the solute.