solvent: A liquid that dissolves anothersubstance or substances toform a solution. Polar solvents arecompounds such as water and liquidammonia, which have dipole momentsand consequently high dielectricconstants. These solvents arecapable of dissolving ionic compoundsor covalent compounds thationize. Nonpolar solventsare compounds such asethoxyethane and benzene, which donot have permanent dipole moments.These do not dissolve ioniccompounds but will dissolve nonpolarcovalent compounds. Solvents canbe further categorized according totheir proton-donating and acceptingproperties. Amphiprotic solvents selfionizeand can therefore act both asproton donators and acceptors. A typicalexample is water:
2H2O?H3>O+ + OH-
Aprotic solvents neither accept nor donate protons; tetrachloromethane(carbon tetrachloride) is an example.
A liquid capable of dissolving other materials (solids, liquids, or
gases) to form a solution. The solvent is
generally the major component of the solution. Solvents can be divided into classes,
the most important being:
Polar. A solvent in which the molecules
possess a moderate to high dipole moment
and in which polar and ionic compounds
are easily soluble. Polar solvents are usually poor solvents for non-polar compounds. For example, water is a good
solvent for many ionic species, such as
sodium chloride or potassium nitrate, and
polar molecules, such as the sugars, but
does not dissolve paraffin wax.
Non-polar. A solvent in which the molecules do not possess a permanent dipole
moment and consequently will solvate
non-polar species in preference to polar
species. For example, benzene and tetrachloromethane are good solvents for iodine and paraffin wax, but do not dissolve
sodium chloride.
Amphiprotic. A solvent which undergoes
self-ionization and can act both as a proton
donator and as an acceptor. Water is a
good example and ionizes according to:
2H2O = H3O+ + OH–
Aprotic. A solvent which can neither accept nor yield protons. An aprotic solvent
is therefore the opposite to an amphiprotic
solvent.
