5. What is a Solvent?
• The liquid in which a solute is dissolved to form a
solution.
• The term “solvents” refers to liquid organic
chemicals used to dissolve solid materials.
• A solvent is a substance that dissolves a solute,
resulting in a solution.
• A solvent is usually a liquid but can also be a
solid or a gas.
• The maximum quantity of solute that can
dissolve in a specific volume of solvent varies
with temperature.
7. Let's see an example.
Suppose that you have a mixture of sugar in vegetable oil (it
tastes sweet!) and you want to separate the sugar from the oil.
You observe that the sugar particles are too tiny to filter and you
suspect that the sugar is partially dissolved in the vegetable oil.
What will you do?
8. How about shaking the mixture with
water
Will it separate the sugar from the oil?
Sugar is much more soluble in water
than in vegetable oil, and, as you know,
water is immiscible (=not soluble) with
oil.
Did you see the result? The water phase is
the bottom layer and the oil phase is the
top layer, because water is denser than
oil.
*You have not shaken the mixture yet, so
sugar is still in the oil phase.
9. By shaking the layers (phases) well,
you increase the contact area between
the two phases. The sugar will move
to the phase in which it is most
soluble: the water layer
10. Now the water phase tastes sweet, because the sugar is moved
to the water phase upon shaking.**You extracted sugar from
the oil with water.**In this example, water was the extraction
solvent ;the original oil-sugar mixture was the solution to be
extracted; and sugar was the compound extracted from one
phase to another. Separating the two layers accomplishes the
separation of the sugar from the vegetable oil
12. Polar & Non-Polar Solvents
Polar solvents have large dipole moments (aka “partial charges”);
they contain bonds between atoms with very different
electro negativities, such as oxygen and hydrogen.
Non polar solvents contain bonds between atoms with similar
electro negativities, such as carbon and hydrogen
(think hydrocarbons, such as gasoline).
Bonds between atoms with similar electro negativities will lack
partial charges; it’s this absence of charge which makes these
molecules “non-polar”.
13. Molecules with a hydroxyl group (-O-H) are generally soluble in water.
Other substances, like fats, are non-polar . They will not dissolve in
water.
These substances are neutral and there is no excess charge at one
end of the molecule. Examples are, benzene (C6H6), and carbon tetrachloride (CCl4). Benzene will dissolve in carbon tetra-chloride.
Molecules that are hydrocarbons (mostly C and H) will dissolve in
other hydrocarbons.
A basic rule is: Like dissolves in Like .
This means that, in general, polar substances will dissolve in other polar
substances, and that non-polar substances will dissolve in other non-polar
substances.
Polar substances will not dissolve non-polar substances.
14. A solvent is a liquid that serves as the medium for a
reaction.
It can serve two major purposes:
(Non-participatory) to dissolve the reactants.
Remember “like dissolves like” ?
Polar solvents are best for dissolving polar reactants (such as
ions);
nonpolar solvents are best for dissolving nonpolar reactants (such
as hydrocarbons).
Participatory: as a source of acid (proton), base (removing
protons), or as a nucleophile (donating a lone pair of electrons).
15. Remember water & oil example ?
• Think of how oil and water don't
mix. Water is polar and oil is nonpolar.
• A polar molecule has poles, basically
some areas are charged negatively
and some are charged positively.
• A soap is a salt of a fatty acid, it has
a polar end that "likes" water and a
long non-polar chain that "likes" oil.
16. Uses of Solvents
As a Solvent
• Dissolution
• Extraction
• Degreasing
• Inks, dyes, paints,
coatings
• Dilution, dispersal
• Dry cleaning
As Something Else
• Fuels
• Feedstocks
• Drugs of abuse
• Beverages
• Antifreeze
• Explosives
• Pollutants
17. Removing water from Solvents
There are various ways of removing water and other impurities
from a solution.
This can become a major task once the used reagents are also
sensitive towards water.
The drying agents commonly used in the organic laboratories
are the anhydrous forms of calcium chloride (CaCl2),
sodium sulfate (Na2SO4) Calcium sulfate (CaSO4 and
magnesium sulfate (MgSO4).
18. Pore sizes in adsorbents may
be distributed throughout the solid.
Pore sizes are classified generally into 3 ranges:
macropores have "diamaters" in excess of 50-nm,
mesopores (also known as transitional pores) have
"diameters" in the range 2 - 50-nm, and
micropores have "diameters" which are smaller
than 2-nm.
20. 3A Molecular Sieves : 3A (pore size 3 ): Adsorbs NH 3, H2O, (not C2H6), good for
drying polar liquids
4A Molecular Sieves : 4A (pore size 4 ): Adsorbs H 2O, CO2, SO2, H2S, C2H4, C2H6, C3H6,
ethanol. Will not adsorb C3H8 and higher hydrocarbons. Good for drying nonpolar
liquids and gases.
5A Molecular Sieves : 5A (pore size 5 ): Adsorbs normal (linear) hydrocarbons to
n-C4H10, alcohols to C4H9OH, mercaptans to C4H9SH. Will not adsorb isocompounds
or ring structures with more than four carbon atoms.
10X Molecular Sieves : 10x (pore size 8 ): Adsorbs branched hydrocarbons and
aromatics. Used for drying gases.
13X Molecular Sieves : 13x (pore size 10 ): Adsorbs di-n-butylamine
(not tri-n-butylamine).
21. Applications
Why is acetone, instead of water, used to extract chlorophyll and other green
leaf pigments?
The pigments and the rest of the leave stuff will just stick together in
water. Acetone is an organic solvent that can separate the aqueous
impurities from the pigments in leaves.
Drying of Acetone. Acetone has been dried with a wide
spectrum of desiccants. Thus, alumina, calcium chloride,
phosphorus pentoxide, and 4A molecular sieves, as well as
calcium and (anhydrous) cupric sulfate, have all been used.
22. Applications
Ethanol is used in perfumes & after shaves.
Acetone is used in Chlorophyll Extraction because it is an
organic solvent.
It can split the aqueous impurity from the pigment in leaves
unlike when water is used.
Isopropyl Alcohol used as a solvent in bulk drug API mfg.
23. Solvents in Rubber & Polymers
Making better products...
Solvents are used in many different processes within the
polymer manufacturing industry,
e.g. in the production of rubber or tyres and in polyolefin's
manufacturing.
Dearomatised aliphatic hydrocarbon solvents are applied in
the production of tyres to ‘glue’ together the many different
pieces and layers of rubber, ensuring they are safe and
durable. Methyl isobutyl ketone (MIBK) is used as a raw
material in the manufacture of rubber antiozonants.
24. In the shoe industry, a major breakthrough occurred in 1928 when
polychloroprene was first introduced.
The first, simple formulation is still manufactured and is used
worldwide because the glue can be easily prepared by simply making a
solution of the polymer.
This gives a product with good adhesion to various substrates.
Many new products are available today as potential replacements. Hot
melt adhesives can be used in some applications but they still require
solvents for cleaning, degreasing, and swelling.
Water-based adhesives are the most likely replacement product.
25. MOLECULAR SIEVES FOR SOLVENT DRYING:
This market includes the drying of solvents used for cleaning and/or purification of a
material.
This type of drying is found in chemical plants, refineries, manufacturing plants, etc.
where a material is rinsed by a hydrocarbon stream, then recycled, dried, and returned to
cleanse the material.
For example, an acetone liquid stream is used to wash a thread used for making tea
bags
REPRESENTATIVE TYPES OF SOLVENTS BEING RECOVERED
Acetates
Acetone
Benzene
(MIBK)
Chloroform
Cyclohexanone
Ethanol
Ether
Freons
Gasoline
Heptane
Hexane
Isopropyl Alcohol
(IPA)
Methanol
Methyl Ethyl Ketone
(MEK)
Methyl Isobutyl
Ketone
Methylene Chloride
Mineral Spirits
Pentane
Perchloroethylene
Propanols
Tetrahydrofuran (THF)
Toluene
Trichloroethane
Trichloroethylene
Xylene
26. Solvent drying guide
TO DRY
USE ONE OF THE FOLLOWING DRYING AGENTS
Alcohols
Anhydrous forms of potassium carbonate; anhydrous magnesium or
calcium sulphate; quicklime.
Alkyl halides
Aryl halides
Anhydrous calcium chloride; anhydrous forms of sodium sulphate,
magnesium sulphate, or calcium sulphate; sodium pentoxide.
Saturated and
Anhydrous calcium chloride or sulphate; metallic sodium; phosphorus
Aromatic hydrocarbons pentoxide.
Aldehydes
Ketones
Anhydrous sodium sulphate; anhydrous magnesium or calcium
sulphate.
Anhydrous sodium sulphate; anhydrous magnesium or calcium
sulphate; anhydrous potassium carbonate.
Organic bases
(amines)
Solid potassium or sodium hydroxide; quicklime; barium oxide.
Organic acids
Anhydrous sodium sulphate; anhydrous magnesium or calcium
sulphate.