A thick viscous hydrocarbon with five to forty carbon atoms attached to a large number of hydrogen atoms, in liquid form at ambient temperatures, is essentially termed as oil. Oil is hydrophobic and lipophilic liquid i.e. it does not mix homogeneously in water but is miscible in other lubricants. Although hydrocarbons are both saturated and unsaturated, oil is customarily an unsaturated lipid that exists in liquid form at room temperature.
Is Oil Polar or Non-Polar? Oil is a nonpolar substance. It is a pure hydrocarbon wherein there are Vander Waal forces of attraction between the atoms in the molecule. Since there is no abundance of charge at any particular corner of the molecule, therefore the net dipole moment is 0D. Hence, oil is considered as a nonpolar molecule.
Organic Oil is produced by the extraction through animals, plants by the metabolic process. These can be consumed and widely used in food industries for cooking.
Crude Oil or Mineral Oil is the refined product also known as petrochemicals used majorly over the globe for the automotive engines and machinery. It is produced by the fossilization of algae over the years.
Polarity is determined by the virtue of the concentration of positive and negative charges at particular ends of a molecule.
When negative charges hoard up at one end of the molecule, creating a build-up of positive charges at the other end, then a dipole moment develops across the aforesaid molecule.
The subsistence of this dipole moment becomes an indication of the polarity of the molecule. If you want to look at the polarity of a gaseous molecule. Here is the article for the polarity of Ammonia.
The difference between polar and non-polar molecules can be drawn out as follows:
|Formation of strong H-bonds||Existence of Vander Waal forces|
|Asymmetrical structure||Symmetrical Structure|
|Presence of a net dipole moment||Absence of net dipole|
|Charge build-up at polar ends||No charge accumulation|
The polarity of any substance thus depends upon the following factors
- Electronegative difference between the atoms making the molecule
- Types of forces existing in the molecule
- The structure of the molecule (symmetric or asymmetric)
For molecules with weak van der Waal forces or London forces, polarity barely exists. Such molecules fall under the category of non-polar molecules.
Some of the examples of nonpolar molecules are HBr, H2S, etc. Here is the reason for the non-polarity of H2S.
Why is oil nonpolar in nature?
Oil principally contains long hydrocarbon chains. Such hydrocarbons demonstrate the existence of weak Van der Waal forces between them. The presence of Van der Waal forces is a strong indication of the absence of any kind of polarity in the molecule.
In oil, there is no major charge accumulation on one particular side of the molecule, thereby ruling out the possibility of the existence of a considerable net dipole moment across the molecule.
Polarity across a molecule rises when there is a difference between the electronegativity of atoms. In that case, the higher electronegative atom becomes a negative pole as the electron density increases on the more electronegative atom.
What are Vander Waal Forces?
Vander Waals forces are weak attractive and repulsive intermolecular forces that exist between the atoms or molecules.
They arise between uncharged atoms or molecules and depend upon the distance between them.
There are three kinds of Vander Waal forces:
- The Keesom interactions
- Debye forces
- London dispersion forces (which are dominant in unsaturated hydrocarbons i.e. Oil)
How these forces affect the polarity of oil?
Vander Waal forces are typically very different from ionic and covalent bonds. They are weaker in comparison and cannot be saturated.
For polarity, the H- Bonds so formed are mostly covalent in nature and result in unequal sharing of charge. This leads to amassing of charges at the ends of the molecule and develops a dipole moment, thereby resulting in polarity.
In contrast to covalent and ionic bonds, Vander Waal forces are so weak that they do not contribute at all to any kind of charge build-up.
This rules out the possibility for any dipole formation in the fat and oil molecules. Hence, the presence of Vander Waal forces in the oil molecules is the foremost indicator of the non-polarity of oil.
Oil- the unsaturated hydrocarbon
Structure & Formation
Fats and oils are esters which primarily compose three fatty acid units joined to glycerol. They are hence called triglycerides (because formed by three components and glyceride because of the combination of fatty acid and glycerol).
So, the basic structure can be described as three esters (same or different) replacing the three –OH groups in the glycerol molecule.
The process of formation can be described as:
- Three fatty acids react with glycerol (containing three –OH groups)
- A catalyst is used to accelerate the reaction
- The ester groups in the fatty acids replace the –OH group, forming glyceride
- The by-product so formed is water
Types of Triglycerides
These triglycerides are of two types:
- Simple triglyceride- wherein esterification occurs with the same fatty acid for all the three –OH ions on the three glycerol molecules.
- Mixed triglyceride- contains two to three different fatty acid components.
The simple triglycerides do not usually occur naturally. They are synthesized in the laboratories by performing an esterification reaction in the presence of a catalyst.
For the production of simple oils and fats, it is necessary that the three –OH groups present in the three glycerol molecules must be esterified with the same fatty acid. An example of a simple triglyceride is Tristearin.
Mixed triglycerides, on the other hand, can be obtained from naturally occurring fats and oils. Such substances contain two to three different ester groups that have replaced the –OH groups in the three glycerol molecules.
Properties of Oil
- Oils are hydrophobic in nature, i.e. they are immiscible in water.
- They are fat-loving (or lipophilic), i.e. they mix well with other fats, oils, or non-polar liquids.
- Oils are naturally colorless, odorless, and tasteless. The colors, stench, and flavor that is bracketed with certain oils are divulged by adding some foreign substances. Those substances are lipid-soluble and these oils absorb them.
- They have a density of about 0.8 gcm-3. Being lighter than water, they tend to float in the form of droplets over the water surface.
- Oils are poor conductors of heat and electricity. To minimize the loss of heat through the skin, applying oil materializes an excellent insulating layer.
- They can participate in a number of chemical reactions and can be used to develop other substances such as fatty acids, soaps, etc.
Applications of Oil
There are a number of areas of application of oil. Some of the various purposes that oil can be used for are:
- Cooking: Numerous edible oils (both vegetable and animal) are used in the preparation of food. They add to the flavor and texture of the grub.
- Cosmetics: Applying oil to hair for nourishment, luster, enhancement of growth, and prevention of tangles is now a prolonged practice.
- Religion: Religiously, oil is considered as a spiritual purifier and often used for anointing purposes. Aromatic oils are often used at various religious places to maintain the whiff and positivity in the environment.
- Painting: The pigments for coloring can be simply appended to oil, making it a suitable component for colors and paints. Oil paintings are always awe-inspiring and appealing to the eyes.
- Lubrication: Since they are non-polar in nature, they do not blend or assort easily into other substances. So, they are used for the lubrication of machines, engines, etc. at industrial levels and door or window handles, etc. at domestic levels.
Oil is a thick liquid substance considered as a hydrocarbon with 30 to 40 series of carbon atoms connected in a chain. Since it is hydrocarbon it has Vander Waal forces among the atoms in the molecule. There exists no-charge separation across the molecule due to which the molecule has no positive and negative poles generated. The dipole of the molecule is also zero making it a nonpolar molecule.