Carbon disulfide is a chemical compound with chemical formula CS2. It is a colorless liquid in appearance and is volatile in nature. It has a sweet odor like that of ether. Many students may also have doubts regarding whether CS2 is polar or not. In this article, I will answer this and will cover its properties and uses.
So, is CS2 polar or nonpolar? CS2 (Carbon disulfide) is nonpolar because of its symmetric (linear) shape. Although carbon and sulfur differ in their electronegativity and C-S bond is polar, the polarity of both opposite C-S bonds gets canceled by each other resulting in a nonpolar molecule.
Carbon disulfide exists in the liquid state at standard conditions of temperature and pressure. It smells sweet like ether.
This compound is considered as the building block in the world of organic chemistry. It is widely used in the industries as a non-polar solvent.
It is a highly flammable liquid. Its combustion produces SO2 and CO2 gas fumes.
CS2 (Carbon disulfide) + 3O2 (Oxygen) —-combustion—-> CO2 (carbon dioxide) + 2SO2(sulfur dioxide)
The molecular mass of this compound is 76.13 g·mol−1. It is calculated as
Mol mass of CS2 = 1 * 12(Mol mass of C) + 2 * 32(Mol mass of S) = 76.13 g·mol−1.
The chemical composition of this substance is such that it consists of 1 carbon and 2 sulfur atoms.
The carbon atom is the central atom surrounded by 2 sulfur atoms on both sides. The Sulfur atoms around both sides (left and right) create the shape of a molecule is linear.
The electronegativity of carbon is 2.55 and that of Sulfur is 2.58 due to which the C-S bonds become slightly polar.
The slightly polar bonds in opposite directions cancel out the polarity with each other and nullify the overall polarity of the molecule.
The dipole of the entire molecule turns out to be 0 D.
Difference Between Polar and Nonpolar Molecules
The molecules that are held by the covalent bonds can be polar. Let us understand the covalent bonds.
Covalent bonds are the types of chemical bonds in which atoms share electrons of each other to get stabilized.
These bonds can be single, double, and triple depending upon the basis of the number of electrons participated in bond.
Non-Polar Molecules: The non-polar molecules are the molecules in which the charges are uniformly spread across the molecule such that no atom share unequal charge.
The dipole moment of such molecules has zero value. The covalent bond formed between two atoms is non-polar if the atoms have equal electronegativity.
These molecules may also consist of polar bonds within them, but due to the symmetrical shape, the polarity of such bonds gets canceled by each other making the molecule a nonpolar.
Some of the examples of these molecules are BF3, Cl2, O3. You can check out the reason for the non-polarity of BeCl2.
Polar Molecules: The nonpolar molecules are the molecules that have unequal distribution of charge across its atoms.
The dipole moment of such molecules is always non zero. The bond formed by a diatomic molecule is said to be polar if they differ in their electronegativity.
This is because higher electronegative atom pulls the bonded electronegative charge slightly towards it and gains a partial negative charge.
Few examples of nonpolar molecules are HCl, HBr, etc. You can check out the reason for the polarity of HBr.
Why is CS2 a Nonpolar Molecule?
As discussed the molecule of carbon disulfide consists of 1 carbon and 2 sulfur atoms on its both sides and forms a symmetric linear-shaped molecule.
The symmetrically shaped molecules are usually nonpolar. Similarly, the CS2 molecule is non-polar because of following reason,
There exists a small difference between the electronegativity of carbon and sulfur atoms that makes the C-S a slightly polar bond.
Both C-S bonds have dipoles in opposite directions as a result it cancels each other and net dipole turns out to be zero.
Therefore, it is generally observed that symmetrically shaped molecules tend to be nonpolar in nature.
Instead of having polar bonds, the molecule is nonpolar.
Lewis Structure and Geometrical Structure of CS2
Lewis structure of a molecule is also known as electron dot structure because it represents the number of valence electrons of the molecule that take participation in the bond formation.
In lewis structure, the lines denote the bond formed in the molecule and dot represents the non bonded electrons.
Lewis structure is dependent on the octet rule. Octet rule concepts mean that the atom should have eight electrons in its outermost shell to achieve its stability.
In CS2 molecule, Carbon has 4 valence electrons and the Sulfur atom has 6 valence electrons. This makes a total of 16 valence electrons of the CS2 molecule.
Carbon is the least electronegative atom in the molecule therefore it becomes the central atom.
Both Sulfur atoms form a double bond with the carbon bond to complete their octet leaving behind two lone pairs on both Sulfur atom.
And the geometrical shape of the molecule becomes linear having sulfur atoms at both ends. The bond length of the C-S bond is around 155.26 pm.
Below is the image of the geometrical shape of the CS2 molecule.
Important points to determine the polarity of a molecule
While checking if a molecule is polar or not. You should note down the following properties that help to check its polar nature.
Let us check what the below factors actually means.
Electronegativity: The electronegativity of the atoms in a molecule must be noted down. If you see the difference between the electronegativity of its atoms. It means the bond formed by them is polar.
Two atoms that form a covalent polar bond will always differ in their electronegativity.
This is because a higher electronegative atom will attract the bonded electron pair towards its side and gain negative charge and other tom gets a partial positive charge.
The polarity of a molecule is directly proportional to the difference between the electronegativity of its atoms.
Dipole Moment: This term is used to measure the extent of the polarity of a molecule. The polarity of a molecule is directly proportional to its dipole moment.
Basically, It is the product of the charges on atoms and distance between the centers of their positive and negative charge.
It is denoted by D with its SI unit Debye.
Geometrical Shape: The shape of a molecule is a very important parameter that can make it polar or non-polar.
It is usually seen that geometrically distorted molecules are polar because they have charge imbalance.
Whereas the symmetrically shaped molecules are non-polar in nature because the charge distribution in these molecules is uniform.
Properties of CS2
- It exists as a liquid with a colorless appearance.
- In pure form, it smells sweet as ether. But commercially, it is added with impurities resulting in a foul smell.
- Its melting point is −111.61 °C or −168.90 °F and its boiling point is 46.24 °C and 115.23 °F.
- This compound is an organosulfur compound.
- At a temperature of 20 °C. Its solubility in water is 2.17 g/L.
- At a temperature of 25 °C, the vapor pressure of this compound is 48.1 kPa.
- It is volatile ie; evaporates at room temperature.
Uses of CS2
- This substance is widely used for the manufacturing of perfumes and other fragrance products.
- It is also used in the production of rayon, rubber in textile industries.
- This liquid is also present in the insecticides used in the crop fields.
- Carbon disulfide is considered as a building block in organic chemistry.
- In smaller quantities, it is used in various solvent extraction processes.
Carbon disulfide consists of 1 carbon atom and 2 sulfur atoms on both sides of carbon making a linear-shaped molecule.
Although there is a little difference between the electronegativity of Carbon(2.55) and Sulfur(2.58) that makes the C-S bond slightly polar, the molecule is nonpolar due to symmetric shape of CS2 molecule.
The dipole of both C-S bonds is equal and in opposite directions that cancel by each other making CS2 molecule non-polar.
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