Tetrachloroethylene, also known as tetrachloroethene, or perchloroethylene, is a chlorocarbon having the formula C2Cl4. In 1821, British scientist Michael Faraday synthesized tetrachloroethylene by the thermal decomposition of hexachloroethane.
It is a colorless liquid frequently in use as a dry-cleaner for clothes, so it is sometimes named a “dry-cleaning fluid”.
Which category does the chemical C2Cl4 fall into, polar or nonpolar? Therefore, let’s find out.
Is C2Cl4 polar or nonpolar?
Tetrachloroethylene (C2Cl4) is a nonpolar molecule. Each C-Cl bond in C2Cl4 has a dipole moment, but the net dipole moment of C2Cl4 is zero because it is a planar symmetrical molecule. Opposite dipole moments in symmetrical molecules do tend to cancel each other out, resulting in a net dipole moment of zero, making the overall molecule nonpolar in nature.
Following are the factors affecting the polarity of individual atoms in C2Cl4 and the overall polarity of the molecules C2Cl4.
Electronegativity
Dipole moment
Molecular geometry
Electronegativity in C2Cl4
Electronegativity is the ability of an atom to attract bonding electrons to itself.
Ionic bonds are formed when there is a significant difference in the electronegativities of two different elements.
Covalent bonds are formed even when there is little to no difference in the electronegativity of the two elements.
Polar covalent bonds result from a relatively little change in the electronegativity of the two elements involved.
Chlorine has an extremely high electronegativity because it possesses 7 electrons in its valence shell and requires one more electron to be stable as a noble gas. The electronegativity value for chlorine is 3.16.
The electronegativity of carbon is 2.55, which is lower than that of chlorine. The electronegativity difference between chlorine and carbon is 0.61 units.
A bond is considered to be a polar bond when the polarity difference between the two atoms is greater than 0.5 units.
Hence, the bond between carbon and chlorine is polar because the polarity difference is 0.61 units.
Due to a minor excess of electron density, chlorine acquires a partial negative charge (Clδ⁻). While the carbon atom acquires a partial positive charge (Cδ+) due to a slight electron density deficiency. Due to this electronegativity difference, each bond in C2Cl4 has a polar character.
Dipole moment in C2Cl4
The dipole moment is the net product of charge and distance of the oppositely charged atoms present in a molecule. Differences in electronegativity generate dipole moments.
The dipole moment increases as the electronegativity difference increases. Another element affecting the size of the dipole moment is the space between the oppositely charged atoms.
The dipole moment (u) unit is Debye, which is equal to the product of distance (between oppositely charged atoms) and charge.
A red arrow represents the dipole moment of every C-Cl bond in C2Cl4. Because the opposing dipole moments cancel one other, the compound’s net dipole moment is zero.
When the net dipole moment is zero, the molecule will be non-polar in nature. Therefore, C2Cl4 is a nonpolar molecule.
Molecular geometry
Molecular geometry represents the 3D arrangements of atoms in a molecule. The geometry of C2Cl4 is trigonal planar with no lone pairs present in the central carbon atoms.
By using VSEPR theory, we can determine the molecular geometry of C2Cl4; for this purpose, we will use the AXN notation.
AXN notation for tetrachloroethene
In AXN notation A represents the central atom, so, A = carbon
X represents the total number of bonded atoms with the central atom, so, X = 3.
N represents the total number of lone pairs of electrons on the central atom, so, N = 0.
As we know that there are two central carbon atoms so there are two triangles overlapping each other. These two triangles make C2Cl4 a symmetrical molecule, this is also a reason that C2Cl4 has a net zero dipole moment, which makes it nonpolar.
Difference between polar and nonpolar?
Polar molecule
Non-polar molecule
Atoms must have a difference in electronegativity
Atoms may have the same or different electronegativity values
Unequal charge distribution overall
Equal charge distribution overall
Net dipole moment greater than zero
Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), Sulfur difluoride (SF2), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), sulfur trioxide (SO3), C2Cl4, etc.
The individual C-Cl bonds in the C2Cl4 molecule are polar in nature because the electronegativity difference between the atoms is 0.6. This electronegativity difference creates dipoles in the C-Cl bonds.
But the net dipole moment in C2Cl4 is zero because of the symmetrical trigonal planar geometry. The two symmetrical triangles cancel the dipole effects; hence C2Cl4 is non-polar in nature.
C2Cl4 is a liquid and is used in dry cleaning. Then why is it called a “dry” cleaning?
C2Cl4 is mostly used in dry cleaning clothes because it is a good organic solvent. It easily removes oil stains, grease, or any other organic compounds.
Although it is a liquid, the process is still called dry cleaning, which means it is water-free. Dry simply means that there is no water in the process.
How can we compare the polarity of C2Cl4 with that of CO2?
Both C2Cl4 and CO2 molecules are nonpolar. Because C2Cl4 and CO₂ have planar symmetry, their respective bond moments in the opposing directions cancel out each other.
Therefore, there is no net dipole moment in any case, so both are non-polar.
Summary
C2Cl4 is an sp² hybridized molecule having a trigonal planar geometry.
The Cl-C-Cl bond angle in the C2Cl4 molecule is 120.5⁰.
C2Cl4 is a planar symmetrical molecule.
Each C-Cl bond in C2Cl4 has a dipole moment, but due to the plane of symmetry, the net dipole moment of C2Cl4 is zero.
Therefore, the overall C2Cl4 is a non-polar molecule.
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
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