Carbon Tetrachloride (CCl4) is also known as carbon chloride, benziform, or methane tetrachloride.
This blog post covers the details about what the polarity of a molecule is, and whether the CCl4 molecule is polar or non-polar.
Its Molecular Geometry, Polarity Lewis Structure, and Applications with detailed answers to multiple frequently asked questions.
So before diving into the polar nature of CCl4, let’s first understand what is the difference between polar and non-polar molecules and how we define them.
What Is Meant By Polar And Non-Polar Compounds?
When you hear the phrase “polar,” you probably think of the earth’s north and south poles. These north and south poles are placed at opposing ends of the globe, similar to how a battery might have a positive and negative pole.
Polarity is also present in molecules and atomic bonds. Let’s start with a quick review of what polar and non-polar molecules are.
A polar molecule has an unequal distribution of electrons on the bonded atoms.
These are molecules with a positive net dipole moment. Polar molecules also exhibit asymmetric geometrical structures.
A polar molecule is one where the atoms that make up the molecule have unequal electronegativity. This creates an imbalance of electrical charge across the molecule, which gives it a dipole moment.
The two atoms form a polar covalent bond if their electronegativity differences are between 0.5 and 2.0.
Examples of Polar Molecule
- Water is a polar molecule. The reason is that both hydrogen atoms are on one side of the oxygen atom rather than evenly spaced in the H2O molecule.
- NH3 (Ammonia) is a polar molecule because it possesses three dipoles that do not cancel each other and have net dipole moments. In addition, the partial charges are distributed unequally throughout the NH3
- Sulfur dioxide ( SO2)
- Hydrogen sulfide (H2S)
- Ethanol (C2H6O)
Be aware that a molecule can include polar bonds while being nonpolar. Carbon dioxide, for example, contains four polar bonds but the dipole moments of the molecule cancel each other out, making the molecule nonpolar.
If the molecule has a symmetrical shape, then it is non-polar
A non-polar molecule, on the other hand, is one where the atoms have equal electronegativity. This means that there is no charge imbalance across the molecule, and it does not have a dipole moment.
The bond will be nonpolar if the electronegativity difference between two atoms is less than 0.5, even though the only nonpolar molecules are those produced with identical atoms.
Examples of Non-Polar Molecules
- H2, O2, Cl2, and N2 are all homo-nuclear diatomic elements. (These molecules are truly nonpolar.)
- Carbon tetrachloride (CCl4)
- Methane (CH4)
- Benzene ( C6H6)
- Ethylene ( C2H4)
- Carbon dioxide (CO2)
- Many hydrocarbons i.e. toluene and gasoline
- Organic molecules
At this point, you are very much clear about the concept of polar and non-polar molecules, let’s take a look at the detailed polarity of CCl4.
Carbon tetrachloride is a non-polar molecule. This means that the electrons distribute uniformly around the carbon atoms and the molecule does not have a net dipole moment.
Carbon tetrachloride is composed of one carbon atom and four chlorine atoms. The carbon forms a single polar covalent bond with each chlorine atom.
The distribution of electrons around the molecules is such that the molecule has no net dipole moment. This makes it a non-polar molecule.
While Carbon tetrachloride is considered a non-polar molecule, it should note that it could form hydrogen bonds with other molecules. This is because the lone pairs of electrons on the chlorine atoms can interact with the hydrogen atoms of other molecules.
That is the obvious answer to the polarity of carbon tetrachloride.
However, discussing the polarity of molecules in general and looking at carbon tetrachloride and its facts to understand why it is nonpolar in nature would be beneficial.
Molecular Geometry of Carbon Tetrachloride (CCl4)
When it comes to carbon tetrachloride geometrical structure, the four C-Cl bonds have symmetric orientations in comparison to other C-Cl bonds. The center element is carbon, which is linked to four other atoms by C-Cl bonds.
As we know, carbon has four valence shell electrons and all of them collaborate with four chlorine atoms in the formation of a covalent bond, leaving no lone pair on the carbon atom.
The bond angle is approximately 109.5 degrees, and it has a tetrahedral shape.
With one s orbital of carbon and three p orbitals, carbon tetrachloride shows sp3 hybridization
Factors That Predict the Polarity of the Molecule
We can predict whether Carbon Tetrachloride (CCl4) is polar or non-polar by considering the following factors.
Atoms’ electronegativity indicates their tendency for attracting electrons to themselves. If the electronegativity difference between bonded atoms is higher, polarity will be high for bonded atoms.
C atom has an electronegativity of 2.5 and Cl has an electronegativity of 3.0, resulting in a polar covalent bond.
Carbon tetrachloride has four (C-Cl) polar bonds; however, the molecule is nonpolar because the polarity of the bonds is cancelled by the symmetric tetrahedral geometry.
Shape or Geometry
The main deciding factor that predicts whether it is polar or non-polar is its molecular geometry. It molecule has a tetrahedral geometry.
In the CCl4 Lewis structure, there are no lone pairs on the central atom; hence, there is no distortion.
Due to its tetrahedral symmetrical shape, the polarity of each C-Cl bond cancels out. The resulting polarity is hence zero, which makes CCl4 a non-polar molecule.
Polar molecules have a net dipole moment, while those with a zero dipole moment are nonpolar.
It has no dipole moment because its four C-Cl bonds arrange at the edges of the symmetrical tetrahedron and completely cancel one another. Therefore, CCl4 is a non-polar molecule.
So, based on these properties, we can say that carbon tetrachloride is a non-polar molecule because it has a symmetrical shape and zero dipole moment
What Makes CCl4 Non-Polar?
Lewis structure of the molecule shows it’s a tetrahedral molecule. C has an electronegativity of 2.5, whereas Cl has an electronegativity of 3.0, resulting in a polar covalent bond.
The four polar bonds of carbon tetrachloride (CCl4) are canceled by the symmetric tetrahedral structure, making the molecule nonpolar.
We can see the partial charges by drawing the dipole moment for this bond. Therefore, it is a nonpolar molecule.
Polar molecules are attracted by other polar molecules (like H20), while non-polar molecules are repelled by polar molecules like water.
Therefore, when you are trying to determine whether something will dissolve in water, this information helps you to figure out the right decision. If the molecule is polar, it stands a good chance of dissolving; if it’s non-polar, it probably won’t dissolve.
Molecular Geometry: What is It and How Does it Work?
Preparation of Carbon Tetrachloride (CCl4)
Did you know that non-polar CCl4 is not a naturally occurring compound? It synthesizes artificially.
It does not exist naturally, but it’s found in the environment because it is difficult to break down and has accumulated over time because of human activity.
In the mid-1800s, French scientist Henri Victor Regnault reported the first discovery of carbon tetrachloride. It was initially prepared (1839) by mixing chloroform with chlorine
CHCl3 + Cl2 → CCl4 + HCl
Later, Carbon tetrachloride was synthesized by the processing of carbon disulfide with chlorine at temperatures of 105 to 130 degrees in the 20th century.
CS2 + 3Cl2 → CCl4 + S2Cl2
However, nowadays Carbon tetrachloride is prepared by the chemical reaction of methane with chlorine under specific conditions.
CH4 + 4Cl2 → CCl4 + 4HCl
Physical Properties of Carbon Tetrachloride (CCl4)
- CCl4 is a colorless liquid that readily evaporates into the atmosphere.
- It has a pleasant odor.
- We can detect CCl4 at low concentrations due to its smell.
- CCl4 is non-flammable and does not dissolve readily in water.
Chemical Properties of CCl4 of Carbon Tetrachloride (CCl4)
- The boiling point of CCl4 is 76 ⁰ C.
- CCl4 has a melting point of around -23 ⁰ C.
- The density of carbon tetrachloride is 1.5867 g cm-3.
- At 20 ⁰ C, the CCl4 molecule has a vapour pressure of about 11.9 KPa.
- In water, the odor threshold is 0.52 mg/l, whereas, in air, it’s less than 64.1 mg/m3 (10 ppm).
Useful Aspects of Carbon Tetrachloride (CCl4)
- It is an excellent source for making chlorine-based organic compounds.
- As a solvent, carbon tetrachloride (CCl4) is used for dissolving nonpolar compounds such as fats and oil.
- Used in fire extinguishers since it helps to prevent fires by extinguishing the flames.
- As CCl4 is a non-polar molecule, that is why it’s a good solvent for non-polar compounds.
- Owing to the unavailability of the hydrogen atom, it is also very useful in NMR spectroscopy.
Carbon tetrachloride production has been steadily declining since the 1980s due to the detrimental environmental effect. The Montréal Protocol restricted the production of CCl4 because carbon tetrachloride is a vital component in the manufacturing of CFCs. Carbon tetrachloride production has decreased because of its negative health consequences, and now it is rarely utilized as a solvent.
Dangerous Aspect of Carbon Tetrachloride (CCl4)
- CCl4 is toxic to the liver.
- The high amount of CCl4 can be harmful not just to the liver but also to the kidneys and nervous system.
- Carbon tetrachloride poisoning can result in a coma or death.
- People may suffer from headaches, nausea, dizziness, and vomiting.
- Exposure to the CCl4-related chemical also increased the risk of cancer.
While the electronegativity of chlorine (Cl) and carbon (C) differ, giving in polar character in the C-Cl bonds, four C-Cl bonds neutralize each other’s polarity, resulting in a nonpolar CCl4 molecule. In other words, the bond dipoles cancel out completely due to the molecule’s symmetrical linear structure. As a result, the molecule has no net dipole and is hence non-polar.
So, I attempted to address all the reasons for the nonpolar behavior of Carbon Tetrachloride in this blog post.
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Why water is polar and CCl4 non-polar?
The electrons of the hydrogen (H) atoms are “pushed” towards the oxygen (O2) atoms, making H2O a polar molecule.
Carbon tetrachloride (CCl4) is nonpolar because the polarity of the bond cancels by symmetric tetrahedral shape. However, when other atoms replace some of the Cl atoms, the symmetry is broken and the molecule becomes polar
Why CCl4 is non-polar but CHCl3 is polar?
Because of the symmetrical geometrical structure of the CCl4 molecule, the bond polarity cancels out which makes CCl4 non-polar. Because of its tetrahedral molecular shape and the difference in electronegativity of C, H, and Cl, CHCl3 is polar.
Chlorine atoms are more electronegative than carbon and hydrogen atoms in CHCl3 and they lie at three of the pyramid’s vertices, pulling the negative charge in their direction, resulting in a polar molecule.
Why CCl4 does not dissolve in water?
Molecules have the property “like dissolve like” and we know CCl4, is a non-polar molecule, it can only be dissolved in non-polar solvents like oil, benzene, hexane, etc.
However, because water is a polar solvent and it can dissolve only polar substances like salts, HCl, etc. Because of this reason, CCL4 does not dissolve in polar solvents.