CCl4 (carbon tetrachloride) also known as tetrachloromethane is a dense, colorless, volatile, highly toxic, and non-flammable liquid. It has a peculiar odor and belongs to the organic halogen compound family. It is a tetrahedral and non-polar molecule comprising three Cl-C-Cl bonds with a bond angle of 109.5°.
CCl4 was first prepared in 1839 by reacting chloroform with chlorine. Commercially, carbon tetrachloride is manufactured by reacting chlorine with methane or carbon disulfide. The boiling point of CCl4 is 77°C while its freezing point is -23°C. Since its density is higher than water, CCl4 isn’t soluble in water.
In this article, we’ll discuss the intermolecular forces that prevail within a CCl4 molecule.
What are the intermolecular forces present in CCl4? CCl4 only has London dispersion forces as intermolecular forces that keep its molecules together. Although the C-Cl bonds are polar, there is no dipole-dipole moment induced in a CCl4 molecule. The geometry of the CCl4 molecule is symmetrical ie; tetrahedral, the dipole bonds cancel each other out due to their equal and opposite strength.
The two dipole bonds of C-Cl in front and behind the surface result in an equal and opposite force that cancels out each other. Only the London dispersion forces exist in a CCl4 molecule.
Let us study the intermolecular forces of CCl4 in depth.
What are the Intermolecular Forces of Attraction?
Intermolecular forces of attraction, also known as secondary forces, are the type of forces that facilitate the interaction between molecules.
These forces act between atoms or other particles like ions of a molecule. Intermolecular forces are weaker than intramolecular forces. Intramolecular forces are the ones that hold a molecule together, for instance, covalent bonds.
Intermolecular Forces of CCl4 Molecule
As we discussed earlier, the dipole bonds are canceled out in a CCl4 molecule.
Hence, the only intermolecular force that prevails is the London dispersion force which is a subunit of van der Waals force. These are the weakest forces and have a temporary effect on the molecule.
When any two atoms come adjacent to each other so that their electrons occupy particular locations. This makes the atoms form a temporary dipole and London dispersion forces are induced within the molecule.
These forces are also known as fluctuating dipole-induced dipole attraction.
At low temperatures, London dispersion forces result in non-polar molecules condensing into liquids from gases and freezing into solids from liquids.
Electrons are in constant motion, hence their distribution around the nucleus is uneven. This causes an atom or the entire molecule to establish a temporary dipole.
When a second atom or molecule gets close to this induced one, there is an electrostatic force developed that causes attraction between the two atoms or molecules.
Factors that affect the Strength of London Dispersion Forces
The effect and longevity of London dispersion forces pivot two crucial factors. They are as follows:
Size of the Molecule
London dispersion forces exist within both polar and non-polar molecules. However, the strength of these forces is directly proportional to the size and weight of the atom or molecule.
Hence, larger and heavier atoms or molecules tend to have stronger London dispersion forces than smaller ones.
This is because, in a large molecule, the valence electrons in the outermost shell are farther away from the nucleus than the smaller one. They are loosely bound and can easily be released to form a temporary dipole.
London dispersion forces are stronger in polarized molecules. Polarized molecules are the ones whose electron distribution around an atom can be easily distorted.
The Shape of the Molecule
The shape and structure of the molecule also impact the strength of London dispersion forces.
At room temperature, for instance, neopentane (C5H12) is a gas while n-pentane (C5H12) is a liquid. This is because the London dispersion forces that exist within the n-pentane molecule are stronger than those of neopentane despite them having the same molecular weight.
The cylindrical shape of n-pentane permits its atoms to come in contact with each other to form temporary dipoles. While the spherical shape of neopentane restricts this development.
Importance of Intermolecular Forces of Attraction
Intermolecular forces of attraction hold prominence because they impact the biological, physical, and chemical properties of a molecule.
The reactivity, melting point, boiling point, freezing point, and solubility of a molecule gets influenced due to its intermolecular forces of attraction.
As the strength of intermolecular forces increases, more energy will be required to separate the molecules.
Hence, with an increase in the intermolecular forces of attraction, we witness an increase in the boiling and melting points of the molecule.
Molecules with a strong intermolecular force of attraction will have a low vapor pressure, higher surface tension, and higher viscosity.
Bonding in CCl4
In a CCl4 molecule, we witness 4 covalent bonds. There are 4 carbon atoms and 1 chlorine atom. Each of these atoms completes its octet through electron sharing.
Also, the electronegativity is relatively low between carbon and chlorine atoms, carbon is 2.5 while chlorine is 3.0.
In a carbon tetrachloride molecule, bonding takes place due to hybridization.
Hybridization revolves around mixing two atomic orbitals which result in the formation of a new hybridized orbital. This newly formed orbital will have a different size and shape than its precursor orbitals.
Carbon is the central atom in a CCl4 molecule. Its electronic configuration is 1s2, 2s2, 2p2.
As you can see, there is an availability of two unpaired electrons. An electron from the 2s orbital jumps into the 2p orbital and modifies the electronic configuration of carbon to 1s2, 2s1, 2p3.
This modification helps us acquire 4 unpaired electrons. The 2s and 2p orbitals combine and form four sp3 hybridized orbitals.
The electronic configuration of chlorine is 1s2, 2s2, 2p6, 3s2, 3p5. It requires one atom to attain a stable state. We have 4 chlorine atoms.
The central carbon atom forms a one sigma bond with each chlorine atom. We get four sigma bonds with sp3 hybridization of each bond.
CCl4 is a tetrahedral molecule.
Is CCl4 a Solid or a Liquid?
CCl4, at room temperature, is a liquid. However, it evaporates easily and forms gas.
CCl4 comes with a sweet odor and is not flammable and dissolves sparingly in water.
Is CCl4 Polar or Non-polar?
The presence of a net dipole moment decides the polarity of a molecule.
In a CCl4 molecule, we witness only C-Cl bonding. The electronegativity of carbon is 2.5 while that of chlorine is 3.0. Hence, the difference in their electronegativity turns out to be 0.5 which is quite negligible.
However, C-Cl bonds are still considered slightly polar. The vector sum of dipole moments for all four C-Cl bonds turns out to be zero.
Therefore, carbon tetrachloride is a non-polar molecule since it’s a symmetric compound.
Which has Stronger Intermolecular Force: CCl4 or CH4?
The total number of electrons present in a CCl4 molecule is 32, while that in a CH4 molecule is 8.
The boiling point of CCl4 is 76.72 degrees while that of methane is -161.6 degrees. CCl4 has a much higher boiling point than that methane.
At room temperature, CCl4 is a liquid while CH4 is a gas. This is because the intermolecular forces in a CCl4 molecule are stronger due to the presence of more electrons than methane.
The London dispersion forces among CCl4 molecules are stronger than among CH4 molecules.
A higher boiling or freezing point proves that the intermolecular forces are stronger in that particular molecule.
Uses of CCl4
CCl4 is used to manufacture bulk quantities of propellants for aerosol cans, refrigerants, oil solvents, rubber waxes, varnishes, and resins.
It is also used as a dry cleaning agent.
Carbon tetrachloride is used to reveal stamp watermarks without causing any damage to the stamp.
It is also used as an integral part to produce lava lamps.
What is the effect of intermolecular forces of attraction on the boiling point of a substance?
The stronger the intermolecular forces of attraction, the harder it will be to separate the liquid molecules and permit them to convert into vapor. Hence, intermolecular forces increase the boiling point of a substance.
What is the effect of intermolecular forces of attraction on the melting point of a substance?
The melting point of a substance pivots on the amount of energy required to overcome the intermolecular forces and break the bonds.
Hence, intermolecular forces of attraction increase the melting point of a substance.
Which force of attraction is stronger: intermolecular or intramolecular?
Intramolecular forces of attraction are stronger than intermolecular ones. This is because intramolecular forces exist between the atoms of the same molecule. They hold the molecule structure together.
However, intermolecular forces are mere attractions that take place between molecules held in close proximity to each other. The bond breaks when the proximity is lost.
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Carbon tetrachloride (CCl4) is a tetrahedral and non-polar molecule. Its C-Cl dipole bonds cancel each other out. Hence, the only intermolecular force of attraction observed is the London dispersion force.
These forces are a result of molecules held close to each other with sufficient space to develop a temporary dipole.
However, the impact of London dispersion forces relies upon the size and shape of the molecule.