Trichloromethane, or chloroform, is a volatile organic molecule with one carbon atom covalently bound to three chlorine atoms and one hydrogen atom.
It’s a white liquid with a distinct smell.
It is made at a laboratory scale by chlorinating ethanol. As a chlorinating agent, bleaching powder is frequently employed.
It was previously used as an anaesthetic for medical treatments. It is now widely utilised as a solvent for organic molecules, as well as in the manufacture of polymeric materials and refrigerants.
It’s an industrial chemical that can irritate the eyes. It is non-combustible.
Chloroform is generally kept in dark-colored bottles. If maintained in light-colored bottles, it will oxidise and produce phosgene (a toxic gas).
In this article, we’ll learn about the notion and technique for determining a molecule’s Lewis structure, geometry, hybridization, and polarity.
Lewis Structure of CHCl3
The Lewis Structure depicts the arrangement of valence shell electrons in a molecule in a straightforward way. It informs us that there is a relationship between atoms, but it does not specify the type of bond.
Valence electrons are represented by dots in the Lewis structure, while two bonding electrons between two atoms are represented by a line.
For verification of the so-drawn Lewis structure, the octet rule and formal charges must be satisfied.
The octet rule states that noble gases are stable and have 8 electrons in their valence shell.
To achieve stability, main group elements tend to have an electrical configuration similar to that of a noble gas (8 electrons in the valence shell).
To attain octet configuration, the atom prefers to lose or gain electrons if there are more or less than 8 electrons.
In a Lewis structure, all atoms should have eight electrons around them.
Formal Fee: This is merely a theoretical concept, not a real charge.
It’s used to figure out how a polyatomic molecule’s individual atoms are charged.
The net charge must equal the total of all formal charges on all atoms.
It is calculated by subtracting the number of electrons assigned to each atom in the Lewis structure from the number of valence electrons in the free state of the atoms.
Drawing the Lewis Structure of CHCl3 in Steps
Step 1: Determine the molecule’s total number of valence electrons.
It’s calculated by summing up all of the atoms’ valence electrons.
Atomic Number Atomic Number Atomic Number Atomic Number Atomic Number Atomic Number Atom
According to group number, valence electrons
Configuration of electronic devices (E.C.)
E.C.’s Valence Shell
E.C.’s valence electrons
C 6 14 4 1s2 2s2 2p2 n=2
4
1 1 1 1s1 n=1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Cl 17 17 7 (three)
n=3 1s2 2s2 2p6 3s2 3p5
7
Total number of electrons in the valence shell = 4 + 1 + (7*3) = 26
The number of valence shell electrons can be used to draw the Lewis structure for H, C, and Cl.
Step 2: Pick the atom in the centre.
The core atom is chosen to provide stability to the entire molecule while also facilitating electron density spread.
Because it must share the electron density with the surrounding atoms, the centre atom should not be particularly electronegative like Cl.
The electron density of chlorine will not be shared with other elements. H is the smallest of the two atoms and is not suited for use as a central atom.
As a result, the chloroform atom’s core atom is C.
Step 3: Draw the molecule’s skeletal diagram.
Step 4: Arrange the valence electrons around the atoms individually.
The electrons in the entire valence shell of the molecules are arranged in the preferred bond formation.
Step 5: Form bonds to complete the octet of atoms.
The octet arrangement of chlorine and carbon atoms has been achieved.
To create a fully filled structure, H has only one electron, which is shared with one electron of C. The greatest number of electrons in a 1 is two.
Step 6: Determine all atoms’ formal charges.
Although the molecule’s net charge is zero, this does not mean that the formal charge on all atoms is also zero.
The formal charge is determined using the following formula:
Atom
A free atom’s total number of valence electrons
Formal Charge*0.5 Total amount of lone pairs (Total number of bonding electrons)
C 4 0 8*0.5=4
4-0-4=0
H 1 0 2*0.5=1
1-0-1=0
Cl1 7 3 8*0.5=4
7-3-4=0
Cl2 7 3 8*0.5=4
7-3-4=0
Cl3 7 3 8*0.5=4
7-3-4=0
The first, second, and third chlorine atoms are indicated by the subscript in Cl.
The lewis structure is correct in this form. This video can be used to gain a better understanding.
Geometry of CHCl3
One of Lewis structure’s numerous flaws is that it can’t inform us about a covalent compound’s molecular geometry. The VSEPR theory proves useful in resolving this flaw.
The representation of all atoms and bonds of a molecule in space is known as molecular geometry.
This flaw is overcome by the VSEPR hypothesis (Valence Shell electron pair repulsion theory).
The VSEPR theory states that
• Atoms in a molecule’s valence shell electron pairs resist one other, causing instability.
• Repulsions must be reduced in order for the arrangement to be stable.
• Electrons align themselves with the least amount of repulsion and the greatest distance between them.
• The molecule geometry is determined by the stable arrangement of atoms’ valence electron pairs.
Bonding pairs of electrons (bp) are electrons in the Valence Shell that are involved in bonding.
Lone pairs of electrons are valence shell electrons that are not involved in bonding (lp).
VSEPR Methods for Predicting Molecular Geometry
Count the electrons in the valence shell of the centre atom (N).
The core atom (C) in CHCl3 has a total of four valence shell electrons.
• To get A, add one electron to N for each surrounding atom. For a negative charge on a molecule, the electrons are added to A, and for a positive charge on a molecule, they are withdrawn.
Because C has four surrounding atoms in chloroform, A=4+ (1*4)+0=8.
• Multiply A by 2 to get the total number of domains or electron pairs.
Total domains are 4 (8/2=4) in this case.
• If total domains=number of surrounding atoms, the central atom has no lone pair.
Thus, the overall number of electron pairs in chloroform is equal to the total number of bonding electron pairs, which is 4, and the lone pair is zero.
• Using the table below, we can predict the shape.
As a result, CHCl3 has a tetrahedral geometry and form.
Hybridization using CHCl3
Hybridization is a term that describes the geometrical shape and bonding of polyatomic molecules.
An orbital is a three-dimensional region around the nucleus where the chances of finding an electron are greatest.
The mixing of pure atomic orbitals to generate hybrid atomic orbitals is known as hybridization. If the pure atomic orbitals are of similar form and energy, this mixing is possible.
2s and one 2p, for example, can generate sp hybrid orbitals, while 2s and 5d can’t. In addition, one 2s and three 2p orbitals are combined in C (carbon atom) to generate four comparable sp3 hybrid orbitals.
The chloroform molecule’s core atom is C.
C’s electrical ground state configuration is 1s2 2s2 2p2. In hybridization, only valence orbitals are utilised.
One 2s electron is promoted to the 2p orbital in the excited state. These four orbitals (one 2s and three 2p) are now hybridised to produce four sp3 orbitals, which will make bonds with the atoms in the vicinity.
There are four surrounding atoms in CHCl3. With one sp3 hybrid orbital, each atom creates a bond.
Hybridized orbitals of CH3Cl
A sigma bond with sp3 hybrid orbitals is formed by three Cl atoms and one H atom. As a result, CHCl3 is sp3 hybridised.
The secret of determining the type of hybridization.
In the last step of VSEPR theory, we estimated the total electron pairs. It was found to be 4 for CHCl3.
We can anticipate hybridization using total electron pairs or steric numbers from the table below.
The CHCl3 molecule’s bond angle is roughly 109.5°, and hybridization is sp3.
Polarity of CHCl3
A compound’s polarity is determined by the following factors:
• Moment of dipole
• The difference between two atoms’ electronegativity
• Aesthetics, symmetry, and geometry
• Separation of charges
If the electronegativity of the two atoms making the bond is different, the bond is polar (dipole moment is not zero).
In chloroform, there are two types of bonds: C-Cl and C-H. Both are polar, with electronegativity differences of 0.61 (3.16.55) and 0.35 (2.55-2.2), respectively.
The presence of polar bonds does not guarantee the presence of a polar molecule. All bonds in a symmetrical molecule are of the same kind, thus dipole moments frequently cancel out.
The dipole moment vector for C-Cl bonds is directed from the C to the Cl atom. The three bond moment vectors for C-Cl are all pointing downward.
The dipole moment vector in the C-H bond is oriented from the H atom to the C atom. The direction of the C-H bond moment vector is upward.
Three C-Cl bond vectors have a larger magnitude than the C-H bond vector, and the net dipole moment is downward.
As a result, the molecule has polar properties.
Conclusion
Chloroform is a clear liquid with a distinctive odour.
In chloroform, the C- atom makes one covalent connection with each Cl- atom and another with the H-atom.
CHCl3 has a tetrahedral geometry and form.
It is a non-polar molecule with an sp3 hybridization.
I hope you enjoyed learning about chloroform chemistry. If you have any questions, please post them in the comments section. I will gladly respond to your questions.
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