Molecular Geometry, Hybridization, and Polarity of COCl2 Lewis Structure

COCl2 is a chemical molecule that is also known as phosgene.

Phosgene, also known as carbonyl chloride, is a colourless gaseous chemical with a molecular weight of 98.92 gram/mol.

It has a suffocating odour and is non-flammable in nature. Its boiling point (b.p.) is around 8.3 0C. Phosgene is also known as acyl chloride. The following reaction depicts the process of COCl2 production from CO and Cl2:

CO + Cl2 —> COCl2 (exothermic reaction, temp between 50-150 degree C)

The catalyst in this case is activated porous carbon.

Carbonyl chloride is used in a variety of industrial and scientific settings.

It’s used to make herbicide precursors, as well as medications and pesticides. COCl2 is also required for the synthesis of some polycarbonate compounds, which are used in the manufacture of eye lenses and other appliances.

COCl2 is also employed in the separation of ore.

Because it is exceedingly deadly and hazardous, it must be handled with caution and using safety procedures.

Lewis Structure of COCl2

In this article, we’ll look at phosgene’s chemical bonding properties.

To comprehend it in depth, we must first understand the concept of Lewis Structure.

Lewis Structure is a two-dimensional diagrammatic representation of a molecule’s electron configuration (note: valence electrons). It provides us with a graphical representation of the process, complete with electron-dot notations, so that we can grasp it quickly.

The first step is to determine the valence or outermost shell electrons in a COCl2 molecule.

C belongs to group 14 and has an atomic number of 6 according to the periodic table. As a result, it has four valence electrons.

Oxygen is a member of the chalcogen family’s group 16 (or group 6) and has an atomic number of 8. It has 6 electrons in its valence shell.

Because it belongs to group 17, chlorine has seven valence electrons.

One C, one O, and one Cl atom make up the COCl2 molecule.

4 + 6 + 7*2 = 10 + 14 = 24 is the total amount of valence electrons.

Step 2: Next, we must identify the element that will occupy the central atom’s position.

Because carbon is the least electronegative of the three elements, it will serve as the core atom, providing greater stability and electron density spread.

The chlorine and oxygen atoms will occupy the locations of the atoms in the vicinity.

(We’ll go over electronegativity in greater depth in the subsection on Polarity.)

Step 3: We’ll draw the skeleton diagram of the molecule in question.

Step 2 will be followed to position the atoms. This is how the skeleton will appear:

Step 4: Valence electrons will be positioned around the atoms in the molecule using dot notations, according to the electron-dot structure concept.

We’ll put them in order based on the bond creation and the total number of bonds.

Step 5: Before we can ensure that our Lewis Structure diagram is right, we must first verify two ideas.

The first is the concept of octet fulfilment.

The octet rule states that elements in groups 1 to 17 have a tendency to achieve the octet fulfilment state of the noble gas elements such as Ne, Ar, and so on.

The elements Cl and O have both achieved the octet configurations in the COCl2 diagram. However, the core C atom has not yet reached an octet. Its atom is surrounded by only six electrons.

The electronegativity values of Cl and O will now be compared. Because O has a lower value, we’ll take two valence electrons from it and share them with Carbon.

This is how the diagram will look:

As can be seen, each of the four atoms now has eight valence electrons surrounding it. All of the elements’ atoms, carbon, chlorine, and oxygen, have achieved the essential octet configurations.

Step 6: Now let’s look at the following concept: formal charge.

If we believe that the electrons inside a molecule will be shared evenly among the bound atoms that form a molecular structure, the formal charge is ascribed to an atomic element.

Charge in writing

Each Cl atom has a formal charge of 7 – 12*2 – 6 = 0.

O atom formal charge = 6 – 12*4 – 4 = 0.

C atom formal charge = 4 – 12*8 – 0 = 0.

Within the phosgene molecular structure that we have drawn, the values suggest that all of the elements have the lowest possible formal charges.

As a result, this is the accurate representation of COCl2 in Lewis Structure.

A single bond is formed when two atoms share a single electron pair, whereas a double bond is formed when two atoms share two electron pairs, or four electrons.

Molecular Geometry of COCl2

In this section, we’ll study about Molecular Geometry, which is a chemical term. The orientation of atomic atoms within a molecule structural composition is determined by the 3-dimensional atomic arrangement.

To explain the 3D molecular geometry of molecules, we employ the Valence Shell Electron Pair Repulsion (VSEPR) model.

Electrons are subatomic particles that make up the nuclei’s negatively charged cloud environment. They resist each other because they are like changes. To decrease these repulsive interactions, constituent atoms of a molecule are separated by a large distance.

Now we’ll apply this idea to deduce COCl2’s 3D molecule shape.

The core atom of COCl2 is carbon. It is surrounded by three atoms: one oxygen atom, two chlorine atoms, and no lone pair. As a result, the core atom is surrounded by three electron-rich areas.

AXnEx: according to VSEPR notation

The letter ‘A’ stands for the centre atom.

‘X’ denotes the atoms in the immediate vicinity, and

The unbonded or lone pair on the centre atom is represented by the letter ‘E.’

AX3E0 is the VSEPR designation for a phosgene molecule.

We’ll now examine the VSEPR chart to determine the shape:

COCl2 has a trigonal planar 3D geometry, as we can see.

C-Cl bonds have a bond angle of 111.8 degrees (less than 120 degrees due to the C=O electron density, which lessens the bond angle).

Hybridization of COCl2

One of the most important principles in chemical bonding is orbital hybridization.

While an orbit refers to a specific path that an electron follows, an orbital is a quantum mechanics word that indicates the likelihood of an electron’s presence in a given region.

Hybridization is concerned with atomic orbitals in this case (AOs). The Aufbau principle and the Madelung rule are used to organise AOs in order of increasing energy. The following is the order in which orbitals are filled:

1st 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd 2nd

When AOs of similar energy levels collide and fuse, we get hybridised orbitals with different energy levels and forms than the atomic orbitals involved in the process. As an example,

Two sp orbitals are formed by combining a s and a p orbital.

Three sp2 orbitals are formed from a s and two p orbitals.

Four sp3 orbitals result from a s and three p orbitals, and so on.

To understand chemical bonding in molecules, we employ the hybridization model.

Let’s investigate the hybridization of a phosgene molecule presently.

The electronic configuration of the core atom, C, is 1s2 2s2 2p2 (atomic number of C is 6), while the electronic configuration of Chlorine is 1s2 2s2 2p6 3s2 3p5 (atomic number = 17).

O has the following electrical configuration: 1s2 2s2 2p4 (atomic number = 8)

C’s electrical configuration is as follows:

The ground state is depicted in the first diagram.

After then, one electron from the 2s orbital moves to the vacant 2p orbital.

Three sp2 hybrid orbitals result from hybridization between the s and two p orbitals. As a result, the remaining p orbital is unhybridized.

A single bond creation is represented by the sigma bond ().

There will be both and pairs if there is a double bond.

Two sp2 hybrid orbitals of C bond with the 3p orbital of Cl in the two C-Cl bonds, which are sigma bound.

One bond from C’s sp2 hybrid orbital overlaps with O’s 2p orbital, and one bond from C’s sp2 hybrid orbital overlaps with O’s 2p orbital.

This explains why carbon in phosgene is sp2 hybridised.

Hybridization can also be calculated using the steric number.

3 + 0 = 3 Steric Number

sp2 = hybridization

Polarity of COCl2

Now we’ll talk about the concept of polarity.

The Pauling Electronegativity chart is shown here.

Carbon has an electronegativity of 2.55, O has a value of 3.44, and Cl has a value of 3.16.

When the electronegativity difference between two atoms in a bond exceeds 0.4-0.5, the bond is considered to be polar.

As a result, the C=O bond (difference = 0.89) and the C-Cl bond (difference = 0.61) are both polar. There are two ends to the bonds: one positive and one negative. Carbon has a partial + and Cl has a partial – in C-Cl bonds.

The COCl2 molecule is also not symmetrical or linear. Electric dipoles do not cancel each other out. As a result, the resulting molecule is polar.

Conclusion

COCl2, the phosgene molecule, has been discussed in this article.

Lewis Structure, VSEPR theory, which can predict Molecular Geometry, Orbital Hybridization, and Polarity, are among the subjects covered.

Good luck with your studies!

Read more: Is NaCl Covalent or Ionic?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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