Lewis Structure, Molecular Geometry, Hybridization, Polarity, and the MO Diagram for the compound C2H6

Ethane, often known as C2H6, is a saturated open-chain hydrocarbon that belongs to the alkane family. A hydrocarbon is an organic substance made up entirely of carbon and hydrogen. Hydrocarbons with single carbon-hydrogen and carbon-carbon bonds are known as saturated hydrocarbons.

Alkane (open chain of carbon atoms) and cycloalkane (closed chain of carbon atoms) are two types of saturated hydrocarbons (closed chain of carbon atoms). CH3-CH3 is another way to write ethane.

At ordinary temperature and pressure, ethane is a colourless and odourless gas. Ethane has a melting point of -182.8 °C and a boiling point of -89 °C. Because ethane has a flashpoint of -135 °C, its fumes are easily ignited by an ignition source.

Ethane has a molar mass of 30.07 g/mol. In the industrial world, ethane is made from natural gas and petroleum. It can also be made in the lab from ethene, ethyl chloride, and sodium acetate. The following are some ethane preparation methods:

CH2   =    CH2 + H2    —–Pt/Pd/Ni——>     CH3 − CH3

CH3 − CH2Cl + H2     —— Zn/H+ —–> CH3 − CH3    +     HCl

2CH3Cl     +    2Na      ——Dry ether——> CH3 − CH3    +   2 NaCl

CH2   =    CH2 + H2    —–Pt/Pd/Ni——>     CH3 − CH3

CH3 − CH2Cl + H2     —— Zn/H+ —–> CH3 − CH3    +     HCl

2CH3Cl     +    2Na      ——Dry ether——> CH3 − CH3    +   2 NaCl

Let’s go over some basic ethane principles like Lewis structure, polarity, carbon atom hybridization, and the Molecular orbital (MO) diagram to better comprehend its chemical bonding in terms of molecular orbitals.

Lewis Structure of C2H6

Lewis structure is a two-dimensional depiction of a compound in which only the valence shell electrons of the atoms in the molecule are represented.

It is based on the octet rule, which states that every atom, with the exception of Hydrogen and Helium, tends to fulfil its octet (8 electrons) by gaining or losing electrons.

Let’s have a look at the Lewis structure of ethane one step at a time.

Step 1: Determine the molecule’s total number of valence electrons.

Carbon (1s22s22p2) and hydrogen (1s1) have valence electrons of 4 and 1, respectively. Because there are two carbon atoms in ethane and six hydrogen atoms, the total number of valence electrons is (2 X 4) + (1 X 6) = 14.

Step 2: Make a sketch of the Lewis structure:

A carbon atom possesses four valence electrons and requires four more for its octet to be complete. By sharing electrons, it creates four bonds, one with nearby carbon atoms and three with three hydrogen atoms.

Ethane’s Lewis structure is as follows:

In the Lewis structure of ethane, we can count the total number of valance electrons, which is 14.

The total number of electrons surrounding each carbon atom is 8, indicating that the octet has been completed. Duplet production occurs when each hydrogen atom is surrounded by two electrons.

If we look closely, we can see that all 14 valance electrons were utilised to make the link. As a result, there are no lone pairs of electrons on any ethane atom.

Let us now transition from a 2D to a 3D representation of the molecule, i.e. ethane molecular geometry.

C2H6 Molecular Geometry

The valence shell electron pair repulsion (VSEPR) theory determines a compound’s molecular shape.

According to this hypothesis, the amount of bonding electrons and lone pairs of electrons determines the form and geometry of the molecule. Carbon is the core atom in ethane, and it has no lone pair of electrons.

Due to the lack of a lone pair of electrons, the geometry and shape of ethane will remain unchanged. As a result, the following table can be used to forecast the geometry/shape of ethane:

General formulaNumber of bond pairsMolecular shape/geometry
AX1Linear
AX22Linear
AX33Trigonal planar
AX44Tetrahedral
AX55Trigonal bipyramidal
AX66Octahedral

In the Lewis structure, we’ve already seen that carbon, a core atom, forms four bonds: one with the nearest carbon atom and three with hydrogen atoms.

Each carbon atom’s four bond pairs correlate to its tetrahedral geometry/shape, whereas each hydrogen atom’s one bond pair refers to its linear geometry/shape.

As a result, ethane’s three-dimensional structure would be:

The tetrahedral geometry of ethane results in a bond angle of 109.5 degrees (H-C-H or H-C-H). The C-C and C-H bonds have lengths of 153.52 pm and 109.40 pm, respectively.

We go on to the hybridization of carbon atoms in the ethane molecule after analysing the Lewis structure and molecular geometry.

Hybridization of C2H6

Hybridization is the process of combining two or more atomic orbitals of similar energy to generate hybrid orbitals.

In the valence bond theory (VBT), the hybridization term is used to explain the structure, formation, and directional aspects of bonds in polyatomic molecules.

Now we’ll use valence bond theory to figure out how ethane hybridises.

The electrical configuration of C in its ground state is 1s22s22p2, with two unpaired electrons in the p orbital and one pair of electrons in the valence shell’s s orbital.

Carbon, on the other hand, creates four bonds, and paired electrons are not involved in bond formation.

As a result, one of the 2s electrons is excited to the p orbital, and the carbon atom’s excited state electronic configuration is 1s22s12p3.

The overlapping of carbon and hydrogen orbitals provides this excitation energy. Because one 2s orbital and three 2p orbitals have almost the same energy, they combine to generate four sp3 hybrid orbitals with the same energy.

As a result, in ethane, the hybridization of both carbon atoms is sp3 with tetrahedral geometry.

Three of the four sp3 hybrid orbitals will overlap axially with three 1s orbitals of the hydrogen atom, and one will overlap axially with another carbon atom’s sp3 hybrid orbital. Each carbon atom forms four sigma bonds as a result of this reaction.

Ethane’s orbital diagram is as follows:

Polarity of C2H6

On the Pauling scale, C and Hydrogen have electronegativity of 2.6 and 2.2, respectively.

Because the electronegativity difference between a carbon atom and a hydrogen atom is only 0.4, the C-H bond in ethane is nonpolar. It results in the ethane molecule’s nonpolar character.

Polar molecules are dissolved by polar solvents, while nonpolar molecules are dissolved by nonpolar solvents. As a result, ethane is more soluble in toluene and benzene but very little or none in water.

Diagram of the Molecular Orbital (MO) of C2H6

The molecular orbital (MO) diagram of the ethane molecule is drawn using the molecular orbital theory, a quantum mechanical model. It is based on the production of the molecular orbital through the linear combination of atomic orbitals.

Ethane’s molecular orbital diagram would be:

The molecular orbital is made up of atomic orbitals that must be substantially identical in energy and symmetrical around the molecule axis.

Consider ethane as a homonuclear diatomic A2 molecule to understand the MO diagram.

For the sake of clarity, we’ll assume A is the CH3 group and just consider valence shell electrons. Because ethane has a total of 14 valence electrons, each CH3 group will have 7 electrons. These seven electrons can be found in a variety of atomic orbitals, including, and n.

One is bonding and the other is nonbonding as two atomic orbitals combine to generate two molecule orbitals. Three atomic orbitals become three molecular orbitals, and so on.

As a result, the following is how molecular orbitals are formed:

Each CH3 group’s atomic orbitals will result in the development of two molecular orbitals, such as s and s’.

Each CH3 group’s two atomic orbitals will result in the development of four molecular orbitals, such as y, z, and y’, z’.

Each CH3 group’s n atomic orbitals will result in the development of two molecular orbitals, such as x and x′.

After the molecular orbitals have been constructed, electrons are distributed into them using the Aufbau principle, Hund’s rule of maximal multiplicity, and Pauli’s exclusion principle.

As a result, electrons are filled in molecular orbitals in the sequence of increasing energy, for example, s s′ y = z x y′ = z′ x′.

One atomic orbital can hold a maximum of two electrons with opposite spins, according to Pauli’s exclusion principle.

The same can be said for molecular orbitals. Only when all of the degenerate molecular orbitals are singly occupied would electrons couple in the degenerate molecular orbitals.

As a result, the ethane molecule’s electrical configuration for the valence shell electron would be:

(σs)2(σs′)2(πy2 = πz2)(σx)2(πy′2 = πz′2)

Conclusion

Ethane, often known as C2H6, is a saturated hydrocarbon that belongs to the alkane family. It is known as paraffin because it is inert at ambient temperature and pressure. It does, however, exhibit some chemical reactions when certain circumstances are met. The basic notions of the reactant molecule can help you understand the nature of chemical reactions.

We learned how to sketch an ethane molecule’s Lewis structure using the octet rule, and then discovered their molecular geometry, which turned out to be tetrahedral for both carbon atoms.

After that, we talked about ethane’s hybridization and polarity. For a better understanding, we looked at the molecular orbital diagram of ethane by treating the CH3 group as an atom.

In a nutshell, we’ve looked into every facet of ethane bonding.

Please feel free to ask any questions you have about the ethane molecule’s binding properties. Thank you for taking the time to read this article.

Read more: Is Gasoline a Mixture of Homogeneous Components?

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.

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Read More

Recent