Q66. - Organic Chemistry

Question

Question: Ketene, ${\mathbf{CH}}_{\mathbf{2}}\mathbf{=}\mathbf{C}\mathbf{=}\mathbf{O}$ , is an unusual organic molecule that has a single carbon atom doubly bonded to two different atoms. Determine the hybridization of both C and the O in ketene. Then, draw a diagram showing what orbitals are used to form each bond (similar to Figures 1.10 and 1.11).

Step-by-Step Solution

Answer

Answer

The carbon atom [1] is   hybridized, carbon [2] is ${\mathrm{sp}}^2$ -hybridized, and the oxygen atom is ${\mathrm{sp}}^2$ hybridized

                                                      

                                                                     Ketene molecule

Following are the diagrams showing the formation of bonds:

                                         

   

                                               

                                                

Step-by-Step Solution Step 1: Structure of the ketene molecule

Ketene molecule has the following structure:

                                           

                                                       Ketene molecule

 

 

Step 2: Hybridization of carbon and oxygen atoms

The two carbon atoms in the ketene are labeled as carbon [1] and carbon [2], as shown in the following structure:

                                                     

                                                                 Ketene molecule

 

Carbon [1] has three groups attached to it. It forms a double bond with carbon [2]. The hybridization of carbon [1] is ${\mathrm{sp}}^2$ .

Carbon [2] forms a double bond with the oxygen atom and the carbon atom. It has two groups attached to it. The hybridization of carbon [2] is $\mathrm{sp}$-hybridization

Step 3: Diagram showing the formation of sigma bonds

The sigma bond is generated by the overlap of the bonding orbitals along/through the internuclear axis. 

In the ketene molecule, the sigma bonds are shown in the following diagram:

                                                 

                                              Diagram showing the sigma bonds

Carbon [1] is  -${\mathrm{sp}}^2$hybridized. It has three  -${\mathrm{sp}}^2$hybrid orbitals. It uses two hybrid orbitals to form a sigma bond with the two hydrogen atoms. The hydrogen atom uses its 1s orbital to form a sigma bond with carbon atoms.

 

Carbon [2] is $\mathrm{sp}$-hybridized. It uses one of its $\mathrm{sp}$-hybrid orbitals to form a sigma bond with an oxygen atom. The other $\mathrm{sp}$-hybrid orbital is used to form a sigma bond with carbon [1].

 

The oxygen atom is ${\mathrm{sp}}^{\mathit{2}}$-hybridized. It uses one of its ${\mathrm{sp}}^{\mathit{2}}$ -hybrid orbitals to form a sigma bond with the carbon atom. The other two hybrid orbitals have a lone pair of electrons each, as shown in the diagram.

 

Carbon [1] uses ${\mathbf{sp}}^{\mathbf{2}}$ -hybrid orbital and [2] uses its $\mathbf{sp}$-hybrid orbital to form a C-C sigma bond.

Step 4: Diagram showing the formation of bonds

A $\mathbf{\pi }$bond is formed by the sidewise/lateral overlap of the unhybridized orbitals. The double bond consists of one sigma bond and one   bond. The triple bond consists of one sigma bond and two   bonds.

                                             

                                     The diagram showing the $\mathrm{\pi }$ bonds

 

Carbon [1] is forming a   bond with carbon [2]. The unhybridized p orbital of carbon [1]carbon [1] overlaps sidewise with the unhybridized p orbital of carbon [2].

Carbon [2] consists of two unhybridized p orbitals. It forms a double bond with both carbon and oxygen atoms. One of the unhybridized p orbitals of carbon [2] overlaps sideways to form a $\mathrm{\pi }$ bond with carbon [1].

It forms another   bond with the oxygen atom. The other unhybridized p orbital overlaps with the unhybridized p orbital of the oxygen atom.