Q30. - Organic Chemistry

Question

Question: The unmistakable odor of a freshly cut cucumber is largely due to cucumber aldehyde. (a) How many ${\mathbf{sp}}^{\mathbf{2}}$ hybridized carbon atoms does cucumber aldehyde contain? (b) What is the hybridization of the O atom? (c) What orbitals are used to form the carbon-oxygen double bond? (d) How many $\mathbf{\sigma }$ bonds does cucumber aldehyde contain? (e) How many   bonds does it contain?

                                  

Step-by-Step Solution

Answer

Answer

1. The count of ${\mathrm{sp}}^2$  hybridized carbon atoms is five in cucumber aldehyde.
2. The hybridization of the O atom is ${\mathrm{sp}}^2$ .
3. The  ${\mathrm{sp}}^2-{\mathrm{sp}}^2$ hybrid orbitals are used in the formation of carbon-oxygen (C=O) double bonds.
4. In cucumber aldehyde, the total count of  $\sigma$ bonds is 22.
5. In cucumber aldehyde, the total count of $\mathrm{\pi }$bonds is 3.

 

Step-by-Step Solution Step 1: Hybridization

The phenomenon of mixing of atomic orbitals to form/generate hybrid orbitals is called hybridization.

 

An atom is said to be  ${\mathrm{sp}}^2$ hybridized if three orbitals are participating in hybridization, that is, the atom is bonded to three other atoms.

 

Step 2: sp 2 hybridized carbon atoms in cucumber aldehyde

All the carbon atoms that contain a double bond are ${\mathrm{sp}}^2$hybridized as they are attached with three other atoms.

                                         

                                                 Structure of cucumber aldehyde

Therefore, there are five${\mathrm{sp}}^2$hybridized carbon atoms in cucumber aldehyde.

 

Step 3: Hybridization of the oxygen atom

 

The hybridization of an oxygen atom that forms only one pi bond is ${\mathrm{sp}}^2$. The oxygen atom present in cucumber aldehyde forms only one pi bond with the carbon atom. Hence, it is ${\mathrm{sp}}^2$hybridized.

Step 4: The orbitals used to form the carbon-oxygen double bond

The carbon and oxygen atoms that form a double bond with each other are both  ${\mathrm{sp}}^2$ hybridized. Hence, the carbon-oxygen double bond is formed by the overlap of  ${\mathrm{sp}}^2-{\mathrm{sp}}^2$ hybrid orbitals.

 

Step 5: Sigma and pi bonds in cucumber aldehyde

Every single bond comprises a sigma bond. Each double bond comprises a sigma and a pi bond.  

The total count of $\mathrm{\sigma }$ bonds in cucumber aldehyde is 22.

The total count of $\mathrm{\pi }$ bonds in cucumber aldehyde is 3.