Q1-12P - Organic Chemistry (Mcmurry)

Question

Following is a molecular model of aspirin (acetylsalicylic acid). Identify the hybridization of the orbitals on each carbon atom in aspirin, and tell which atoms have lone pairs of electrons (gray 5 C, pink 5 O, ivory 5 H).   

                                 
 Aspirin (acetylsalicylic acid)

Step-by-Step Solution

Answer

The carbon atom of aspirin shows ${\mathrm{sp}}^3$ and ${\mathrm{sp}}^2$ hybridization. Oxygen atoms in the Aspirin molecule have lone pair of electrons.

Step 1: Definition of hybridization and Lone pair

Hybridization is the mixing and recasting of the atomic orbitals to form new orbitals of equal energy. 

The lone pair is nothing but the unshared pair of electrons.

Step 2: Hybridization of each carbon atom of aspirin

In an easy way, we can say if carbon double bond carbon is present then carbon-atom is ${\mathrm{sp}}^2$ hybridized and if carbon single bond carbon then that carbon is ${\mathrm{sp}}^3$ hybridized. So here all the carbon which is indicated by ‘b’ are ${\mathrm{sp}}^2$ hybridize while a carbon atom which is indicated by ‘a’ is ${\mathrm{sp}}^3$.

Step 3: Atoms have lone pair of electron

As the valance of the carbon atom is completed as it forms four bonds with another carbon atom so it does not contain a lone pair of electrons. All the oxygen atoms in the aspirin structure contain lone pair of electrons. Each oxygen atom contains two lone pairs of electrons.