Animated Solution for Chemistry - Polymers: Bakelite is obtained from phenol by reacting with

Building a Thermosetting Giant

Have you ever wondered what makes the black handles of your kitchen utensils so resistant to heat? Or why the electrical switches in your house don't melt when a current passes through them? The answer lies in a remarkable synthetic polymer known as Bakelite.

Bakelite holds a special place in the history of chemistry as one of the first fully synthetic plastics. Unlike the plastic water bottles that melt and deform when heated (thermoplastics), Bakelite is a thermosetting polymer. Once it is molded and set into a shape, it forms a rigid, infusible, and insoluble mass that cannot be remelted. But how do we build such a robust material?

Phenol and Formaldehyde

To construct the highly cross-linked 3D network of Bakelite, we need two specific monomers.

The first monomer is Phenol ($C_6{H}_{5}OH$). It consists of a benzene ring attached to a hydroxyl ($-OH$) group. The hydroxyl group makes the benzene ring highly reactive towards electrophilic substitution, particularly at the ortho and para positions.

The second monomer is Formaldehyde ($HCHO$), which is the simplest aldehyde. In this reaction, formaldehyde acts as the crucial cross-linking agent that bridges multiple phenol molecules together.

The magic happens when phenol and formaldehyde are mixed in the presence of either an acidic ($H^{+}$) or an alkaline ($O{H}^{-}$) catalyst.

Initially, formaldehyde attacks the ortho and para positions of the phenol ring, forming ortho- and para-hydroxymethylphenols. As the reaction proceeds, these intermediate molecules undergo condensation—meaning they link together while eliminating small molecules like water ($H_{2}O$).

First, they form a linear polymer called Novolac, which is often used in paints. However, upon further heating with more formaldehyde, extensive cross-linking occurs between the linear chains. This massive, interconnected web of molecules is what we call Bakelite.

Returning to our question, the polymer Bakelite is synthesized by reacting phenol with formaldehyde. Looking at the chemical formulas provided in the options, formaldehyde is represented as $HCHO$. Therefore, the correct choice is undeniably option (d). Understanding the monomers not only helps in solving such direct questions but also gives you an appreciation for the molecular architecture of everyday materials.