Problem 26 - A Complete Resource Book in Chemistry for JEE Main

Question

(Me) \(_{2} \mathrm{SiCl}_{2}\) on hydrolysis will produce (a) \((\mathrm{Me})_{2} \mathrm{Si}(\mathrm{OH})_{2}\) (b) \((\mathrm{Me})_{2} \mathrm{Si}=\mathrm{O}\) (c) \(-\left[-\mathrm{O}-(\mathrm{Me})_{2} \mathrm{SI}-\mathrm{O}-\right]_{\mathrm{n}}-\) (d) \(\mathrm{Me}_{2} \mathrm{SiCl}(\mathrm{OH})\)

Step-by-Step Solution

Answer

The correct answer is (c), the siloxane polymer.

Step 1: Understanding the Reactant

The given compound is dimethyl dichlorosilane, (Me)₂SiCl₂. Here, Me represents a methyl group (CH₃). The silicon atom (Si) is bonded to two methyl groups (Me) and two chlorine atoms (Cl).

Step 2: Concept of Hydrolysis

Hydrolysis involves the reaction of a compound with water, leading to the breaking of bonds and the formation of new substances. For silanes, like (Me)₂SiCl₂, hydrolysis typically involves the replacement of chlorine atoms by hydroxyl groups (OH).

Step 3: Reaction of Hydrolysis

Upon hydrolysis of (Me)₂SiCl₂, the two chlorine atoms are replaced by two hydroxyl groups. The intermediate product will be (Me)₂Si(OH)₂, which is option (a).

Step 4: Further Condensation Possibility

The initial hydrolysis product, (Me)₂Si(OH)₂, can undergo further condensation reactions where water is eliminated, forming siloxane linkages -O-(Me)₂Si-O-. This results in a polymeric structure, corresponding to option (c).

Step 5: Identifying the Correct Answer

Multiple products can form considering different stages of the reaction. The direct product of hydrolysis is (Me)₂Si(OH)₂. However, further polymerization leads to a siloxane polymer as the stable form, represented by -[-O-(Me)₂Si-O-]₀-, option (c). Therefore, the polymer structure is correct given full reaction.

Key Concepts

Dimethyl dichlorosilane

Dimethyl dichlorosilane, commonly written as (Me)₂SiCl₂, is an organosilicon compound where two methyl (Me) groups are bonded to a central silicon atom. Additionally, the silicon holds two chlorine atoms, which are key to its chemical reactivity.

Silicon, unlike carbon, is adept at forming bonds with both oxygen and chlorine. This characteristic makes dimethyl dichlorosilane an interesting compound in the chemistry of silicon. The presence of these chlorine atoms creates a unique reactivity for hydrolysis—a reaction where the compound interacts with water.

The pivotal aspect of dimethyl dichlorosilane lies in its ability to undergo hydrolysis, wherein the chlorine atoms are replaced by hydroxyl (OH) groups. This reaction
- Sets the stage for the dimethyl dichlorosilane to perform further transformations in chemical reactions - Facilitates the production of hydroxyl-derived silicon products alongside water elimination, promoting the polymerization process.

Siloxane polymerization

Siloxane polymers are essential products in the chemical realm due to their unique properties and formation methods. Siloxane polymerization occurs when dimethyl dichlorosilane, after initial hydrolysis, forms intermediate compounds like (Me)₂Si(OH)₂. This compound

- Can further undergo condensation reactions, eliminating water molecules ( H₂O), and - Forms siloxane linkages noted as -O-(Me)₂Si-O-.

This process is pivotal in developing silicone-based polymers which
- Are known for their durability and versatility - Exhibit stability across a variety of chemical environments.

These siloxane linkages (linear chains or networks) provide mechanical properties such as elasticity and flexibility, making these polymers highly desirable in various industries, ranging from medical devices to consumer products. The fundamental ability of dimethyl dichlorosilane to polymerize through this process showcases its significance in material science.

Silicon compounds

Silicon compounds hold a special place in chemical industry and technology fields due to their diverse physical and chemical properties. Silicon, the second most abundant element in earth's crust, often forms compounds with oxygen, hydrogen, and carbon, besides other halides.

• Silicon-oxygen (Si-O) bonds are central to the formation of siloxanes, which are prominent silicon-based compounds in use.
• Organosilicon compounds, such as dimethyl dichlorosilane, represent a blend of organic methyl groups attached to the inorganic element silicon.

The unique feature of silicon compounds is their ability to form versatile structures, from simple molecules to expansive polymer networks.

These compounds are invaluable in various applications due to their:
- High thermal stability - Resistance to chemical corrosion - Flexibility and mechanical strength.
Advanced silicon compounds facilitate
- The development of electronic devices - Fabrication of high-performance materials - Innovations in medical and pharmaceutical products.