Problem 192 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I 1\. Formalin 2\. Trioxane 3\. Ketene 4\. Metaldehyde List II (i) Trimer of \(\mathrm{HCHO}\) (ii) Compounds of the general formula, \(\mathrm{R}_{2} \mathrm{C}=\mathrm{C}=\mathrm{O}\) (iii) A tetramer of acetaldehyde (iv) \(40 \%\) aqueous solution of \(\mathrm{HCHO}\)

Step-by-Step Solution

Answer

1-(iv), 2-(i), 3-(ii), 4-(iii).

Step 1: Understand the Items in List I

The goal is to identify what each term in List I represents. Formalin is a known solution of formaldehyde. Trioxane is a polymer, specifically a trimer. Ketene refers to compounds with the general formula \(\mathrm{R}_{2}\mathrm{C}=\mathrm{C}=\mathrm{O}\), and Metaldehyde is a polymer form of acetaldehyde.

Step 2: Match Item 1 (Formalin) from List I

Formalin is a \(40\%\) aqueous solution of \(\mathrm{HCHO}\), thus it matches with (iv).

Step 3: Match Item 2 (Trioxane) from List I

Trioxane is a trimer of formaldehyde (\(\mathrm{HCHO}\)), which corresponds to (i) in List II.

Step 4: Match Item 3 (Ketene) from List I

Ketene refers to compounds of the general formula \(\mathrm{R}_{2}\mathrm{C}=\mathrm{C}=\mathrm{O}\), which matches with (ii) in List II.

Step 5: Match Item 4 (Metaldehyde) from List I

Metaldehyde is a tetramer of acetaldehyde, which corresponds to (iii) in List II.

Key Concepts

Formalin

Formalin is a chemistry term that you might encounter in your studies. It refers to a solution containing formaldehyde. Specifically, it's a 40% aqueous solution of formaldehyde (\(\mathrm{HCHO}\)). This solution is commonly used for preserving biological specimens in labs, making it a valuable tool for students and professionals in biology and chemistry.
When you think of Formalin, it's important to remember what it consists of:

• Formaldehyde: A simple aldehyde with the formula \(\mathrm{HCHO}\), often used in its pure form as a disinfectant or preservative.
• Aqueous Solution: The presence of water in the mix that makes it easier to use for various biological and chemical processes.

Learning about Formalin helps you understand how compounds are used practically in laboratories. It's a common solution across multiple scientific disciplines, showing the overlap between chemistry and other fields.

Trioxane

Trioxane is a fascinating compound in chemistry that represents more complex structures formed from simpler molecules. It is a polymer and, more specifically, a trimer of formaldehyde (\(\mathrm{HCHO}\)). This means it consists of three formaldehyde molecules linked together. Such structures are significant because they illustrate the transformation of a simple molecule (like formaldehyde) into a more complex and stable compound through polymerization.
Understanding Trioxane involves noting:

• Trimer: A type of oligomer formed by the polymerization of three monomer units (in this case, formaldehyde molecules).
• Polymerization: The chemical process that combines multiple small molecules to form larger, more complex structures.

This compound not only shows the wonder of molecular chemistry but also is relevant in industrial applications and research involving formaldehyde.

Ketenes

Ketenes are a group of organic compounds that have a characteristic chemical structure. Their general formula is \(\mathrm{R}_{2}\mathrm{C} = \mathrm{C} = \mathrm{O}\), where \(\mathrm{R}\) represents an organic substituent. This distinct structure makes Ketenes highly reactive, allowing them to be used in various chemical reactions to synthesize different products.
There are key features of Ketenes that are important:

• Reactivity: The carbon-carbon double bond and carbon-oxygen double bond make them ideal for participating in addition reactions.
• Versatility: Used in several chemical pathways to form new products, making them valuable in organic chemistry synthesis.

Ketenes are often discussed in advanced organic chemistry due to their unique properties and wide range of applications in chemical synthesis.

Metaldehyde

Metaldehyde is another intriguing example of chemical compounds formed through polymerization. It is known as a tetramer of acetaldehyde (\(\mathrm{CH}_{3}\mathrm{CHO}\)), meaning it contains four acetaldehyde units linked together. In practical terms, it's mostly used as a pesticide, particularly against slugs and snails, because of its chemical properties.
Some important aspects to remember about Metaldehyde are:

• Tetramer: It's formed by four repeating units of acetaldehyde, similar to how Trioxane is formed from formaldehyde.
• Usage: Its role as a pesticide in agriculture highlights its application in everyday life.

These features make Metaldehyde a perfect study topic for understanding both polymerization and practical applications of chemical compounds.