Problem 11 - A Complete Resource Book in Chemistry for JEE Main

Question

How many structural isomers of \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\) that are ethers? (a) 1 (b) 2 (c) 3 (d) 4

Step-by-Step Solution

Answer

Option (c) 3

Step 1: Understanding Ethers

Ethers are a class of organic compounds in which an oxygen atom is connected to two alkyl or aryl groups. Therefore, in the molecular formula \ \( \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O} \ \), we must identify structures where \( \rm{O} \) serves as the connecting unit between two carbon chains.

Step 2: Enumerating Possible Chains

First, consider dividing the carbon atoms into two different alkyl groups. We can partition four carbon atoms into two distinct groups, such as \( \mathrm{C}_{1}-\mathrm{C}_{3} \), \( \mathrm{C}_{2}-\mathrm{C}_{2} \), or \( \mathrm{C}_{3}-\mathrm{C}_{1} \). Each partition corresponds to two groups attached to the oxygen.

Step 3: Drawing Structural Isomers

1. \( \mathrm{C}_{3}-\mathrm{C}_{1} \) results in propyl methyl ether: \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2-\mathrm{O}-\mathrm{CH}_3 \).2. \( \mathrm{C}_{2}-\mathrm{C}_{2} \) results in two possibilities: - Diethyl ether: \( \mathrm{CH}_3\mathrm{CH}_2-\mathrm{O}-\mathrm{CH}_2\mathrm{CH}_3 \). - Ethyl methyl ether derived from rearranging substituents: \( \mathrm{CH}_3-\mathrm{O}-\mathrm{CH}\left( \mathrm{CH}_3 \right)\mathrm{CH}_2 \), which is impossible due to carbon constraints.3. For branched versions, isopropyl methyl ether can be considered: \( \mathrm{CH}_3\mathrm{CH}\left(\mathrm{CH}_3\right)-\mathrm{O}-\mathrm{CH}_3 \).

Step 4: Calculating Total Isomers

Verify the functionality of each structure to ensure it retains ether characteristics (an oxygen bonded to two carbon groups). Upon checking the isomers drawn: 1. Propyl Methyl Ether2. Diethyl Ether3. Isopropyl Methyl EtherIndeed, three structural ether isomers can exist for \( \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O} \).

Key Concepts

Ethers

Ethers are a fascinating class of organic compounds that contain an oxygen atom bonded to two carbon-containing groups. These groups can be alkyl or aryl, and they flank the oxygen in the molecular structure. In organic chemistry, ethers are characterized by their general formula: \( R-O-R' \), where \( R \) and \( R' \) are carbon groups. Ethers can vary widely, from simple compounds like diethyl ether to more complex structures. In the case of our example, \( ext{C}_4 ext{H}_{10} ext{O} \), the ether must incorporate the oxygen atom as a bridge between two separate carbon chains to maintain its ether nature. The task is to find different ways to arrange these carbon chains around the oxygen atom, resulting in structural isomers.

Organic Chemistry

Organic chemistry is the branch of chemistry that studies the structure, properties, and reactions of carbon-containing compounds. This field is vast, encompassing both simple molecules like methane as well as complex polymers and biochemicals. The key element in organic chemistry is carbon, known for its ability to form long chains and complex structures due to its four valence electrons. Organic molecules can be linear, branched, or cyclic, leading to a variety of potential isomers for a single molecular formula. Finding structural isomers, like with ethers, involves understanding how atoms rearrange while keeping the same molecular formula. This is a fundamental skill in organic chemistry, helping to reveal the diversity of organic compounds.

Carbon Chains

In the study of structural isomers, carbon chains play an essential role. These chains are series of connected carbon atoms that can vary in length and branching. For a molecule like \( ext{C}_4 ext{H}_{10} ext{O} \), understanding how to partition four carbon atoms into different chains is critical.

• The carbon atoms can form straight chains, such as in propyl groups.
• They can also branch, forming isopropyl groups and others.
• In the context of ethers, these variations determine different isomers.

All chains must connect back to the oxygen atom. Whether a carbon chain ends at the ether oxygen or continues in a new branch impacts the ether's structure. Observing these variations allows chemists to elucidate all possible structural isomers for a compound.

Molecular Structures

Molecular structures offer a visual representation of atoms and their bonds within a molecule. These structures are vital for identifying possible isomers, especially in compounds like ethers. In a molecule of \( ext{C}_4 ext{H}_{10} ext{O} \), visualizing the structure helps in rearranging atoms to find isomers.

• Structural illustrations clarify which carbon chains attach to the oxygen atom.
• They break down complex formulas into understandable parts.
• By drawing different configurations, chemists can explore all possible shapes ethers can adopt.

Thus, drawing aids in confirming how many distinct isomers exist for a given formula. This visual approach is a graphical method of problem-solving in organic chemistry, helping those who learn better through seeing rather than just reading or calculating. Utilizing molecular structures makes the abstract concepts of organic chemistry more concrete.