Problem 88 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Which of the following is an isomer of diethyl ether (a) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}\) (b) \(\mathrm{CH}_{3} \mathrm{CHO}\) (c) \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}\) (d) \(\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{CHOH}\)

Step-by-Step Solution

Answer

Option (a) \((\text{CH}_3)_3\text{COH}\) is an isomer of diethyl ether.

Step 1: Understanding Isomers

Isomers are molecules with the same molecular formula but different structures. We must find an option with the same molecular formula as diethyl ether.

Step 2: Identify the Molecular Formula of Diethyl Ether

Diethyl ether, with structure \(( ext{C}_2 ext{H}_5)_2 ext{O}\), has the molecular formula \( ext{C}_4 ext{H}_{10} ext{O}\), which consists of four carbon atoms, ten hydrogen atoms, and one oxygen atom.

Step 3: Determine the Molecular Formulas of Options

- Option (a): \(( ext{CH}_3)_3 ext{COH}\) corresponds to \( ext{C}_4 ext{H}_{10} ext{O}\).- Option (b): \( ext{CH}_3 ext{CHO}\) corresponds to \( ext{C}_2 ext{H}_4 ext{O}\).- Option (c): \( ext{C}_3 ext{H}_7 ext{OH}\) corresponds to \( ext{C}_3 ext{H}_8 ext{O}\).- Option (d): \(( ext{C}_2 ext{H}_5)_2 ext{CHOH}\) corresponds to \( ext{C}_5 ext{H}_{12} ext{O}\).

Step 4: Compare Molecular Formulas

Among the options, only option (a), \(( ext{CH}_3)_3 ext{COH}\), has the same molecular formula \( ext{C}_4 ext{H}_{10} ext{O}\) as diethyl ether, indicating it is an isomer.

Key Concepts

Molecular Formula

Understanding the concept of a molecular formula is essential in organic chemistry. A molecular formula represents the exact number and type of atoms in a molecule. For example, diethyl ether, a common compound, has the molecular formula \( \text{C}_4\text{H}_{10}\text{O} \). This formula tells us that each molecule contains four carbon (C) atoms, ten hydrogen (H) atoms, and one oxygen (O) atom.

Molecular formulas are like the blueprint of a molecule. They provide the basic information needed to understand the components of a chemical compound, but not necessarily how these components are arranged structurally. In some cases, different molecules can share the same molecular formula but have different structures, leading to the fascinating topic of isomers, which we will explore further.

Structural Formula

While a molecular formula gives you the count of each type of atom in a molecule, a structural formula provides insight into how these atoms are connected. It serves as a detailed map of the molecular structure, showcasing bonds and arrangements, and helping us see the difference between seemingly similar compounds.

For example, diethyl ether can be structured as \((\text{C}_2\text{H}_5)_2\text{O}\), where the ethyl groups (\(\text{C}_2\text{H}_5\)) are bonded to an oxygen atom. In contrast, the structural formula for an isomer like tert-butanol is \((\text{CH}_3)_3\text{COH}\). This shows that the same atoms are connected differently, leading to distinct physical and chemical properties.

• Structural formulas allow chemists to visualize how changes in structure can lead to different isomeric forms.
• This visualization helps in predicting the properties and reactivity of the molecules.

Isomer Identification

Identifying isomers involves recognizing molecules that have the same molecular formula but differ in their structural arrangements. Diethyl ether and tert-butanol, for instance, share the molecular formula \(\text{C}_4\text{H}_{10}\text{O}\), but their structures are different.

To identify isomers effectively, follow these steps:

• First, determine the molecular formula of the compound in question.
• Next, explore all possible structural arrangements of the atoms in the molecule.
• Compare these structures to find if they are distinct, yet preserving the same molecular formula.

Recognizing isomers is crucial in organic chemistry because isomers often possess very different properties despite having the same molecular formula, which can impact their uses in chemical reactions and industrial applications. Being able to discern these differences is a fundamental skill in understanding complex organic interactions.