Problem 42 - A Complete Resource Book in Chemistry for JEE Main

Question

An isomer of ethanol is (a) methanol (b) diethyl ether (c) acetone (d) dimethyl ether

Step-by-Step Solution

Answer

The isomer of ethanol is (d) dimethyl ether.

Step 1: Understand Isomers

Isomers are compounds with the same molecular formula but different structures. This means they have the same number and types of atoms, but the arrangement of these atoms is different.

Step 2: Identify Ethanol's Molecular Formula

Ethanol has the molecular formula \( C_2H_6O \). It consists of 2 carbon (C), 6 hydrogen (H), and 1 oxygen (O) atom.

Step 3: Examine the Options

Let's examine the molecular formulas of the options given: (a) Methanol: \( CH_4O \) (b) Diethyl ether: \( C_4H_{10}O \) (c) Acetone: \( C_3H_6O \) (d) Dimethyl ether: \( C_2H_6O \)

Step 4: Compare to Ethanol

We need to find a compound from the options that has the same molecular formula as ethanol, \( C_2H_6O \): - Methanol \( CH_4O \) does not match. - Diethyl ether \( C_4H_{10}O \) does not match. - Acetone \( C_3H_6O \) does not match. - Dimethyl ether \( C_2H_6O \) matches and thus, is an isomer of ethanol.

Key Concepts

Ethanol

Ethanol is a simple alcohol known for its presence in alcoholic beverages. Its molecular formula is simple yet precise: \( C_2H_6O \). Ethanol consists of two carbon atoms, six hydrogen atoms, and one oxygen atom. Provides warmth to the body when consumed not only due to its calorific nature but also due to its simple molecular arrangement which allows it to be metabolized easily by the body.
Ethanol molecules consist of a functional group, the hydroxyl group (\(-OH\)), which plays a crucial role in its properties and reactions. This group attaches to a carbon chain, making the compound both soluble in water and volatile, further contributing to its effectiveness as a solvent and its use in the industry. It is commonly found in products like cleaning agents, fuels, and pharmaceuticals as well. Understanding ethanol at a molecular level helps in appreciating its versatility and extensive use.

Molecular Formula

A molecular formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. It specifies the actual number of atoms of each element in a molecule. For instance, the molecular formula of ethanol, \( C_2H_6O \), gives a straightforward depiction of its chemical composition.
It shows that each molecule of ethanol comprises two carbon atoms, six hydrogen atoms, and one oxygen atom, without detailing the specific structure or the arrangement of atoms.

• A molecular formula is essential for identifying isomers—compounds that share the same formula yet differ structurally.
• While it tells us the basic composition, it doesn't provide information on the structure or connectivity of atoms.
• For more complex molecules, molecular formulas serve as a foundational step in determining structural variations and stereochemistry.

Recognizing the molecular formula is crucial in chemistry to not only identify compounds but to also differentiate the myriad ways they can be interlinked into isomers.

Dimethyl Ether

Dimethyl ether is an interesting compound due to its role as an isomer of ethanol. Both ethanol and dimethyl ether share the same molecular formula, \( C_2H_6O \), yet they exhibit significantly different properties due to distinct structural configurations.
In ethanol, the oxygen atom is bonded to a carbon and hydrogen (alcohol), whereas in dimethyl ether, the oxygen links two methyl groups (\(-CH_3\)). This variation in structure leads to divergent boiling points, solubility, and reactivity between the two.

• Dimethyl ether serves prominently in chemical industries as a potential alternative fuel and a propellant in aerosols.
• It is non-toxic and, due to its lower boiling point compared to ethanol, it evaporates rapidly, making it an efficient fuel and solvent.
• Understanding dimethyl ether enhances comprehension of how slight structural changes lead to different physical and chemical properties.

Exploring dimethyl ether as an isomer of ethanol illustrates the broader concept of structural isomerism, showcasing nature’s ability to manifest diverse functionalities from similar atomic arrangements.