Question

Which among the following compounds has highest melting point?

• A. tert-Butyl alcohol
• B. n-Butyl alcohol
• C. Isobutyl alcohol
• D. sec-Butyl alcohol

Hint:

Symmetry rules melting points! Symmetrical and spherical shapes like tert-butyl groups pack perfectly into crystal grids, sending their melting points sky-high compared to asymmetric chains.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks us to identify the specific structural isomer of butyl alcohol ($\text{C}_4\text{H}_{10}\text{O}$) that possesses the highest melting point.

Step 2: Detailed Explanation:
The melting point of organic structural isomers depends heavily on molecular symmetry and structural packing efficiency in the crystal lattice.

• tert-Butyl alcohol ($\text{(CH}_3)_3\text{COH}$) features a highly symmetrical, compact, and spherical pseudo-globular structure.

• Because of this exceptional spherical symmetry, the molecules pack much more tightly and neatly into a rigid crystal lattice compared to its linear or less symmetrical branched isomers (n-butyl, isobutyl, and sec-butyl alcohols).

• A more compact and well-packed crystal lattice requires significantly more thermal energy to break apart, leading to an exceptionally high melting point (around $25^\circ\text{C}$ to $26^\circ\text{C}$, making it a solid or near-solid at room temperature), whereas the other open isomers melt well below $ -50^\circ\text{C}$.


Step 3: Final Answer:
The compound with the highest melting point is tert-Butyl alcohol, which corresponds to option (A).