Question

In which of the following liquid inter molecular hydrogen bonding does not exist?

• A. $CH_3COOH$
• B. $C_2H_5OH$
• C. Phenol
• D. Diethylether
• E. Ethylamine

Hint:

Ethers have lower boiling points than alcohols because they lack H-bonding.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question asks to identify the compound that cannot form intermolecular hydrogen bonds. Hydrogen bonding is a strong type of dipole-dipole interaction that occurs in molecules.
Step 2: Key Formula or Approach:
For a substance to exhibit intermolecular hydrogen bonding, its molecules must contain: 1. A hydrogen atom that is covalently bonded to a highly electronegative atom (primarily Fluorine, Oxygen, or Nitrogen). This creates a highly polarized bond and a very electron-deficient hydrogen. 2. A lone pair of electrons on a nearby F, O, or N atom (in another molecule) that can attract this electron-deficient hydrogen. In simple terms, look for an H atom directly attached to an F, O, or N. Step 3: Detailed Explanation:
Let's examine the structure of each molecule: - (A) CH\(_3\)COOH (Acetic acid): Contains an -O-H group. The hydrogen is bonded to a highly electronegative oxygen atom. Acetic acid can form strong hydrogen bonds (it typically exists as a dimer in the liquid and vapor phases). - (B) C\(_2\)H\(_5\)OH (Ethanol): Contains an -O-H group. The hydrogen is bonded to a highly electronegative oxygen atom. Ethanol can form strong hydrogen bonds. - (C) Phenol (C\(_6\)H\(_5\)OH): Contains an -O-H group attached to a benzene ring. The hydrogen is bonded to a highly electronegative oxygen atom. Phenol can form strong hydrogen bonds. - (D) Diethylether (C\(_2\)H\(_5\)-O-C\(_2\)H\(_5\)): Contains an oxygen atom, which has lone pairs. However, all the hydrogen atoms are bonded to carbon atoms. The C-H bond is not polarized enough for the hydrogen to participate in hydrogen bonding. Since there is no H atom directly bonded to O, F, or N, diethylether cannot form hydrogen bonds with itself (intermolecularly). It can act as a hydrogen bond acceptor with other molecules like water, but not among its own molecules. - (E) Ethylamine (C\(_2\)H\(_5\)NH\(_2\)): Contains an -N-H group. The hydrogen is bonded to a highly electronegative nitrogen atom. Ethylamine can form hydrogen bonds. Step 4: Final Answer:
Diethylether is the liquid in which intermolecular hydrogen bonding does not exist.