Question

Which of the following hydrogen bonds is likely to be the weakest?

• A. C–H$\cdots$O
• B. N–H$\cdots$O
• C. O–H$\cdots$O
• D. O–H$\cdots$F

Hint:

Hydrogen bond strength order: \[ \text{O–H} > \text{N–H} \gg \text{C–H} \] C–H hydrogen bonding is usually very weak or negligible.

Answer 1

The Correct Option is A

Concept: Strength of hydrogen bonding depends on:

• Electronegativity of atom bonded to H
• Polarity of X–H bond
• Lone pair availability on acceptor

More electronegative donor atom \(\Rightarrow\) stronger H-bond. Step 1: Compare donors Order of electronegativity: \[ \text{O} > \text{N} > \text{C} \] Thus: \[ \text{O–H} > \text{N–H} > \text{C–H} \] Conclusion: C–H bonds are weakly polar, hence weakest hydrogen bond.