Question

Which of the following has the strongest C–X bond?

• A. CH\(_3\)–Cl
• B. CH\(_3\)–I
• C. CH\(_3\)–F
• D. CH\(_3\)–Br

Hint:

Bond strength increases as bond length decreases; hence C–F is strongest among C–X bonds.

Answer 1

The Correct Option is C

Step 1: Look at bond strength through bond dissociation energy instead of bond length.
Bond length and bond strength usually move in opposite directions, but it is worth checking through the energy needed to break each bond directly, since that is the literal definition of bond strength.

Step 2: Recall approximate C-X bond dissociation energies.
Typical values are roughly: $C-F \approx 485$ kJ/mol, $C-Cl \approx 327$ kJ/mol, $C-Br \approx 285$ kJ/mol, and $C-I \approx 213$ kJ/mol.

Step 3: Explain why C-F needs the most energy to break.
Fluorine is the smallest halogen and has the highest electronegativity, so its shared electron pair with carbon sits close and tightly held, giving the strongest orbital overlap of the group.

Step 4: Explain why C-I needs the least energy.
Iodine is the largest halogen here, and its bigger, more diffuse orbitals overlap poorly with the small carbon orbital, giving weak overlap and the lowest bond dissociation energy.

Step 5: Rank all four together.
\[ C{-}F \gt C{-}Cl \gt C{-}Br \gt C{-}I \]
This ranking by bond energy lines up with the ranking by bond length, confirming the same answer from a different angle.

Step 6: Final answer.
\[ \boxed{CH_3{-}F} \]