Cyanate ion structure from Wöhler synthesis rearrangement

Steps:

• Ammonium cyanate formula is NH₄OCN, indicating NH₄⁺ paired with a cyanate anion.
• Heating yields urea, (NH₂)₂CO, via isomerization with no other products.
• The reaction NH₄OCN → (NH₂)₂CO rearranges the O-C-N framework into the carbamide structure.
• This confirms the anion as linear OCN⁻, matching the empirical formula and product.

Why C is correct:

• OCN⁻ is the standard cyanate ion formula, with resonance structures ⁻O-C≡N ↔ O≡C-N⁻, enabling the exact atomic rearrangement to urea.

Why the others are wrong:

• A. CN⁻ is the cyanide ion, which would produce hydrogen cyanide or nitriles, not urea.
• B. CNO⁻ implies a non-linear or unstable arrangement, incompatible with the observed urea formation.
• D. NCO⁻ denotes the isocyanate ion (⁻N=C=O), leading to different polymerization products, not isolated urea.

Final answer: C