Question

Which of the following is the molecular formula of cisplatin?

• A. \(\text{C}_{12}\text{H}_6\text{N}_2\text{Pt}\)
• B. \(\text{C}_6\text{H}_{12}\text{N}_2\text{O}_4\text{Pt}\)
• C. \(\text{C}_2\text{H}_8\text{N}_2\text{O}_3\text{Pt}\)
• D. \((\text{C}_{12}\text{H}_{14}\text{N}_2\text{O}_4)_2 \cdot (\text{Pt}^{2+})\)

Hint:

Always remember the exact formula of the big three platinum drugs: 1. Cisplatin = \(\text{PtCl}_2(\text{NH}_3)_2\) (No Carbons!) 2. Carboplatin = \(\text{C}_6\text{H}_{12}\text{N}_2\text{O}_4\text{Pt}\) 3. Oxaliplatin = \(\text{C}_8\text{H}_{14}\text{N}_2\text{O}_4\text{Pt}\)

Answer 1

The Correct Option is A

Concept: Cisplatin is one of the most famous and widely utilized platinum-based antineoplastic (anti-cancer) agents. It is primarily used to treat testicular, ovarian, bladder, and head and neck cancers. It acts by cross-linking DNA, which ultimately triggers apoptosis in rapidly dividing cancer cells.

Step 1: Analyzing the true chemical structure of Cisplatin.
The universally accepted chemical name for cisplatin is cis-diamminedichloroplatinum(II). Breaking this down structurally:
• The central atom is a Platinum (Pt) ion in the +2 oxidation state.
• It has two ammine (\(\text{NH}_3\)) ligands.
• It has two chloride (\(\text{Cl}^-\)) ligands.
• The "cis" geometry means that the two similar ligands are adjacent (at a \(90^\circ\) angle) to each other in a square planar coordination complex. Therefore, the true molecular formula for actual cisplatin is \(\text{PtCl}_2(\text{NH}_3)_2\) or \(\text{H}_6\text{Cl}_2\text{N}_2\text{Pt}\). Notice that true cisplatin contains absolutely no carbon atoms.

Step 2: Evaluating the provided options and the exam's context.
Let us look at the options provided in the question:
• Option (A) \(\text{C}_{12}\text{H}_6\text{N}_2\text{Pt}\): The image's answer key indicates this is the correct answer. However, chemically speaking, a complex with 12 carbons is definitively not cisplatin. This formula likely refers to an organometallic derivative, a specialized intercalating platinum complex (such as a phenanthroline-platinum complex where phenanthroline is \(\text{C}_{12}\text{H}_8\text{N}_2\), making the formula match closely), or it represents a severe typographical error in the original examination paper where the examiner conflated cisplatin with another metallodrug.
• Option (B) \(\text{C}_6\text{H}_{12}\text{N}_2\text{O}_4\text{Pt}\): This is the molecular formula for Carboplatin, another widely used platinum-based anti-cancer drug that was developed to have less nephrotoxicity than cisplatin. It contains a cyclobutane dicarboxylate ligand (providing the carbons and oxygens).
• Option (C) \(\text{C}_2\text{H}_8\text{N}_2\text{O}_3\text{Pt}\): This formula corresponds to a different oxo-platinum complex but does not match standard chemotherapy agents.
• Option (D) \((\text{C}_{12}\text{H}_{14}\text{N}_2\text{O}_4)_2 \cdot (\text{Pt}^{2+})\): This represents a massive, complex organoplatinum salt, not a small square planar molecule. Conclusion: While the true chemical formula of cisplatin (\(\text{PtCl}_2(\text{NH}_3)_2\)) is glaringly absent from the options, in the strict context of the provided examination paper's key, Option 1 is marked as the correct answer. When facing such defective questions in competitive exams, students are often forced to choose the "official" key or the question is later challenged and dropped.