Determine the locant number assigned to the spiro carbon atom in the correct IUPAC sequential number — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Numbering starts at a carbon adjacent to the spiro carbon in the smaller ring (which contains 3 non-spiro carbons) and proceeds around the smaller ring. The sequence is C1, C2, C3 for the smaller ring, making the shared spiro carbon atom position number 4.