See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: The starting material Ph–CH=NO2H is a nitroso compound in its tautomeric (aci) form, which can be written as phenylmethylene nitronic acid or more precisely as the aci-form of phenylnitromethane. This is the nitronic acid tautomer (aci-nitro form) of Ph–CH2–NO2 (phenylnitromethane). The aci-nitro form Ph–CH=NO2H and the nitro form Ph–CH2–NO2 are tautomers of each other. Step 1: Identify the starting material. Ph–CH=NO2H is the aci-nitro (nitronic acid) tautomer of phenylnitromethane. It has the structure where carbon is double-bonded to nitrogen, with an OH on nitrogen. Step 2: Tautomerism between the aci-nitro form and the nitro form. The aci-nitro form (Ph–CH=NO2H) isomerises to the more stable nitro form (Ph–CH2–NO2). This is a well-known tautomeric equilibrium: the nitro–aci-nitro tautomerism. Under the given conditions (slow, 3 days, 50–50% mixture), the system reaches equilibrium between the aci form and the true nitro form. Step 3: The isomer (x) formed is Ph–CH2–NO2 (phenylnitromethane), which is the nitro tautomer. This corresponds to option (b). Step 4: Why other options fail: - Option (a) Ph–NO–CH2OH: This would require breaking of the C–N bond and formation of a new O–C bond — a structural isomer, not a tautomer, and not formed under these mild conditions. - Option (c) Ph–NH–CO2H: This is a carbamate-type structure requiring complete rearrangement; not consistent with simple tautomerism. - Option (d) None: Incorrect because option (b) is valid. Therefore, the correct answer is B.