Wurtz Fittig Reaction — the NEET Chemistry reaction: mechanism, reagents, conditions, structures and exam traps.
Wurtz-Fittig Reaction The Wurtz-Fittig reaction is a coupling reaction in organic chemistry that involves the reaction of an aryl halide with an alkyl halide in the presence of sodium metal in an anhydrous ethereal solution to form a substituted aromatic compound (an alkylarene). It is an extension of the Wurtz reaction for synthesizing aromatic derivatives. Sodium metal is a silvery, soft metal that tarnishes rapidly upon exposure to air. During the reaction, the sodium metal will visibly react, dissolving over time. The reaction is often exothermic. A white precipitate of sodium halide (e.g., NaCl, NaBr, NaI) will typically form in the ethereal solution. Generally thermodynamically favorable due to the formation of a stable carbon-carbon bond and the more stable ionic sodium halide byproduct. 1. Electron transfer from sodium metal to the aryl halide, forming an aryl radical and a sodium halide. 2. Electron transfer from sodium metal to the alkyl halide, forming an alkyl radical and a sodium halide. 3. The aryl radical and alkyl radical combine to form a new carbon-carbon bond, yielding the alkylarene product. 4. Alternatively, organosodium intermediates (Ar-Na and R-Na) can be formed, which then react to produce the coupled product and sodium halide. Side reactions: The Wurtz reaction (R-R coupling from two alkyl halides) and Fittig reaction (Ar-Ar coupling from two aryl halides) can occur, leading to a mixture of products. Improper solvent: The reaction requires anhydrous (dry) ether because sodium metal reacts vigorously with water or alcohols. Poor choice of alkyl halide: Tertiary alkyl halides often undergo elimination (E2) reactions instead of coupling. Aryl chlorides are less reactive than bromides or iodides and may not react or require harsher conditions. Not suitable for molecules with reducible functional groups.