Wurtz-Fittig Reaction — Mechanism and Examples

General Equation:

Ar-X + R-X + 2Na → Ar-R + 2NaX

(in dry ether)

Where:

• Ar-X = aryl halide (e.g., bromobenzene, C₆H₅Br)
• R-X = alkyl halide (e.g., methyl bromide, CH₃Br)
• Na = sodium metal
• Ar-R = alkylarene (e.g., toluene, C₆H₅CH₃)

Specific Example: C₆H₅Br + CH₃Br + 2Na → C₆H₅CH₃ (Toluene) + 2NaBr

The mechanism proceeds via carbanion intermediates (organosodium compounds):

Step 1: Sodium reacts with the alkyl halide: R-X + 2Na → R-Na (organosodium) + NaX

Step 2: The organosodium compound reacts with the aryl halide: R-Na + Ar-X → Ar-R + NaX

The alkyl group from the alkyl halide gets attached to the arene ring.

The Wurtz reaction uses only alkyl halides. The Wurtz-Fittig specifically involves an aryl halide.

1. Mixed products: Along with the desired Ar-R, the reaction also produces Ar-Ar (from two aryl halides) and R-R (from two alkyl halides) as by-products.
2. Aryl halides alone won't work: Pure aryl halides do not undergo the original Wurtz reaction because the Ar-Na bond forms but is too stable to react further with another aryl halide.
3. Works best with primary alkyl halides — secondary and tertiary halides cause elimination side reactions.