Q.How would you prepare ethane from methyl iodide?

Wurtz reaction uses sodium metal in dry ether to couple alkyl halides into a higher alkane.

In the Wurtz reaction, two molecules of an alkyl halide react with sodium metal in dry ether to give a symmetrical alkane with twice the number of carbon atoms:

2 R-X + 2 Na --(dry ether)--> R-R + 2 NaX

…

Aryl halide + alkyl halide + Na in dry ether = Wurtz-Fittig reaction, giving an alkyl arene.

When an aryl halide (C6H5X) and an alkyl halide (RX) are treated together with sodium in dry ether, the two are coupled to give an alkylbenzene:

C6H5-X + 2 Na + R-X --(dry ether)--> C6H5-R + 2 NaX

…

Wurtz–Fittig type coupling of two aryl halide molecules with sodium in dry ether gives biphenyl (diphenyl).

Chlorobenzene reacts with sodium metal in the presence of dry ether (the Fittig reaction, the aryl-aryl analogue of the Wurtz reaction):

$2\,C_6H_5Cl + 2Na \xrightarrow{\text{dry ether}} C_6H_5-C_6H_5 + 2NaCl$

…

The Fittig reaction couples two molecules of an aryl halide using sodium metal in dry ether, giving a diaryl compound - the aromatic analogue of the Wurtz reaction.

When an aryl halide (e.g. bromobenzene) is treated with sodium metal in dry ether, two aryl groups couple together to form a symmetrical biaryl compound, releasing sodium halide:

2 C6H5Br + 2 Na --(dry ether)--> C6H5-C6H5 (Biphenyl) + 2 NaBr

…

Alkyl halide + sodium in dry ether couples two alkyl groups to give an alkane — the Wurtz reaction.

In the Wurtz reaction, two molecules of an alkyl halide react with sodium metal in dry ether to give a symmetrical alkane containing twice the number of carbon atoms:

2 R–X + 2Na ---> R–R + 2NaX

For example, 2CH3CH2Br + 2Na ---> CH3CH2CH2CH3 + 2NaBr.

…

2 C6H5X + 2Na (ether) → C6H5-C6H5 (biphenyl) is the Fittig reaction — the aromatic version of the Wurtz coupling.

The reaction 2(C6H5-X) + 2Na --dry ether--> C6H5-C6H5 + 2NaX couples two aryl halide molecules using sodium metal to form a biaryl (biphenyl).

• Wurtz reaction: two alkyl halides + Na → higher alkane (alkyl-alkyl coupling).
• Fittig reaction: two aryl halides + Na → biaryl (aryl-aryl coupling) — exactly the reaction shown. …

The Wurtz reaction couples two alkyl halide molecules using sodium metal in dry ether to give a higher (symmetrical) alkane.

When an alkyl halide is treated with sodium metal in dry ether, the two alkyl groups couple together to form a higher alkane containing double the number of carbon atoms, with the elimination of sodium halide.

General equation:

2R–X + 2Na --(dry ether)--> R–R + 2NaX

Example: 2CH3Br + 2Na --(dry ether)--> CH3–CH3 (ethane) + 2NaBr

…

The Fittig reaction couples two molecules of an aryl halide using sodium metal in dry ether to give a symmetrical biaryl (an extension of the Wurtz reaction to aromatic halides).

The Fittig reaction is the aromatic analogue of the Wurtz reaction: when an aryl halide is treated with sodium metal in dry ether, two aryl groups couple together to form a symmetrical biaryl compound, with sodium halide as the by-product.

Mechanism outline: sodium generates aryl free radicals/aryl-sodium intermediates from the aryl halide, and two such aryl species couple to form the new C–C bond joining the two rings.

Equation (bromobenzene → biphenyl):

$2C_6H_5Br + 2Na \xrightarrow{\text{dry ether}} C_6H_5{-}C_6H_5 + 2NaBr$

Here two molecules of bromobenzene react with sodium in dry ether to give biphenyl and sodium bromide.

…

The Wurtz reaction (haloalkane + Na, dry ether) is the standard method for converting a haloalkane into a higher (doubled-carbon) alkane — option (b).

$2R{-}X + 2Na \xrightarrow{\text{dry ether}} R{-}R + 2NaX$

Kolbe's reaction is the electrolysis of a sodium/potassium salt of a carboxylic acid to give an alkane (not from a haloalkane); coupling reaction usually refers to azo-coupling of diazonium salts; hydrolysis of a haloalkane gives an alcohol …

Wurtz reaction couples two molecules of an alkyl halide over sodium metal in dry ether, giving a symmetrical alkane with double the carbon count.

$2R{-}X + 2Na \xrightarrow{\text{dry ether}} R{-}R + 2NaX$

For example, 2CH$_3$CH$_2$Br + 2Na → CH$_3$CH$_2$–CH$_2$CH$_3$ (n-butane) + 2NaBr. It is a useful method for preparing symmetrical higher alkanes containing an even number of carbon atoms, but gives a mixture of three products (not useful) if two different alkyl halide …

The Wurtz-Fittig reaction couples an aryl halide with a primary alkyl halide using sodium, cleanly giving a straight-chain alkylbenzene without carbocation rearrangement.

$n$-Propylbenzene ($C_6H_5-CH_2CH_2CH_3$) needs a straight $n$-propyl chain attached to benzene. Friedel–Crafts alkylation of benzene with 1-chloropropane is unsuitable because the intermediate primary carbocation readily rearranges (via a hydride shift) to the more stable secondary carbocation, giving mainly isopropylbenzene (cumene) instead. The Wurtz-Fittig reaction — treating chlorobenzene with 1-chloropropane and sodium metal in dry ether — proceeds via a different …