Question

Wurtz reaction converts alkyl halide into alkane when it is made to react with (1) Na in alcohol (2) Na in dry ether (3) \(\mathrm{Zn}\) in alcohol (4) \(\mathrm{Zn}\) in dry ether

Short answer

The Wurtz reaction occurs with Na in dry ether.

Step-by-step solution

Understand the Reaction

The Wurtz reaction is used to couple two alkyl halides to form a higher alkane. It involves the use of a specific metal in a non-aqueous condition as the reagent.

Identify the Metal

In the Wurtz reaction, sodium (Na) is the metal typically used. It facilitates the coupling by providing electrons to form free radicals from the alkyl halides.

Determine the Solvent

The solvent for the Wurtz reaction must be an anhydrous (dry) organic solvent to prevent reaction with water. Dry ether is commonly used.

Match the Options

Among the given options, check which one involves sodium (Na) in a dry organic solvent (dry ether). The correct choice is (2) Na in dry ether.

Key concepts

Alkyl Halide

An alkyl halide, also known as a haloalkane, is a compound in which a halogen atom (such as chlorine, bromine, or iodine) is bonded to an alkyl group. The general formula for an alkyl halide is \(R-X\), where \(R\) represents the alkyl group and \(X\) represents the halogen.
Alkyl halides are classified based on the nature of the carbon atom to which the halogen is attached:

• Primary (1°) alkyl halide: The halogen is attached to a carbon atom that is bonded to only one other carbon atom.
• Secondary (2°) alkyl halide: The halogen is attached to a carbon atom that is bonded to two other carbon atoms.
• Tertiary (3°) alkyl halide: The halogen is attached to a carbon atom that is bonded to three other carbon atoms.

Alkyl halides are crucial in organic chemistry because they serve as starting materials for the synthesis of various organic compounds, including alkanes through reactions like the Wurtz reaction.

Alkane

Alkanes are saturated hydrocarbons consisting only of carbon (C) and hydrogen (H) atoms, connected by single bonds. Their general formula is \(C_nH_{2n+2}\).
Some important characteristics of alkanes include:

• They are nonpolar molecules due to the similar electronegativities of carbon and hydrogen.
• They have relatively low reactivity because their C-C and C-H bonds are stable.
• They are found in large quantities in natural gas and crude oil.

Alkanes are used as fuel and solvents and serve as starting materials in the production of various chemicals. In a Wurtz reaction, alkanes are formed as the product through the coupling of alkyl halides.

Sodium Na

Sodium (Na) is an alkali metal, highly reactive and commonly found in nature as its compounds, such as sodium chloride (table salt). In organic chemistry, sodium is often used as a reducing agent.
In the Wurtz reaction, sodium plays a crucial role by:

• Providing electrons to form free radicals from the alkyl halides.
• Helping to couple these free radicals to form a higher alkane.

Due to its high reactivity, sodium must be handled with care, especially in reactions that require anhydrous conditions, to prevent unwanted side reactions with water or moisture.

Dry Ether

Dry ether, also known as anhydrous ether, is a solvent that is free of water. Its common chemical formula is \(C_2H_5OC_2H_5\) (diethyl ether).
In the Wurtz reaction, dry ether is essential because:

• It creates a non-aqueous environment, preventing the highly reactive sodium from reacting with water or moisture.
• It dissolves the alkyl halides effectively, allowing them to interact with sodium more efficiently.

The use of dry ether ensures a controlled reaction environment, which is crucial for the successful coupling of alkyl halides to form alkanes.