Preparation of Butane from Ethene: A Comprehensive Guide

Butane, an important hydrocarbon widely used in various industries, can be synthesized from ethene, a simpler alkene. This guide will outline several methods to prepare butane from ethene, detailing each step and the relevant chemical reactions involved.

Method 1: Catalytic Hydrogenation and Halogenation

A straightforward approach is to use catalytic hydrogenation to start from ethene. Let's walk through the steps:

Step 1: Catalytic Hydrogenation

1. Ethene can be hydrogenated to form ethane:

C2H4 H2 → C2H6

Step 2: Halogenation

2. Ethane can then be halogenated using chlorine or bromine, yielding ethyl chloride (C2H5Cl) or ethyl bromide (C2H5Br):

C2H6 Cl2 (or Br2) → C2H5Cl (or C2H5Br)

Step 3: Wurtz Reaction (Coupling Reaction)

3. Sodium (Na) in dry ether can be used to form a radical from ethyl chloride or ethyl bromide:

C2H5Cl Na → C2H5· NaCl

The radical (C2H5·) can couple with another ethyl radical to form butane (C4H10):

C2H5· C2H5· → C4H10

Method 2: Direct Hydrobromination and Reaction with Sodium Acetylide

Another method involves:

Step 1: Direct Hydrobromination of Ethene

Hydrobromination of ethene directly yields bromoethane (C2H5Br):

C2H4 HBr → C2H5Br

Step 2: Reaction with Sodium Acetylide

Subsequently, bromoethane reacts with sodium acetylide (CH3CH2CN) in the presence of sodium (Na) in dry ether to form but-1-yne (C4H5):

C2H5Br CH3CH2CN Na → C4H5 NaCl

The ungenesis of but-1-yne can then undergo further reaction to butane (C4H10) under certain conditions, although this might require additional steps or catalysts.

Method 3: Hydration and Chlorination

Another approach involves:

Step 1: Hydration of Ethene

Hydration of ethene to form ethanol (C2H5OH):

C2H4 H2SO4 → C2H5OH H2SO4

Step 2: Chlorination of Ethanol

Chlorination of ethanol using thionyl chloride (SOCl2):

C2H5OH SOCl2 → C2H5Cl SO2 HCl

Step 3: Reaction with Sodium Acetylide

Reaction of chloroethane (C2H5Cl) with sodium acetylide (CH3CH2CN) yields butyne (C4H5) or butane (C4H10):

C2H5Cl CH3CH2CN Na → C4H5 NaCl (or C4H10 under further reduction)

Considerations

While these synthetic routes demonstrate the theoretical conversion of ethene to butane, it's important to consider the practicality and expense. Naturally occurring ethene and butane are readily available and widely used in the chemical industry, making them preferred choices over artificial synthesis methods.

Conclusion

Although synthesizing butane from ethene is theoretically possible, it is often more feasible to use the naturally occurring substances. However, these methods can provide valuable insights into organic chemistry and are useful in academic and laboratory settings.