Problem 22 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

What would be the product formed when 1-bromo-3-chlorocyclobutane reacts with two equivalents of metallic sodium in ether?

Step-by-Step Solution

Answer

The product is bicyclo[1.1.0]butane.

Step 1: Understand The Reaction Type

The reaction involves 1-bromo-3-chlorocyclobutane and metallic sodium in ether. This is a typical setup for a Wurtz reaction, where two halides react with sodium to form an alkane.

Step 2: Identify the Halides

1-bromo-3-chlorocyclobutane contains two halides: a bromine at the 1-position and a chlorine at the 3-position. Both of these groups can participate in the Wurtz reaction.

Step 3: Determine The Bond Formation

In a Wurtz reaction, the sodium metal provides electrons to create radicals from the halide positions. These radicals then couple to form new carbon-carbon bonds. Here, the bromide and chloride leave their respective carbons, allowing a bond to form between these carbons.

Step 4: Consider Intermediate Alkane Formation

The resulting radical coupling in this scenario forms a cyclobutane with an additional internal carbon bond between the 1st and 3rd positions. However, since the reaction proceeds with two molecules, two cyclobutane rings form a single ring.

Step 5: Identify The Final Product

The result of the reaction is the formation of a bicyclic hydrocarbon. Specifically, the fusion of the cyclobutanes leads to the formation of bicyclo[1.1.0]butane, a highly strained compound.

Key Concepts

1-bromo-3-chlorocyclobutane

1-bromo-3-chlorocyclobutane is an organic compound that serves as an ideal starting material in the Wurtz reaction. This molecule is a cyclobutane ring, which consists of a square arrangement of carbon atoms, adorned with two distinct halogen atoms: a bromine and a chlorine.

• The bromine atom is located at the 1-position.
• The chlorine atom resides at the 3-position.

The presence of these halides is crucial because they are reactive sites under the influence of metallic sodium. This structure sets the stage for a unique transformation where the bromine and chlorine will eventually be removed and replaced by a carbon-carbon bond, leading to more complex forms.

metallic sodium

Metallic sodium is a soft, silver-white metallic element that's known for its strong reducing properties.

• In organic chemistry, sodium is valued for its ability to donate electrons.
• These electrons are essential in breaking halogen-carbon bonds through the generation of radicals.

In the context of the Wurtz reaction, sodium's role is to facilitate the creation of carbon radicals by stripping the halogens away from the carbon skeleton. The electrons supplied by sodium allow the carbon atoms, once bound to halogens, to pair up and form a new covalent bond. This forms the backbone of the product in the reaction.

organic synthesis

Organic synthesis is a pivotal process in chemistry focused on constructing new organic molecules. In the Wurtz reaction, this synthesis allows for the formation of complex structures from simpler starting materials like 1-bromo-3-chlorocyclobutane.

• This reaction exemplifies how simple transformations can lead to significant structural changes.
• The formation of new carbon-carbon bonds is a cornerstone of synthesizing new organic molecules.

By understanding the reaction mechanism, chemists can predict the structural outcome of reactions. In this case, it provides insight into transforming 1-bromo-3-chlorocyclobutane into a bicyclic hydrocarbon. This involves coupling of radicals, a key step in moving from reactants to products in complex organic synthesis.

bicyclic hydrocarbons

Bicyclic hydrocarbons are organic compounds containing two interconnected rings of carbon atoms. They often have interesting chemical properties due to the inherent strain and stability of the bonds within the rings.

• The product of the Wurtz reaction involving 1-bromo-3-chlorocyclobutane is bicyclo[1.1.0]butane.
• This compound's structure includes two cyclobutane rings sharing two adjacent carbon atoms, forming a unique bicyclic structure.

Bicyclic hydrocarbons such as bicyclo[1.1.0]butane can exhibit high levels of ring strain, which can lead to reactivity not seen in simpler cyclic molecules. Such characteristics make them an area of interest for further research in organic chemistry.