Question

Show how spiro[2.2]pentane can be prepared in one step from organic compounds containing three carbons or fewer and any necessary inorganic reagents or solvents.

Short answer

Answer: Spiro[2.2]pentane can be synthesized in one step by performing an intramolecular Wurtz coupling reaction using 1,3-dibromopropane as the starting material and sodium metal as the reagent. The balanced reaction equation is: BrCH2CH2CH2Br + 2Na -> Spiro[2.2]pentane + 2NaBr.

Step-by-step solution

Identify the starting compound and the reagents

First, let's identify the starting compound and reagents that we can use to synthesize spiro[2.2]pentane. One possibility is to use 1,3-dibromopropane as the starting material by performing an intramolecular Wurtz coupling reaction using sodium metal as the reagent. The structure of 1,3-dibromopropane is BrCH2CH2CH2Br.

Write the reaction equation

We will now write the balanced equation for the reaction between 1,3-dibromopropane and sodium metal to form spiro[2.2]pentane. In this intramolecular Wurtz coupling reaction, two bromine atoms are replaced by a single bond between two carbons. The balanced reaction equation is as follows: BrCH2CH2CH2Br + 2Na -> Spiro[2.2]pentane + 2NaBr Thus, spiro[2.2]pentane can be prepared in one step from 1,3-dibromopropane and sodium metal.

Key concepts

Intramolecular Wurtz Coupling Reaction

When we delve into the fascinating world of organic chemistry, the intramolecular Wurtz coupling reaction emerges as a compelling method for creating cyclic structures. This reaction represents a subtype of the general Wurtz coupling process, which involves the formation of a new carbon-carbon bond.

Imagine the Wurtz reaction as a dance between carbon atoms and a metal, typically sodium. The metal donates electrons that help carbon atoms in a molecule, like wallflowers at a dance, come together to form a bond. In the intramolecular version, the bonding happens within a single molecule, causing it to fold onto itself and couple, much like how a dancer might spin into a twist.

This occurs when a molecule, such as 1,3-dibromopropane, contains two reactive sites facing each other, both inviting the sodium to initiate the coupling. When sodium steps in, it effectively removes the bromine atoms, facilitating a carbon-carbon bond formation within the molecule, which results in a cyclic structure, such as spiro[2.2]pentane.

1,3-Dibromopropane

One of the key players at the heart of this process is 1,3-dibromopropane, a small but versatile organic compound consisting of a three-carbon chain flanked by bromine atoms on each end. These bromine atoms spark the interest of sodium metal, making 1,3-dibromopropane an attractive starting point for the synthesis of more complex molecules through halogen-metal exchange reactions.

In the context of creating spiro compounds, the structural layout of 1,3-dibromopropane is ideal. It's like having a neatly set stage where all actors are in place for the action—the intramolecular Wurtz coupling—to unfold. Not only does the presence of bromine atoms make it reactive, but the positioning of these atoms allows for the intriguing transformation into a spiro compound, carrying us into a rapidly advancing area of organic synthesis.

Organic Synthesis Methods

The study of organic synthesis methods is akin to exploring a toolbox filled with techniques for constructing a multitude of organic compounds. Each method offers a unique approach, with the Wurtz reaction being just one amongst an array of strategies.

Many of these methods are based on functional group manipulations, such as halogen-metal exchanges, oxidations, reductions, and more. In the synthesis of spiro[2.2]pentane, we leverage the muscle power of sodium to perform an elimination-type reaction, where the loss of bromine atoms is compensated by the formation of a new bond.

In a broader perspective, organic synthesis encompasses not only the direct transformations but also the design principles. It's about predicting how molecules will behave under various conditions and guiding them to form new structures, aiming for high yields, selectivity, and efficiency. This discipline is crucial for advancing many areas, such as pharmaceuticals, materials science, and biochemistry, reflecting how these methods are instrumental in creating molecules that can better our world.