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: The single-step synthesis of spiro[2.2]pentane involves starting with cyclopropanone (C_3H_4O) as the organic compound containing three carbons or fewer. The reagent used is methyllithium (CH_3Li), which reacts with the carbonyl group of cyclopropanone to form the desired spiro compound.

Step-by-step solution

Identify starting materials

As mentioned in the analysis, we will use cyclopropanone (C_3H_4O) as our starting organic compound, since it contains three carbon atoms. This compound will be the basic structure from which spiro[2.2]pentane will be formed.

Choose an appropriate reagent

To synthesize spiro[2.2]pentane in a single step, we need a powerful reagent that can induce a reaction to form the desired bicyclic structure. One such reagent is methyllithium (CH_3Li), which is known to be highly reactive. Methyllithium is an organolithium compound, and these compounds are often used in organic synthesis due to their strong nucleophilic properties.

Perform the reaction

Now, combine cyclopropanone and methyllithium in a solvent that can stabilize both reagents, such as diethyl ether. The methyllithium will react with the carbonyl group of cyclopropanone, leading to the formation of a lithium alkoxide. This lithium alkoxide is a strong nucleophile, which then attacks the other carbon atom of the carbonyl group, causing the formation of a new carbon-carbon bond, resulting in the production of spiro[2.2]pentane and the release of a lithium hydroxide molecule (LiOH). The overall reaction can be represented as follows: C_3H_4O (cyclopropanone) + CH_3Li (methyllithium) -> C_5H_8 (spiro[2.2]pentane) + LiOH (lithium hydroxide)

Isolate the product

Once the reaction is complete, separate spiro[2.2]pentane from the mixture. This can be done by adding water to the reaction mixture, which will quench any remaining organolithium reagent and form a precipitate of lithium hydroxide. Filter the mixture to remove this precipitate, and then extract the organic layer containing the spiro[2.2]pentane. Finally, evaporate the solvent to obtain pure spiro[2.2]pentane as the final product.