Question

Using your reaction roadmap as a guide, show how to convert 2-methylpentane into 2-methyl-3-pentanone. Show all reagents needed and all molecules synthesized along the way.

Short answer

Answer: The sequence of reactions and reagents to convert 2-methylpentane to 2-methyl-3-pentanone are: 1. Hydroboration-oxidation using BH3, followed by H2O2 and OH- to form 2-methylpentan-3-ol. 2. Oxidation using Pyridinium Chlorochromate (PCC) to convert 2-methylpentan-3-ol into 2-methyl-3-pentanone.

Step-by-step solution

Oxidize primary alcohol to an aldehyde

We need to first convert the 2-methylpentane into 2-methylpentan-3-ol by adding an OH group at the 3rd carbon. For this reaction, we use hydroboration-oxidation (\text{BH}_3, then H_2O_2 and OH^-). The reaction proceeds as follows: 2-methylpentane + \text{BH}_3 \rightarrow 2-methylpentan-3-ol (intermediate) 2-methylpentan-3-ol (intermediate) + H_2O_2 + OH^- \rightarrow 2-methylpentan-3-ol

Oxidize the aldehyde to a ketone

Now, we need to convert the aldehyde (2-methylpentan-3-ol) to a ketone (2-methyl-3-pentanone). For this, we use PCC (\text{PyridiniumChloroChromate}) as oxidizing agent: 2-methylpentan-3-ol + \text{PCC} \rightarrow 2-methyl-3-pentanone In summary, the entire transformation from 2-methylpentane to 2-methyl-3-pentanone involves two main steps with the following reagents: 1. Hydroboration-oxidation (\text{BH}_3, then H_2O_2 and OH^-) 2. PCC oxidation (Pyridinium Chlorochromate) The final product is 2-methyl-3-pentanone.