Question

Using your 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

Question: Describe the steps to convert 2-methylpentane into 2-methyl-3-pentanone. Answer: To convert 2-methylpentane into 2-methyl-3-pentanone, three main steps are involved: 1. Perform a radical halogenation using N-bromosuccinimide (NBS) and a radical initiator to form 2-bromo-2-methylpentane. 2. Carry out a nucleophilic substitution using water (H₂O) and potassium hydroxide (KOH) to replace the bromine atom with a hydroxyl group (OH), forming 2-methyl-2-pentanol. 3. Finally, oxidize the 2-methyl-2-pentanol using potassium permanganate (KMnO₄) in an alkaline medium, such as sodium hydroxide (NaOH), to produce the desired ketone, 2-methyl-3-pentanone.

Step-by-step solution

Formation of 2-methyl-2-pentanol from 2-methylpentane

To achieve this, we need to perform a radical halogenation of the 2-methylpentane with N-bromosuccinimide (NBS) and a suitable radical initiator (heat or sunlight). This reaction will substitute a bromine atom at the tertiary carbon, giving us 2-bromo-2-methylpentane. Reaction: 2-methylpentane + NBS -> 2-bromo-2-methylpentane

Formation of 2-methyl-2-pentanol

Next, we need to perform a nucleophilic substitution with water (H₂O) to replace the bromine atom with a hydroxyl group (OH). We can use a strong base such as potassium hydroxide (KOH) to facilitate this reaction. As a result, we obtain 2-methyl-2-pentanol. Reaction: 2-bromo-2-methylpentane + KOH + H₂O -> 2-methyl-2-pentanol + KBr

Formation of 2-methyl-3-pentanone

Finally, we need to oxidize the 2-methyl-2-pentanol to produce the ketone, 2-methyl-3-pentanone. We can use an oxidizing agent like potassium permanganate (KMnO₄) in an alkaline medium, such as sodium hydroxide (NaOH), for this reaction. Reaction: 2-methyl-2-pentanol + KMnO₄ + NaOH -> 2-methyl-3-pentanone + MnO₂ + H₂O + K₂SO₄ + Na⁺ Overall, the conversion of 2-methylpentane into 2-methyl-3-pentanone involves a radical halogenation followed by a nucleophilic substitution and then an oxidation of the resulting alcohol to a ketone.