Question

Using your reaction roadmap as a guide, show how to convert 4 -methyl-1-pentene into 5-methylhexanenitrile.You must use 4 -methyl-1-pentene and sodium cyanide as the source of all carbon atoms in the target molecule. Show all reagents needed and all molecules synthesized along the way.

Short answer

Question: Outline a step-by-step procedure to convert 4-methyl-1-pentene into 5-methylhexanenitrile using sodium cyanide. Answer: The conversion of 4-methyl-1-pentene to 5-methylhexanenitrile can be achieved through the following steps: 1. Hydrogenation: Treat 4-methyl-1-pentene with H2 and Pd/C catalyst at room temperature and atmospheric pressure to convert the double bond into a single bond, yielding 4-methylpentane. 2. Radical Bromination: React 4-methylpentane with N-bromosuccinimide (NBS) and azobis(isobutyronitrile) (AIBN) under reflux conditions to form 5-bromo-4-methylpentane. 3. Nitrile synthesis: Treat 5-bromo-4-methylpentane with sodium cyanide (NaCN) under reflux with an aprotic solvent to introduce the CN group, yielding the final product, 5-methylhexanenitrile.

Step-by-step solution

Analyze the structures of the starting material and the target molecule

Starting material: 4-methyl-1-pentene (CH3CH=C(CH3)CH2CH3) Target molecule: 5-methylhexanenitrile (CH3CH2CH2CH(CN)(CH3)CH3) Comparing these two structures, we can see that we need to: 1. Add 1 carbon to the carbon chain 2. Transform the carbon-carbon double bond in 4-methyl-1-pentene into a single bond 3. Introduce a nitrile (CN) group in the target molecule

Convert the double bond into a single bond

To convert the double bond into a single bond, we can perform hydrogenation of 4-methyl-1-pentene. Reagents: H2 and Pd/C as a catalyst Conditions: Room temperature and atmospheric pressure This reaction will yield 4-methylpentane (CH3CH2C(CH3)CH2CH3).

Add the CN group

To introduce the cyanide group, we can perform nitrile synthesis using sodium cyanide (NaCN). Reagents: NaCN and a suitable alkyl halide (R-X) Conditions: Reflux with an aprotic solvent First, we need to convert the 4-methylpentane to an alkyl halide (e.g., Bromo derivative) by performing a radical halogenation in allylic position. Reagents: N-bromosuccinimide (NBS) and azobis(isobutyronitrile) (AIBN) as a radical initiator Conditions: Heating the reaction mixture under reflux This reaction will yield 5-bromo-4-methylpentane (CH3CH2C(Br)C(CH3)CH2CH3). Now, we can perform the nitrile synthesis using sodium cyanide: 5-bromo-4-methylpentane + NaCN ⟶ 5-methylhexanenitrile + NaBr This reaction will yield 5-methylhexanenitrile (CH3CH2CH2CH(CN)(CH3)CH3) as the final product. So, the sequence of reactions is: 1. Hydrogenation: 4-methyl-1-pentene + H2/Pd/C → 4-methylpentane 2. Radical Bromination: 4-methylpentane + NBS/AIBN → 5-bromo-4-methylpentane 3. Nitrile synthesis: 5-bromo-4-methylpentane + NaCN → 5-methylhexanenitrile