🗺️ Reaction Pathways
Designing a Synthesis
Converting a starting material (feedstock) into a target molecule using a sequence of reactions.
Key Conversions
| Reaction | Reagents & Conditions | Type |
|---|---|---|
| Alkane to Halogenoalkane | $Cl_2$, UV Light | Free Radical Substitution |
| Alkene to Alcohol | $H_2O$ (Steam), $H_3PO_4$, 300°C | Hydration (Addition) |
| Alcohol to Carboxylic Acid | $K_2Cr_2O_7/H^+$, Reflux | Oxidation (Primary) |
| Halogenoalkane to Amine | Conc $NH_3$, Heat in sealed tube | Nucleophilic Substitution |
🔙 Retrosynthesis
Working backwards from the Target Molecule to simple precursors.
Strategy:
- Identify Functional Groups.
- Disconnect bonds (Carbon-Carbon bond formation is key, e.g., Grignard or Nitrile addition).
- Work back to available starting materials.
📝 Exam-Style Questions
Question 1: State the reagents and conditions required to convert Ethene to Ethanol. [1 mark]
Mark Scheme:
- [1 mark] Steam ($H_2O(g)$) and $H_3PO_4$ (Phosphoric Acid) catalyst at high temperature (300°C) and pressure.
Question 2: Outline a two-step synthesis to convert Chloroethane into Ethanoic Acid. [2 marks]
Mark Scheme:
- [1 mark] Step 1: Convert Chloroethane to Ethanol using $NaOH(aq)$, heat (Nucleophilic Substitution).
- [1 mark] Step 2: Oxidize Ethanol to Ethanoic Acid using $K_2Cr_2O_7/H^+$, Reflux.
Question 3: Deduce the product formed when Propene reacts with Hydrogen Bromide ($HBr$). Explain the major product. [2 marks]
Mark Scheme:
- [1 mark] Major product: 2-bromopropane.
- [1 mark] Markovnikov's Rule: H adds to the carbon with more hydrogens (generating the more stable Secondary Carbocation intermediate).
Question 4: Suggest a reaction scheme to convert Benzene into Phenylamine (Aniline). [2 marks]
Mark Scheme:
- [1 mark] Step 1: Nitration using Conc $HNO_3$ and Conc $H_2SO_4$ (at 50°C) to form Nitrobenzene.
- [1 mark] Step 2: Reduction using $Sn$ (Tin) and Conc $HCl$, followed by $NaOH$.
Question 5: Identify the reagents used to distinguish between an Alkane and an Alkene, and state the observation. [2 marks]
Mark Scheme:
- [1 mark] Reagent: Bromine Water ($Br_2(aq)$).
- [1 mark] Observation: Alkene turns solution from Orange to Colorless. Alkane shows No Change (remains orange) in the dark.