Back to: Organic Chemistry 300 Level
Welcome to class!
Hello genius! Today, we will be talking about something every organic chemist must master — how to think ahead and plan the making of a molecule. Just like building a house, you don’t just start putting bricks together; you need a clear plan, the right materials, and a step-by-step approach. In chemistry, this is called synthetic planning and strategy — the art of designing a logical, efficient pathway to create a target molecule.
Synthetic Planning & Strategy
Meaning of Synthetic Planning
Synthetic planning is the process of working backwards from a target molecule to simpler, available starting materials and deciding the sequence of reactions to get there. It is also known as retrosynthetic analysis.
Key Concepts in Synthetic Strategy
Target Molecule (TM): The compound you want to make.
Retrosynthesis: Breaking the TM down into simpler precursors by mentally “undoing” reactions.
Synthons: Idealised fragments representing parts of the TM in retrosynthesis.
Reagents: Real chemicals that provide the synthons in practice.
Functional Group Interconversion (FGI): Changing one functional group into another as part of the plan.
Approaches to Planning
Linear Synthesis: Steps are carried out one after the other, each producing an intermediate for the next.
Convergent Synthesis: Separate parts of the molecule are prepared independently and then joined together. This saves time and can increase yield.
Important Considerations
Step Economy: Fewer steps mean less cost, less waste, and better yield.
Selectivity: Plan reactions so that only the desired product is made (chemoselectivity, regioselectivity, stereoselectivity).
Availability of Starting Materials: Choose starting materials that are cheap and accessible.
Reaction Conditions: Ensure that conditions are compatible for sensitive functional groups.
If your target molecule is methyl benzoate:
Retrosynthesis suggests an esterification between benzoic acid and methanol.
Benzoic acid can come from the oxidation of toluene.
Plan: Toluene → oxidation → benzoic acid → esterification with methanol → methyl benzoate.
In pharmaceutical production in Nigeria, synthetic planning is used to make active ingredients from locally available raw materials like essential oils, cassava-derived ethanol, or palm kernel oil derivatives.
Summary
- Synthetic planning is the design of a logical pathway from starting materials to a target molecule.
- Retrosynthesis involves mentally breaking a molecule into simpler building blocks.
- Linear synthesis proceeds step-by-step; convergent synthesis builds separate parts before combining them.
- Good strategy considers step economy, selectivity, cost, and availability of materials.
- Synthetic planning is vital in research, pharmaceuticals, and industrial chemistry in Nigeria.
Evaluation
- Define synthetic planning.
- What is retrosynthesis?
- List three important considerations in designing a synthesis.
- Differentiate between linear and convergent synthesis.
- Give one Nigerian example of synthetic planning in industry.
You’ve just gained the mindset of a master chemist — one who can think ahead, design a pathway, and turn an idea into reality. With Afrilearn, you are building skills that open doors to scientific innovation and industrial success.