The Best Ways of Answering Chemistry Synthesis Pathway Questions in A-Level Chemistry

Synthesis pathway questions are a core skill in A-Level Chemistry – and one that many students find intimidating. Multiple steps, unfamiliar reagents, and the fear of “missing the right reaction” can quickly derail an answer.

The good news? These questions are highly structured and reward methodical thinking, not flashes of inspiration. Here’s how to tackle them with confidence.

1. Start With the Functional Groups (Not the Reagents)

Before thinking about chemicals or conditions, circle the functional groups in:

The starting compound
The final target molecule

Ask:

What has been added?
What has been removed?
What has been oxidised or reduced?

Most synthesis questions are really asking:

How do I convert one functional group into another, step by step?

2. Think in Small, Logical Steps

A common mistake is trying to jump straight from start to finish.

Instead:

Break the pathway into single functional-group changes
Insert obvious intermediates, even if the question doesn’t show them

For example:

Alkane → haloalkane → alcohol → aldehyde → carboxylic acid
Each arrow is one familiar reaction.

Examiners expect intermediate compounds to appear.

3. Use Your “Core Reactions” Toolbox

Most A-Level synthesis pathways rely on a small set of reactions used repeatedly:

Substitution (e.g. halogenoalkanes)
Elimination (alkene formation)
Addition (alkenes → alcohols)
Oxidation (alcohols → aldehydes / acids)
Reduction (carbonyls → alcohols)
Nucleophilic addition (carbonyl chemistry)

If you revise these as building blocks, synthesis questions become much easier to decode.

4. Always State Reagents AND Conditions

Marks are often split:

1 mark for the reagent
1 mark for the condition (heat, reflux, catalyst, solvent)

Examples:

“Acidified potassium dichromate(VI), reflux”
“Concentrated sulfuric acid, heat”
“Aqueous sodium hydroxide, warm”

A correct reagent with missing conditions can lose you marks.

5. Watch for Carbon Skeleton Changes

Ask yourself:

Does the number of carbons change?
Is a CN group added (carbon chain length +1)?
Is a molecule cracked or rearranged?

Carbon-chain extension reactions are classic exam traps and usually involve:

Cyanide ions
Nitriles followed by hydrolysis

6. Use Clear, Logical Layout

Your answer should look like a route map, not a paragraph.

Best practice:

Draw each structure clearly
One reaction per arrow
Reagents written above or below arrows
Avoid crossing arrows or messy layouts

Examiners reward clarity of chemical thinking.

7. If Stuck, Work Backwards

If the forward route isn’t obvious:

Start from the final product
Ask “what could this come from?”
Reverse-engineer the pathway

This often reveals a familiar last step (oxidation, reduction, addition) that unlocks the whole question.

Final Thought

Synthesis pathway questions are less about memory and more about pattern recognition and structured problem-solving. With practice, students move from “I have no idea” to “I know exactly where to start”.

If you can:
✔ Identify functional groups
✔ Apply core reactions
✔ Lay answers out clearly

…you are already most of the way to top-band marks.

09 January 2026