Retrosynth

You work backwards from a target molecule, choosing transformations that break it into simpler pieces until you reach materials you are allowed to start from. This is a game abstraction of retrosynthesis rather than a chemistry tool — the functional groups and reaction rules are a simplified scheme built for play, loosely inspired by the real discipline.

• Each step goes backwards: you pick a disconnection that would have produced what you are holding.
• Transformations are gated by the mechanism they represent, so not every rule applies to every molecule.
• The scheme is curated and deliberately smaller than real organic chemistry.
• Puzzles are seeded, so the same target always breaks down the same way.
• It is designed to teach the SHAPE of retrosynthetic thinking rather than the content of a chemistry course.

• Desktop: click an option to take a retro step, click a partner when prompted, and use Hint if stuck; choose Daily/Practice and a difficulty.
• Phone & tablet: tap options and partners, fully touch-friendly.

• Look for the bond that most simplifies the skeleton; the best disconnection usually splits the molecule near the middle.
• Match each functional group to the role it plays before choosing its mechanism partner.
• Fewer steps beats par, avoid disconnections that lead away from anything on the shelf.

Retrosynth captures the backward-planning logic of retrosynthetic analysis, the organic chemist's craft.

• Skills: organic chemistry, retrosynthesis, backward planning
• Best for: advanced high school / college
• For parents & teachers: retrosynthesis, the organic chemist's logic.

Working backwards from a target molecule by breaking it into simpler pieces until you reach permitted starting materials is retrosynthetic analysis, the planning method E. J. Corey formalised.

Running it strictly backwards is the original discipline.

Backwards is the direction that makes synthesis tractable. Working forwards from reagents is an unbounded search; working back from the target means each disconnection is chosen for what it simplifies, which is why the method won a Nobel Prize and why chemists still plan on paper this way.

Retrosynth captures the backward-planning logic that organic chemists call retrosynthetic analysis, turning it into a tidy step-count puzzle. It's an original, free browser game with three difficulties and daily plus practice modes.

A free, original browser game on PlayPendium. No download, no install.