More than multiple choice
Drawn structures, curved arrows, retrosynthesis, spectrum interpretation, labeled diagrams, ordering, matching and more. Each one is graded by rules you can read, not by a language model’s opinion.
Chemistry problems that grade themselves.
Build problem sets with 21 question types, from drawn structures to arrow pushing. Every student gets their own version, and grading follows rules, so the same answer always gets the same mark.
Windows 10 and 11 Updates itself from the Store
Open in browser
Free for every student. No seats to buy.
Pick problems, review each one, and add the set. Any problem you do not like is one click from a new one.
Mechanism grading
Athanor pushes every curved arrow a student draws and checks that it gives the structures they drew next. A wrong step says what went wrong, and a proton transfer can be shown or left out.
What it does for your course
A different version for every student
Each student gets their own version of a problem, with different structures, so one answer does not fit another’s sheet. Answers are computed by Athanor, not written by AI. Start from scratch, from a template, or from a syllabus topic.
Assign by link, export to your LMS
Students open a link and answer in the browser, and marks land in a gradebook. A set also exports as Moodle XML or QTI 2.1 for Canvas and Blackboard, with an answer key to print.
Present with live polls
Present a document as slides and ask the room a question. Students vote or draw an answer on their phones, and you see the results as they arrive.
Plans and pricing
Every plan has the whole editor, ChemDraw files, mechanisms, 3D, problem sets with grading, collaboration and commercial use. Product prediction and routes need only a free account and never use credits.
The paid plans are one arbastro Suite subscription for every arbastro app.
- AI credits a month
- 150
- Assistant models
- Haiku and Sonnet 5.5
- Your own AI provider key
- –
- Cloud storage
- 10 MB
arbastro Suite Lite
For learning and teaching
$4.17/mo
billed $49.99 yearly · save $9.89
Start 7-day free trial
Then $4.17/mo billed yearly ($49.99), or $4.99 monthly. Cancel any time before the trial ends.
- AI credits a month
- 300
- Assistant models
- Haiku, Sonnet and Opus 5.5
- Your own AI provider key
- Cloud storage
- 100 MB
Most popular
arbastro Suite Plus
Best for active research
$16.67/mo
billed $199.99 yearly · save $39.89
- AI credits a month
- 1,000
- Assistant models
- Haiku, Sonnet and Opus 5.5, Fable 5.2
- Your own AI provider key
- Cloud storage
- 500 MB
arbastro Suite Ultra
For schools, labs and companies
$83.33/mo
billed $999.99 yearly · save $199.89
- AI credits a month
- 2,500
- Assistant models
- Haiku, Sonnet and Opus 5.5, Fable 5.2
- Your own AI provider key
- Cloud storage
- 3 GB
How Athanor compares
Swipe the table to see every tool
 Athanor | ChemDraw | ChemDoodle | Marvin | Octet Draw | Discontinued Aug 2026ChemSketch | |
|---|---|---|---|---|---|---|
| Price & access | ||||||
| Price | Free | Prime $700/yrProfessional $1,355/yr | $199/yror $999 lifetime | $29/mo academic$99/mo commercial | Free | No longer sold |
| Free for commercial work | – | – | – | – | ||
| Full editor in the browser | Enterprise plan | Developer toolkit | – | – | ||
| Prediction | ||||||
| Products predicted as you draw | – | From arrow pushing | – | – | – | |
| Retrosynthesis route planning | – | Manual disconnections | – | – | – | |
| Property prediction | Basic | |||||
| AI assistant that draws and animates | – | – | – | – | – | |
| Teaching | ||||||
| Problem sets with automatic grading | 21 question types | – | – | – | – | – |
| Mechanism checking | – | – | – | – | – | |
| Moodle XML and QTI export | – | – | – | – | – | |
| Drawing & visualization | ||||||
| 2D structure drawing | ||||||
| 3D models | – | |||||
| Orbitals and MO diagrams | Orbital palette | – | – | – | ||
| Animated mechanisms | – | – | – | – | – | |
| Biopolymers (HELM, peptides, DNA) | – | – | – | – | ||
| Data & workflow | ||||||
| Compound library with cited safety data | PubChem add‑in | – | – | – | – | |
| Live collaboration | In testing | Enterprise plan | – | – | – | – |
| Opens ChemDraw files | ||||||
| Name to structure for any IUPAC name | Online | Offline | – | |||
| Platforms | ||||||
| Desktop app | Windows | Windows, Mac | Windows, Mac, Linux | Windows, Mac, Linux | Windows | |
| Mac and Linux | In the browser | Mac | – | |||
| Works offline | Desktop app | Desktop | ||||
| Open source | – | – | – | – | Apache‑2.0 | – |
| Where others do more | ||||||
| ¹H and ¹³C NMR prediction | Predicted, AI | – | ||||
| Fully offline, no account | – | – | ||||
| Office and ELN integration | – | LabArchives | Office, on Mac | – |
Prices as of October 2026, from each vendor’s own page. Check with the vendor before you buy.
Athanor in your AI assistant
Claude, ChatGPT, Cursor and other assistants can use Athanor’s own chemistry engine through MCP: convert, name, draw and check structures, and run the safety screen. Free, with no account, and nothing stored.
The server
https://mcp-athanor.arbastro.com/mcpconvertSMILES, MOL and XYZnameIUPAC and common namespropertiesformula, masses, descriptorsdepictjournal-style drawingscheckvalence, charge, stereoscreenthe safety screenlibrary_searchAthanor’s library
In Claude Code, one line
claude mcp add --transport http athanor https://mcp-athanor.arbastro.com/mcp
A real call: name on ibuprofen’s SMILES
Asking the server…
Your data
How we handle your workLocal first, synced to your account
Screened for misuse
An open file format
FAQ
Get Athanor
Free for you and for your class. If your department cannot pay for ChemDraw seats, it does not need to.
Windows app
Windows 10 and 11. Works offline after you sign in.
Updates itself from the Store. The installer is under the arrow.
In your browser
Chrome, Edge, Firefox or Safari.
Open in browserNothing to install.