Draw organic chemistry reaction mechanisms online, free
Arrow Lab's mechanism editor is a free online tool for arrow pushing: place atoms, bonds and rings, draw curved electron arrows one step at a time, then press Solve it to check every arrow with instant feedback. Nothing to install and no account; your mechanisms are saved in this browser. Free for a limited time.
How to draw a mechanism
- Start with the starting material: pick a template from My mechanisms, or draw it by hand with the Atom, Bond, Chain and Ring tools (type a symbol such as O, N or Br while pointing at an atom to relabel it).
- Choose the Arrow tool and drag each curved arrow from the electron source (a lone pair or a bond) to its destination (an atom, a bond, or the midpoint of a new bond).
- Press Next step: the editor applies your arrows and shows the intermediate or product they produce; fix anything it got wrong, or draw it yourself. Repeat for every step of the mechanism.
- Press Solve it to replay your mechanism as a student would: drag the electrons yourself and get feedback on every arrow.
- Open Diagnostics for a list of octet, formal-charge and lone-pair problems in each structure, with a link to the atom or bond to fix.
What the editor checks
Every structure is checked as a Lewis structure: octets, formal charges, lone pairs and unpaired electrons, plus wedges and dashes that cannot mark a real stereocenter. Every curved arrow is checked for a valid electron source and destination, and Solve it compares the arrows you draw against the arrows you authored. The editor does not judge whether a mechanism is chemically reasonable; that part stays with you.
Check your real homework, arrow by arrow
Snap a photo of a mechanism from your homework and Arrow Lab turns it into a step-by-step mechanism you solve on screen, with feedback on every arrow you draw: the same check as Solve it, on your actual assignment. 1 free scan now, no sign-up; 1 more with a free account.
Questions
Is the mechanism editor free?
Yes. The editor is free for a limited time, with no account and no sign-up: open the page and start drawing.
Where are my mechanisms saved?
In this browser, on this device, through its local storage. They are not sent to a server. Clearing the site's data in your browser deletes them, so keep a photo or export of anything you need to keep.
Can it check my mechanism?
Yes. Solve it replays your mechanism as an exercise and gives feedback on every curved arrow. Diagnostics flags octet, formal-charge and lone-pair problems and broken arrows in every structure you draw.
Does it work on a phone?
Yes. The editor works with touch: tap to place atoms and drag to draw bonds and arrows. A tablet or laptop screen is easier for larger mechanisms.
What is Scan Standard?
Scan Standard is Arrow Lab's monthly subscription: photograph a handwritten mechanism and get a step-by-step mechanism to solve on screen, arrow by arrow, plus this editor. Current monthly prices are on the pricing page.