KetchDraw

A free, open-source ChemDraw alternative built with Ketcher and RDKit.js. Draw molecular structures and see calculated properties in real-time.

Features

• Ketcher Molecule Editor: Full-featured 2D molecular structure editor from EPAM
• Live Property Calculations: Properties update instantly as you draw using RDKit.js
• Structure Preview: RDKit renders SVG previews of each molecule in the properties panel
• Multiple Molecule Support: Draw multiple disconnected fragments to see properties for each
• Drug-likeness Highlighting: Properties violating Lipinski's rules are highlighted in yellow/red
• Collapsible Panel: Maximize drawing space by collapsing the properties panel
• Copy SMILES: One-click copy of SMILES strings

Calculated Properties

Property	Description
MW	Molecular Weight
cLogP	Calculated LogP (Crippen method)
TPSA	Topological Polar Surface Area
HBA	Hydrogen Bond Acceptors
HBD	Hydrogen Bond Donors
Fsp3	Fraction of sp3 carbons
RotB	Rotatable Bonds
HAC	Heavy Atom Count
Hetero	Heteroatom Count
ArRings	Aromatic Ring Count
Stereo	Defined Stereocenters
Unspec	Unspecified Stereocenters

Usage

GitHub Pages

1. Enable GitHub Pages in your repository settings
2. Set source to main branch
3. Access at https://[username].github.io/Ketchdraw

Local Development

Serve via a local HTTP server (required for iframe to work):

# Python 3
python -m http.server 8000

# Node.js
npx serve

Then visit http://localhost:8000

Drawing Tips

• Click and drag to draw bonds
• Use the element toolbar to change atom types
• Use templates for common ring structures
• Draw disconnected fragments for multiple molecules
• Use the eraser tool or select and delete to remove atoms/bonds

Drug-Likeness Rules (Lipinski's Rule of Five)

Properties are color-coded based on oral bioavailability guidelines:

• Green: Within guidelines
• Yellow: Approaching limits
• Red: Exceeds limits

Property	Warning	Alert
MW	>450	>500
cLogP	>4	>5
TPSA	>120	>140
HBA	>8	>10
HBD	>4	>5
RotB	>7	>10

Technology Stack

• Ketcher - Molecular structure editor by EPAM
• RDKit.js - Cheminformatics toolkit for JavaScript

License

MIT License - free to use and modify.

Acknowledgments

• EPAM for the excellent Ketcher editor
• RDKit community for the JavaScript/WebAssembly port