XDrawChem

XDrawChem is a free software program for drawing chemical structural formulas, available for Windows, Unix, and Mac OS. It is distributed under the GNU GPL.

Major features

* Fixed length and fixed angle drawing
* Automatic alignment of figures
* Detection of structures, text, and arrows, and their automatic placement
* Can automatically draw rings and other structures - has all standard amino acids and nucleic acids in a built-in library
* Retrieval of structures from a network database based on CAS number, formula, or name
* Retrieval of information on a molecule based on a drawing
* Symbols such as partial charge and radicals
* Reading MDL Molfiles, CML (Chemical Markup Language), ChemDraw binary format, ChemDraw XML text format
* Writing MDL Molfiles, CML, ChemDraw XML text format
* Integration with OpenBabel, allowing XDrawChem to read and write over 20 different chemical file formats.
* Image export in Portable Network Graphics (PNG), Windows bitmap, Encapsulated PostScript (EPS), and Scalable Vector Graphics (SVG)
* 3D structure generation with the help of the external program BUILD3D
* Simple spectra predictions, including 13C-NMR, 1H-NMR (based on additive rules and functional group lookup methods), and IR
* Simple property estimation, including pKa, octanol-water partition coefficient, and gas-phase enthalpy change.