XDrawChem is a free software program for drawing chemical structural formulas, available for Unix and macOS. It is distributed under the GNU GPL. In Microsoft Windows this program is called WinDrawChem.
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.