ppchtex – Typeset chemical formula diagrams
ppchTeX is a separate module of the ConTeXt macro package for TeX. It seems to be in its final state (having not changed for more than 10 years).
Maybe you are interested in the following packages as well.
- chemcompounds: Simple consecutive numbering of chemical compounds
- chemstruct: Structural organic chemistry
- streetex: Structural organic chemistry
- chemstyle: Writing chemistry with style