LaTeX can be used to typeset many kinds of different documents, but
typesetting chemical reactions is esthetically not very pleasing because
LaTeX's own arrows \rightarrow, \leftarrow and \rightleftharpoons which
you might use for this purpose are too short and the arrow heads are not
like the "standard" ones you will find in books or journals on chemistry.

The macro chemarrow.sty in conjunction with the font arrow.mf is supposed
to make the typesetting of chemical reaction schemes in LaTeX easier and
especially nicer looking.