Re: Drawing Lewis structures

 Disclaimer: I am a mathematician, not a chemist.
 Ron A. Rumley- Van Gurp writes:
 >We are looking for software (Linux/Windows95/98 or NT) that can draw Lewis
 >structures of organic molecules, depicting all electron lone  pairs as well
 >as bonding pairs. Is there any computer program  available that generates
 >such structures semi-automatically?
 I asked about this several years ago. At the time, people referred
 me to ChemTeX, which draws chemical formulas, but it doesn't seem
 to handle Lewis structures. In Latex, one could probably use the
 resident graphics capabilities to write macros or enhance the ones
 that come with ChemTeX. If I were to do it, I would probably write
 some programs directly in PostScript, but that is a matter of taste
 and endurance.
 Does "semi-automatically" imply that the program will figure out the
 Lewis structure as well as draw it? The problem with that, in
 my perception, is that, at least as it is described in textbooks,
 the procedures for determining Lewis structures are not consistent.
 There is an exception in the case of books which dumb down the rules
 to apply only to a small class of examples (the "This is a course on
 how to pass this course" approach), but let's not even mention that.
 People have been complaining about this all the way back to Lewis, who
 never intended that his innovation should be used to prop up the same
 kind of arbitrary rule-based pedagogy about bonding that he himself had
 to go through and which he had hoped to dispel by inventing Lewis structures.
 I have a list somewhere, guaranteed not to be complete, which I compiled
 when I was thinking of writing an article about how screwed up pedagogy
 seems to be on this point. I abandoned the project when I realized that
 people have long complained about this in print and it has had no effect
 whatsoever on pedagogical practice.
 Apart from such inconsistencies, different authors try to do different
 things with Lewis structures. For example, Wheland's book on resonance
 has much fancier versions of Lewis structures with different kinds of
 electrons, and if I remember correctly he refers to other literature
 that I was unable to obtain that takes it even further. At any rate,
 there seem to be a lot of versions of "Lewis structures" in the
 literature.
 Allan Adler
 adler at.at hera.wku.edu