PVC is not "vinyl"

[ttweed@wildrockies.org (Tony Tweedale)]

occassionally, as now (Fall '99, p.5), I see PVC referenced as "vinyl".
This is a confusing and inaccurate conflation of the one chemical and a
class of chemicals that don't involve chlorine.  So (everyone), if you're
trying to let people know that PVC is a chlorinated organic nasty, tag it
w/ the label that displays the wordstem "chlor/o", and abandon the mistaken
identifier 'vinyl'.

According to my dictionary (I looked this up years ago for precisely the
reason above, as I was confused about the conflation), "vinyl" means either
the univalent 'vinyl group', or a polymer containing the that vinyl group.
It is:

2H-C=C-

Note its second C has an unfilled valence shell (univalent), so it is
looking to react w/ something, and that's why it polymerizes so nicely (I'm
assuming--never read up on it).  Note Cl is nowhere in sight.  As I recall,
vinyl chloride monomer (2H-C=C-Cl) is usually made via salt (NaCl -> Cl2
(gas) -> substitution of saturated HC's -> perchlorethene (2Cl-C=C-Cl2, aka
tetrachlorethene) -> VC; rather than directly from the vinyl group serving
as a monomer.  But in any case, 'vinyl' or vinyl polymers ain't synonymous
w/ chlorinated--e.g. vinyl acetate, vinyl ether, etc.

Despite my uncertainty (above) of the vinyl group being directly involved
in polymerizing VC, I also wonder if the polymer vinylidene chloride
(2H-C=C-Cl2, Saran wrap and other applications) has one extra chlorine per
monomer because the vinylidene group is bivalent: 2H-C=C=
Hmmnnn...anyone?

Tony Tweedale

Causality is a concept not subject to empirical demonstration. -David Hume
(1711-'76)

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