Chemical Warfare

Chem Warfare
It was not until the early 1930\'s that German
chemists observed that organo-phosphorus
compounds could be poisonous. In 1934, Dr
Gerhard Schrader, a chemist at IG Farben, was
given the task of developing a pesticide. Two
years later a phosphorus compound with
extremely high toxicity was produced for the first
time. According to contemporary regulations,
discoveries with military implications had to be
reported to the military authorities, which was also
done with Schrader\'s discovery. This phosphorus
compound, given the name tabun, was the first of
the substances later referred to as nerve agents. A
factory for production of the new CW agent was
built and a total of 12 000 tonnes of tabun were
produced during the years 1942-1945. At the end
of the war the Allies seized large quantities of this
nerve agent. Up to the end of the war, Schrader
and his co-workers synthesized about 2 000 new
organo-phosphorus compounds, including sarin
(1938). The third of the "classic" nerve agents,
soman, was first produced in 1944. These three
nerve agents are known as G agents in the
American nomenclature. The manufacture of sarin
never started properly and up to 1945 only about
0.5 tonne of this nerve agent was produced in a
pilot plant. Immediately after the war, research
was mainly concentrated on studies of the
mechanisms of the nerve agents in order to
discover more effective forms of protection against
these new CW agents. The results of these efforts
led, however, not only to better forms of
protection but also to new types of agents closely
related to the earlier ones. By the mid-1950\'s a
group of more stable nerve agents had been
developed, known as the V-agents in the
American nomenclature. They are approximately
ten-fold more poisonous than sarin and are thus
among the most toxic substances ever synthesized.
The first publication of these substances appeared
in 1955. The authors, R. Ghosh and J.F.
Newman, described one of the substances, known
as Amiton, as being particularly effective against
mites. At this time, intensive research was being
devoted to the organo-phosphorus insecticides
both in Europe and in the United States. At least
three chemical firms appear to have independently
discovered the remarkable toxicity of these
phosphorus compounds during the years
1952-53. Surprisingly enough, some of these
substances were available on the market as
pesticides. Nonetheless, they were soon
withdrawn owing to their considerable toxicity also
to mammals. In the United States, the choice fell in
1958 on a substance known by its code name VX
as suitable as a CW agent of persistent type.
Full-scale production of VX started in April 1961
but its structure was not published until 1972.
Physical and Chemical Properties The most
important nerve agents included in modern CW
arsenals are: ? Tabun, O-ethyl
dimethylamidophosphorylcyanide, with the
American denomination GA. This nerve agent is
the easiest to manufacture. Consequently, it is
more likely that developing countries start their
CW arsenal with this nerve agent whereas
industrialized countries consider tabun to be
out-of-date and of limited use. ? Sarin, isopropyl
methylphosphonofluoridate, with the American
denomination GB, a volatile substance mainly
taken up through inhalation. ? Soman, pinacolyl
methylphosphonofluoridate, with the American
denomination GD, a moderately volatile substance
which can be taken up by inhalation or skin
contact. ? Cyclohexyl methylphosphonofluoridate,
with the American denomination GF, a substance
with low volatility which is taken up through skin
contact and inhalation of the substance either as a
gas or aerosol. ? O-ethyl
S-diisopropylaminomethyl
methylphosphonothiolate, better known under the
American denomination VX, a persistent
substance which can remain on material,
equipment and terrain for long periods. Uptake is
mainly through the skin but also through inhalation
of the substance as a gas or aerosol. The formulae
for some nerve agents are: ? Tabun, GA:
(CH3)2N-P(=O)(-CN)(-OC2H5) ? Sarin, GB:
CH3-P(=O)(-F)(-OCH(CH33)2) ? Soman, GD:
CH3-P(=O)(-F)(-CH(CH3)C(CH3)3 ? GF:
CH3-P(=O)(-F)(cyklo-C6H11) ? VX:
CH3-P(=O)(-SCH2CH2N[CH(CH3)2]2)(-OC2H5)

Category: Science