Cyclosarin

Cyclosarin or GF (cyclohexyl methylphosphonofluoridate) is an extremely toxic substance that is one of the world's most dangerous weapons of war. It is a member of the G-series family of nerve agents, a group of chemical weapons discovered and synthesized by a German team led by Dr. Gerhard Schrader. The major nerve gases are the G agents, sarin (GB), soman, tabun, and the V agents such as VX. The original agent, tabun, was discovered in Germany in 1936 in the process of work on organophosphorus insecticides. Next came sarin, soman and finally the most toxic, VX, a product of commercial insecticide laboratories prior to World War II.

As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations, according to UN Resolution 687, and its production and stockpiling was outlawed by the Chemical Weapons Convention of 1993.

Chemical characteristics
Like its predecessor sarin, cyclosarin is a liquid organophosphate nerve agent. Its physical characteristics are quite different from sarin, however.

At room temperature, cyclosarin is a colorless liquid whose odor has been variously described as sweet and musty, or resembling peaches or shellac. Unlike sarin, cyclosarin is a persistent liquid, meaning that it has a low vapor pressure and therefore evaporates relatively slowly, about 69 times more slowly than sarin and 20 times more slowly than water.

Also unlike sarin, cyclosarin is flammable, with a flash point of 94°C (201 °F).

Historical notes
From CBWInfo.com


 * Cyclosarin was first synthesized during World War II as part of the systematic study of organophosphates undertaken by the Germans after their potential military utility was identified. It was again looked at in the early 1950's by both the United States and Great Britain as they undertook a systematic study of potential nerve agents (some U.S. sources suggest that interest in GF was stimulated by work undertaken in "another country"). However, the higher cost of the precursors for GF relative to those for GB along with its lower toxicity prevented it from being chosen for manufacture.


 * Iraq is the only country in which large amounts of cyclosarin have ever been produced for use as a chemical warfare agent. Also Iraqis used sarin and cyclosarin as a mixture against Iran in 1986-1988. As with most issues surrounding the Iraqi chemical weapons programs, the basis for their decision to produce GF is somewhat unclear. However, it seems likely that the choice was driven by a combination of a desire for a more persistent agent combined with problems with obtaining alcohol precursors for sarin (due to an embargo).


 * As noted above, Iraq also fielded weapons filled with mixtures of sarin and cyclosarin. These mixtures appear to have been produced in part for purposes of increasing persistence and in part because of raw material issues.

Binary weapons
Like other nerve agents, cyclosarin can be shipped in binary munitions.

A cyclosarin binary weapon would most likely contain methylphosphonyldifluoride in one capsule, with the other capsule containing either cyclohexanol or a mixture of cyclohexylamine and cyclohexanol.

GB-GF Mixtures
According to CBWInfo.com, Iraq fielded munitions filled with a mixture of GB (sarin) and GF (cyclosarin). Tests on mice indicated that GB-GF mixtures have a relative toxicity between GF and GB.