crotylsarin crotylsarin crotylsarin (crs) is an extremely toxic organophosphate nerve agent of the g-series. like other nerve agents, crs irreversibly inhibits the acetylcholinesterase. however, since the inhibited enzyme ages so rapidly, the inhibited enzyme can't be reactivated by cholinesterase reactivators. crotylsarin names preferred iupac name (2e)-but-2-en-1-yl methylphosphonofluoridate other names crs identifiers cas number 138780-00-4 3d model (jsmol) interactive image chemspider 4943171 pubchem cid 6438716 unii y98led33gd y smiles c/c=c/cop(=o)(c)f properties chemical formula c5h10fo2p molar mass 152.105 g·mol−1 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references