3-PAM and 4-PAM are meta and para positioned oxime groups with respect to the pyridinium methyl group respectively. The dodecyliodide of 2-PAM is PAD, the methylchloride is PAC,the methane sulfonate is P2s/contrathion less effective than 2-PAM or 4-PAM
Title: Reactivation of model cholinesterases by oximes and intermediate phosphyloximes: a computational study Vyas S, Hadad CM Ref: Chemico-Biological Interactions, 175:187, 2008 : PubMed
Phosphyloximes (POX) are generated upon the reactivation of organophosphorus (OP)-inhibited cholinesterases (ChEs) by pyridinium oximes. These POXs are known to be potent inhibitors of the ChEs following reactivation. However, they can also decompose to give an OP derivative and a cyano derivative of the oxime when a base abstracts the benzylic proton. Using density functional theory, thermodynamic properties were calculated for the reactivation and decomposition pathways of three different oximes (2-PAM, 3-PAM and 4-PAM) with six different OPs (cyclosarin, paraoxon, sarin, tabun, VR and VX). For reactivation purposes, 2-PAM is predicted to be more efficient than 3- and 4-PAM. Based on atomic charges and relative energies, 2-POXs were found to be more inclined towards the decomposition process.
