The examination of spectra of a selected series of phosphoramidates showed that, in addition to a double bond, whenever there are one or two partial multiple bonds in the molecule the long-range coupling constant, such as 6 J P -H , 7 J P -H and 3 J P -H , either disappears or at least reduces. In particular, the experimental data indicate the unexpected effect of a partial multiple bond between phosphorus and fluorine in 7 J P -H and 3 J P -H .

Cholinesterases are targets for organophosphorus compounds which are used as pesticides, insecticides, chemical warfare agents and drugs for the treatment of disease such as glaucoma or parasitic infections. Most organophosphorus compounds impart their toxic action via inhibition of cholinesterases by reacting at an essential serine hydroxyl group. The inhibition process depends on the leaving group, stereochemistry and reactivity of the organophosphorus compound. In this study, the inhibitory potency of two isoelectronic and isostructural diaza- and dioxophospholes A (CH3C6H3 O2P(O)Cl) and B (CH3C6H3(NH)2P(O)Cl) against human acetylcholinesterase (hAChE) was examined by spectrophotometric measurements based on Ellman's method. Results indicated that compounds A and B were irreversible inhibitors with IC50 values of 0.48 and 1.54mM, respectively and inactivation constants (k(i)) of 0.0363 and 0.0207min(-1), respectively. The differences in the inhibitory potency of two phosphole compounds is discussed with respect to their structures. In addition, the synthesis and characterization of compound A is discussed.