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Quantitative structure‐activity relationships were derived for acetyl‐ and butyrylcholinesterase inhibition by various organophosphorus esters. Bimolecular inhibition rate constants correlate well with hydrophobic substituent constants, and with the presence or absence of cationic groups on the inhibitor, but not with steric substituent constants. CNDO/2 calculations were performed on a separate set of organophosphorus esters, RR′P(O)X, where R and R′ are alkyl and/or alkoxy groups and X is fluorine, chlorine or a phenoxy group. For each subset with the same X, the CNDO‐derived net atomic charge at the central phosphorus atom in the ester correlates well with the alkaline hydrolysis rate constant. For the whole set of esters with different X, two equations were derived that relate either charge and leaving group steric bulk, or orbital energy and bond order to the hydrolysis rate constant.

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. 55,3086 (1977). The kinetics of the reaction of mercuric acetate with alkenes in methanol can be measured directly by observing the ultraviolet absorbance of the solution at 265 nrn. For more reactive alkenes stopped flow techniques are required, but for less reactive substrates conventional spectrophotorneters are adequate. The measured rates are in satisfactory agreement with values obtained by other methods. The rates of several cyclopropylalkenes were measured in this way, and relative reactivities of some of the same substrates were obtained by the competition method. Rates obtained by both methods are in qualitative agreement, and show very high reactivity for the cyclopropylalkenes. These rates are analyzed by comparison with model reactions involving open ions (acid-catalyzed hydration) and bridged ions (sulfenyl halide addition). The comparisons suggest that the oxyrnercuration of alkenes not substituted with strongly resonance electron-donating substituents, for example ethylene, proceeds through bridged rate-determining transition states that put very little positive charge on carbon, but that when strongly resonance electron-donating substituents such as cyclopropyls are present, the rate-determining transition state resembles an open carboniurn ion.Chern. 55,3086 (1977).On peut rnesure la cinetique de la reaction de I'acetate mercurique avec les alcenes dans le methanol d'une manitre directe en observant l'absorption dans I'ultraviolet d'une solution a 265 nrn. Pour les alcenes reactifs, on doit faire appel aux techniques de flux stoppes mais pour des substrats moins reactifs, des rnethodes spectrophotornCtriques conventionnelles sont adequates. Les vitesses mesurtes sont en bon accord avec les valeurs obtenues par d'autres rnethodes. De cette rnaniere on a rnesure les vitesses de reaction de plusieurs cyclopropylalkenes et des reactivitks relatives de quelques uns des mCrnes substrats ont pu Ctre obtenues par des methodes cornpktitives. Les vitesses obtenues par les deux methodes sont en bon accord qualitatif et indiquent une tres grande reactivite pour les cyclopropylalkenes. On a analyse ces vitesses par cornparaison avec des reactions rnodkles impliquant des ions ouverts (I'hydratation acido-catalyske) et des ions pontes (addition de l'halogenure de sulfenyle). Ces comparaisons suggerent que l'oxyrnercuration des alcenes non-substitues par des substituants agissant comrne electro-donneurs puissants par resonance, par exernple l'kthylene, procede par des Ctats de transition dkterrninant la vitesse de la reaction qui sont pontes et qui induisent trts peu de charge positive au niveau du carbone; toutefois lorsque des substituants agissant forternent cornrne des Clectro-donneurs a cause de la resonance tel que le cyclopropyle, sont presents, I'Ctat de transition determinant la vitesse ressernble a un ion en forme ouverte.[Traduit par le journal]The oxymercuration reaction has been exten- mercury species is unknown in most cases. For It has been established that the rate of oxy-reactions in 0.01 M ...