INFLUENCE OF SIGMA VALUE OF SUBSTIT
UENT ON ACTIVITY OF OP INSECTICIDES

COMPOUND  SIGMAX  I50(NM)LD50(µG/G)
4-NO2     1.27      26.0     1.22.~
3-NME3+   0.88      30.0  >500.05.~
4-CN      1.00     130.0     3.54.~
4-SO2CH3  1.05     250.0     2.03.~
4-SOCH3   0.57    3100.0     1.56.~
4-CL      0.23   30000.0   150.07.~
4-SCH3    0.00   33000.0     2.50.~
3-OCH3    0.12  130000.0  >500.08.~

valueindicatesno 4shouldnotphosphor
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thedemeton likeanalogsareoxidizedfr
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tionrateconstantschangebyanorderofm
however whengivendirectaccesstothet
eester orthemorereadilytheinsectici
ngsterichinderances  thusthefirstan
athaveafixedchargesuchasthequaterna
argetsite ache thequarternarynitrog
hibitionvalues theseresultsarerelat
dephosphorylatestheenzyme discounti
theanionicsiteratherwellimprovingth
tyandinhibitionunits inaddition the
edtothefitattheanionicsiteaswell as
elistabovearegivenwiththesametoxici
sbothoutstandinginhibitionandhighto
undingtheinsectcentralnervoussystem
engroupincompoundno 4apparentlyfits
on thelistabovecontainsapeculiarres
forcomparison allofthecompoundsinth
itor however compoundno 4 isnon tox
rynitrogengroupshownincompoundsno 4
ananionicchargesmoiety andtheinhibi
alog paraoxon compoundno 1 itselfha
lysisrateofthecorrespondingphosphat
ylatetheenzymenearlyaswellasparasox
ultinthatcompounds2 5and8allhavesim
fonetheyareincreasinglyattractiveto
gerthesigmavalue thegreaterthehydro
xicitytohousefly thesecondbestinhib
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omthesulfurtothesulfoxideandthensul
isrelativelyimpervioustocompoundsth
analogsarelistedbysigmavalue thelar
agnitudeateachofoxidationsteps  PbN