Pyrethroid tshuaj tua kab muaj cov yam ntxwv muaj zog chiral thiab feem ntau muaj ntau yam chiral enantiomers. Thaum cov enantiomers muaj cov khoom zoo tib yam physicochemical, lawv pom cov kab mob sib txawv, biotoxicity, thiab ib puag ncig residue qib. Piv txwv li cypermethrin,Beta-Cypermethrin, Alpha{0}}Cypermethrin, thiabLambda-Cyhalothrin.
Cypermethrin:
Cypermethrin, feem ntau siv tshuaj tua kab pyrethroid, muaj peb lub chaw chiral hauv nws cov qauv molecular thiab yim enantiomers. Cov kev ua lom lom thiab tshuaj lom uas nthuav tawm los ntawm cov enantiomers sib txawv sib txawv.
Cypermethrin muaj yim optical isomers, tsim plaub pawg racemic. Cov isomers sib txawv ntawm cypermethrin pom qhov sib txawv tseem ceeb hauv lawv cov tshuaj tua kab thiab cov nqi photolysis. Lawv cov tshuaj tua kab, los ntawm qhov muaj zog tshaj plaws mus rau qhov tsis muaj zog, yog raws li hauv qab no: cis-, trans-, thiab cis-trans-cypermethrin.
Ntawm yim isomers ntawm cypermethrin, ob ntawm txhua ntawm plaub trans- thiab plaub cis-isomers muaj zog heev.
Txawm li cas los xij, kev siv ib qho isomer uas muaj zog heev ntawm cypermethrin ua cov tshuaj tua kab tsis tsuas yog txhim kho nws cov tshuaj tua kab tab sis kuj txo cov tshuaj lom rau cov kab mob uas tsis yog -cov kab mob thiab kev cuam tshuam ib puag ncig. Yog li ntawd, beta-cypermethrin thiab alpha-cypermethrin tau tsim:
Alpha{0}}cypermethrin
Alpha-cypermethrin tseem hu ua -cypermethrin. Nws cais ob qhov tsis muaj txiaj ntsig lossis tsis muaj txiaj ntsig isomers los ntawm kev sib xyaw ntawm plaub cis isomers, uas ua rau muaj kev sib xyaw uas tsuas muaj ob lub cis isomers uas muaj txiaj ntsig zoo hauv 1: 1 piv.
Alpha-cypermethrin muaj ob zaug cov tshuaj tua kab ntawm cypermethrin.
Beta{0}}cypermethrin
Beta-cypermethrin, tseem hu ua cis zoo heev -trans cypermethrin, yog ib qho sib xyaw ntawm cov isomers tsis zoo ntawm yim-isomer technical ntawm industrial cypermethrin. Qhov no yog ua tiav los ntawm catalytically isomerizing cov isomers ineffective ntawm cov txheej txheem ntawm cypermethrin rau cov isomers zoo heev. Qhov no ua rau muaj kev sib xyaw ua ke ntawm cov cis thiab trans isomers zoo heev, piv txwv li, plaub isomers hauv cis: trans piv ntawm kwv yees li 40: 60 lossis 2: 3.
Beta-cypermethrin muaj tib yam tshuaj tua kab zoo li cypermethrin, tab sis nws cov tshuaj tua kab muaj peev xwm kwv yees li ob zaug siab dua.
Beta-cypermethrin tsis tshua muaj tshuaj lom rau tib neeg thiab tsiaj txhu, thiab nws cov tshuaj lom rau cov kab tsuag huv si sib npaug los yog ntau dua li ntawm alpha-cypermethrin, yog li muab qee qhov zoo hauv kev tswj xyuas kab tsuag.
Cov ntsiab lus:
Since the cis-isomer is generally more bioactive than the trans-isomer, the order of insecticidal activity among the three cypermethrins should be: alpha-cypermethrin ≥ beta-cypermethrin >>tshuaj cypermethrin.
Txawm li cas los xij, beta-cypermethrin nthuav tawm cov tshuaj tua kab mob zoo dua qub piv rau lwm ob.
