Qhov sib txawv tseem ceeb ntawm Wittig cov tshuaj tiv thaiv thiab kev hloov kho Wittig yog tias Wittig cov tshuaj tiv thaiv tsim cov tshuaj alkene ua cov khoom kawg thaum Wittig rearrangement tsim cov cawv lossis cov ketone sib raug raws li cov khoom kawg.
Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement yog qhov tseem ceeb heev hauv cov organic chemistry rau cov txheej txheem hluavtaws. Ib qho kev kho dua tshiab tshwm sim tom qab muaj kev cuam tshuam los tsim cov khoom ruaj khov kawg kawg.
Wittig Reaction yog dab tsi?
Hauv cov tshuaj lom neeg, Wittig cov tshuaj tiv thaiv yog ib hom kev sib txuas cov tshuaj tiv thaiv uas aldehydes los yog ketones hnov mob nrog phosphonium ylides, tsim ib qho alkene. Peb tuaj yeem hu cov tshuaj tiv thaiv no li Wittig olefination cov tshuaj tiv thaiv vim nws tsim cov olefin ua cov khoom kawg. Ntxiv mus, cov tshuaj tiv thaiv no tau muab npe tom qab tus kws tshawb fawb Georg Wittig. Qhov loj reagent hauv cov tshuaj tiv thaiv no yog phosphonium ylide - peb tuaj yeem hu nws ua Wittig reagent vim tias cov tshuaj reactant no tshwj xeeb rau cov tshuaj tiv thaiv Wittig. Sib nrug los ntawm alkene, qhov tshuaj tiv thaiv no muab lwm yam khoom, triphenylphosphine oxide.
Daim duab 01: Wittig Reaction hauv Kev Sib Tw Dav Hlau
Wittig cov tshuaj tiv thaiv yog qhov tseem ceeb hauv kev tsim cov alkenes hauv cov txheej txheem organic synthesis. Peb tuaj yeem faib cov tshuaj tiv thaiv no ua kev sib txuas lus vim nws suav nrog kev sib txuas ntawm aldehydes thiab ketones rau triphenylphosphonium ylides. Qhov xwm ntawm cov khoom alkene nyob ntawm qhov ruaj khov ntawm ylide.i.e. unstabilized ylides muab Z-alkenes, thiab stabilized ylides muab E-alkene. Txawm li cas los xij, kev tsim ntawm E-alkene yog qhov kev xaiv heev hauv cov tshuaj tiv thaiv no.
Wittig Rearrangement yog dab tsi?
Wittig rearrangement yog ib hom kev hloov pauv ntawm ib daim ntawv mus rau lwm daim ntawv nyob ntawm kev ruaj ntseg. Muaj ob lub ntsiab ntawm Wittig rearrangement: 1, 2-Wittig rearrangement thiab 2, 3-Wittig rearrangement.
1, 2-Wittig rearrangement yog cov tshuaj tiv thaiv nyob rau hauv cov organic chemistry qhov twg ether undergoes rearrangement nrog ib tug alkylithium compound. Cov qauv tshuaj siv dav dav rau cov tshuaj tiv thaiv no yog raws li hauv qab no:
Daim duab 02: Cov Qauv Tshuaj General rau 1, 2-Wittig rearrangement
Cov tshuaj tiv thaiv no suav nrog kev tsim cov alkoxy lithium ntsev raws li qhov nruab nrab thiab cov khoom kawg ntawm cov tshuaj tiv thaiv yog cawv. Txawm li cas los xij, yog tias cov ether muaj cov pab pawg zoo xws li cyanide pawg, (raws li qhia hauv daim duab saum toj no) uas muaj peev xwm tshem tawm electrons. Cov pab pawg no raug tshem tawm thaum lub sijhawm rov kho dua, tsim cov ketone sib raug.
Thaum 2, 3-Wittig rearrangement, kev hloov pauv tshwm sim, hloov pauv ib qho allylic ether rau hauv homoallylic cawv. Qhov kev hloov pauv no tshwm sim los ntawm kev sib tham thiab txheej txheem pericyclic. Yog li ntawd, cov tshuaj tiv thaiv no nthuav tawm qib siab ntawm stereocontrol yog li, peb tuaj yeem siv nws hauv cov txheej txheem hluavtaws thaum ntxov hauv stereochemistry. Feem ntau, qhov kev hloov kho Wittig no yuav tsum muaj ib puag ncig zoo. Ntxiv mus, nws yog cov txheej txheem sib tw rau 1, 2-Wittig rearrangement.
Qhov txawv ntawm Wittig Reaction thiab Wittig Rearrangement yog dab tsi?
Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement yog ib qho tseem ceeb hauv cov organic chemistry. Qhov sib txawv tseem ceeb ntawm Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement yog tias Wittig cov tshuaj tiv thaiv tsim cov alkene ua cov khoom kawg thaum Wittig rearrangement tsim cov cawv los yog cov ketone sib raug raws li cov khoom kawg.
Hauv qab infographic tabulates qhov sib txawv ntawm Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement.
Summary – Wittig Reaction vs Wittig Rearrangement
Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement yog ib qho tseem ceeb hauv cov organic chemistry. Qhov sib txawv tseem ceeb ntawm Wittig cov tshuaj tiv thaiv thiab Wittig rearrangement yog tias Wittig cov tshuaj tiv thaiv tsim cov alkene ua cov khoom kawg thaum Wittig rearrangement tsim cov cawv los yog cov ketone sib raug raws li cov khoom kawg.
