Qhov sib txawv tseem ceeb ntawm Wittig thiab Wittig Horner cov tshuaj tiv thaiv yog tias Wittig cov tshuaj tiv thaiv siv phosphonium ylides, qhov Wittig Horner cov tshuaj tiv thaiv siv phosphonate-stabilized carbanions.
Wittig cov tshuaj tiv thaiv thiab Wittig Horner cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv tseem ceeb hauv cov tshuaj lom neeg, uas tsim cov alkenes los ntawm aldehydes lossis ketones. Cov tshuaj tiv thaiv no txawv ntawm ib leeg nyob ntawm cov reactants uas muaj nyob rau hauv cov tshuaj tiv thaiv, nrog rau aldehyde los yog ketone.
Wittig Reaction yog dab tsi?
Wittig cov tshuaj tiv thaiv yog ib hom kev sib txuas cov tshuaj tiv thaiv uas aldehydes lossis ketones hnov mob nrog phosphonium ylides los muab cov alkene. Tsis tas li ntawd, cov tshuaj tiv thaiv no tseem muaj npe hu ua Wittig olefination cov tshuaj tiv thaiv vim nws tsim cov olefin ua cov khoom kawg. Tsis tas li ntawd, cov tshuaj tiv thaiv no tau raug hu ua tus kws tshawb fawb Georg Wittig. Cov phosphonium ylide yog lub npe hu ua Wittig reagent vim hais tias cov reactant no tshwj xeeb rau cov tshuaj tiv thaiv Wittig. Nrog rau cov alkene, cov tshuaj tiv thaiv no muab lwm yam khoom, triphenylphosphine oxide. Cov tshuaj tiv thaiv dav dav yog raws li hauv qab no:
Daim duab 01: Wittig Reaction
Wittig cov tshuaj tiv thaiv tseem ceeb hauv kev tsim cov alkenes hauv cov organic synthesis. Nws yog ib hom kev sib txuas lus vim nws koom 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 Horner Reaction yog dab tsi?
Wittig Horner cov tshuaj tiv thaiv yog ib hom kev sib txuas cov tshuaj tiv thaiv uas aldehydes lossis ketones ob peb nrog phosphonate-stabilized carbanions muab E-alkenes. Cov tshuaj tiv thaiv no tau muaj npe tom qab peb tus kws tshawb fawb: Leopold Horner, William S. Wadsworth thiab William D. Emmons. Thiab, nws yog qhov hloov pauv ntawm Wittig cov tshuaj tiv thaiv. Tab sis, nyob rau hauv sib piv rau Wittig cov tshuaj tiv thaiv, qhov no Wittig Horner cov tshuaj tiv thaiv siv phosphonate-stabilized carbanions es tsis txhob ntawm phosphonium ylides. Cov carbanions no ntau dua nucleophilic thiab tsawg dua. Tsis tas li ntawd, cov tshuaj tiv thaiv no nyiam tsim cov E-alkene. Cov tshuaj tiv thaiv dav dav yog raws li hauv qab no:
Daim duab 02: Wittig Horner Reaction
Peb tuaj yeem soj ntsuam qhov kev xaiv siab rau E-alkene nyob rau hauv cov xwm txheej xws li nce cov steric bulk ntawm aldehyde, kub tshuaj tiv thaiv, siv cov kuab tshuaj xws li DME, thiab lwm yam. Yog li, qhov no yog lub npe hu ua stereoselectivity ntawm lub Wittig Horner cov tshuaj tiv thaiv.
Qhov txawv ntawm Wittig thiab Wittig Horner Reaction yog dab tsi?
Wittig cov tshuaj tiv thaiv thiab Wittig Horner cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv tseem ceeb uas tsim cov alkenes los ntawm aldehydes lossis ketones. Qhov sib txawv tseem ceeb ntawm Wittig thiab Wittig Horner cov tshuaj tiv thaiv yog tias Wittig cov tshuaj tiv thaiv siv phosphonium ylides, thaum Wittig Horner cov tshuaj tiv thaiv siv phosphonate-stabilized carbanions. Yog li ntawd, cov reactants ntawm Wittig cov tshuaj tiv thaiv yog aldehyde los yog ketone thiab phosphonium ylides, thaum lub reactants ntawm Wittig Horner cov tshuaj tiv thaiv yog aldehydes los yog ketones nrog phosphonate-stabilized carbanions.
Wittig cov tshuaj tiv thaiv tau muab npe tom qab tus kws tshawb fawb Georg Wittig thaum Wittig Horner cov tshuaj tiv thaiv tau muab npe tom qab peb tus kws tshawb fawb: Leopold Horner, William S. Wadsworth thiab William D. Emmons. Ntxiv mus, cov tshuaj tiv thaiv Wittig muab E-alkene lossis Z-alkene nyob ntawm qhov xwm txheej ntawm ylide, piv txwv li cov ylides tsis ruaj khov muab Z-alkene, thiab ylides ruaj khov muab E-alkenes. Txawm li cas los xij, Wittig Horner cov tshuaj tiv thaiv tsuas yog E-alkene. Yog li, qhov no yog lwm qhov sib txawv ntawm Wittig thiab Wittig Horner cov tshuaj tiv thaiv.
Summary – Wittig vs Wittig Horner Reaction
Wittig cov tshuaj tiv thaiv thiab Wittig Horner cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv tseem ceeb hauv cov organic chemistry thiab tsim cov alkenes los ntawm aldehydes lossis ketones. Qhov sib txawv tseem ceeb ntawm Wittig thiab Wittig Horner cov tshuaj tiv thaiv yog tias Wittig cov tshuaj tiv thaiv siv phosphonium ylides, thaum Wittig Horner cov tshuaj tiv thaiv siv phosphonate-stabilized carbanions.
