Qhov sib txawv tseem ceeb ntawm Fischer thiab Schrock carbene yog Fischer carbene muaj cov hlau tsis muaj zog rov qab thaum Schrock carbene muaj cov hlau txuas rov qab.
A carbene compound yog cov tshuaj lom neeg uas muaj cov pa roj carbon nruab nrab uas muaj qhov sib npaug ntawm ob thiab ob qho tsis sib koom valence electrons. Cov mis loj ntawm carbene yog R=R ' lossis R=C qhov twg R sawv cev rau cov khoom siv los yog hydrogen atoms. Muaj ob hom carbene xws li Fischer carbene thiab Schrock carbene.
Fischer Carbene yog dab tsi?
Fischer carbene yog hom hlau-carbon compound uas muaj qhov tsis muaj zog rov qab sib txuas hlau chaw. Qhov chaw hlau no feem ntau yog qhov chaw qis oxidation xeev hlau. Kev hloov pauv nruab nrab thiab lig ntawm cov kev hloov pauv xws li hlau, molybdenum thiab cob alt tuaj yeem pom hauv cov carbene molecules. Tsis tas li ntawd, cov tshuaj no muaj pi-donating R pawg. Hauv lwm lo lus, Fischer carbenes muaj pi-acceptor hlau ligands. Cov pab pawg R feem ntau suav nrog alkoxy thiab alkylated amino pawg.
Daim duab 01: Tshuaj Bonding hauv Carbene Compounds
Fischer carbene molecules muaj feem xyuam rau ketones hauv cov khoom siv tshuaj vim tias cov pa roj carbon atom hauv carbene yog electrophilic zoo ib yam li carbonyl carbon ntawm ketone molecule. Ntxiv mus, zoo ib yam li cov ketones, Fischer carbenes tuaj yeem ua rau muaj kev cuam tshuam zoo li aldol. Tsis tas li ntawd, cov pa roj carbon atom uas yog alpha rau carbene-carbon yog acidic thiab tuaj yeem deprotonated los ntawm cov hauv paus xws li n-butyllithium.
Schrock Carbene yog dab tsi?
Schrock carbene yog hom hlau-carbon compound uas muaj lub zog rov qab sib txuas hlau qhov chaw. Cov carbene tebchaw no tsis muaj pi- txais cov hlau ligands. Txawm li cas los xij, muaj pi-donating ligands. Ntawm qhov chaw carbene-carbon, qhov sib xyaw no yog nucleophilic. Feem ntau, peb tuaj yeem soj ntsuam lub siab oxidation xeev hlau chaw hauv cov tebchaw no. Feem ntau, cov hlau hloov thaum ntxov xws li titanium thiab tantalium tuaj yeem pom nyob rau hauv cov tebchaw no.
Qhov txawv ntawm Fischer thiab Schrock Carbene yog dab tsi?
A carbene compound yog cov tshuaj lom neeg uas muaj cov pa roj carbon nruab nrab uas muaj qhov sib npaug ntawm ob thiab ob qho tsis sib koom valence electrons. Muaj ob hom carbene xws li Fischer carbene thiab Schrock carbene. Qhov sib txawv tseem ceeb ntawm Fischer thiab Schrock carbene yog tias Fischer carbene muaj cov hlau tsis zoo rov qab thaum Schrock carbene muaj cov hlau nplaum zoo heev.
Tsis tas li ntawd, feem ntau, Fisher carbene tebchaw muaj qis oxidation xeev hlau chaw zov me nyuam thaum Schrock carbene cov chaw muaj oxidation xeev hlau chaw. Yog li ntawd, Fischer carbenes feem ntau muaj cov hlau hloov nruab nrab thiab lig xws li isorn, molybdenum, thiab cob alt thaum Schrock carbenes feem ntau muaj cov hlau hloov thaum ntxov xws li titanium thiab tantalum. Yog li, qhov no yog lwm qhov sib txawv ntawm Fischer thiab Schrock carbene.
Ntxiv mus, Fischer carbene muaj pi-acceptor hlau ligands thaum Schrock carbene compounds muaj pi-donor hlau ligands. Hauv lwm lo lus, Fischer carbene muaj pi-donating R pawg. Li no, qhov no kuj yog qhov sib txawv tseem ceeb ntawm Fischer thiab Schrock carbene. Tsis tas li ntawd, Fischer carbene tebchaw tuaj yeem ua raws li electrophiles vim tias lawv yog electrophilic ntawm carbene-carbon center. Txawm li cas los xij, Schrock carbenes yog nucleophilic compounds. Dhau li ntawd, R pawg ntawm Fischer carbene suav nrog alkoxy thiab alkylated amino pawg thaum R pawg ntawm Schrock carbene suav nrog hydrogen thiab alkyl substituents.
Hauv qab infographic qhia txog qhov sib txawv ntawm Fischer thiab Schrock carbene.
Summary – Fischer vs Schrock Carbene
Muaj ob hom carbene xws li Fischer carbene thiab Schrock carbene. Fischer carbene yog ib hom hlau-carbon compound uas muaj qhov tsis muaj zog rov qab sib txuas hlau qhov chaw thaum Schrock carbene yog hom hlau-carbon compound uas muaj zog rov qab sib txuas hlau chaw. Yog li ntawd, qhov sib txawv tseem ceeb ntawm Fischer thiab Schrock carbene yog tias Fischer carbene muaj cov hlau tsis zoo rov qab thaum Schrock carbene muaj cov hlau nplaum zoo heev.
