2024 Tus sau: Elizabeth Oswald | [email protected]. Kawg hloov kho: 2024-01-13 00:07
Kev hloov pauv ntawm acetone oxime hauv cov tshuaj Beckmann koom nrog peb acetic acid molecules thiab ib qho proton (tam sim no raws li oxonium ion). Nyob rau hauv lub xeev hloov pauv ua rau lub iminium ion (σ-complex),pawg methyl tsiv mus rau nitrogen atom hauv kev sib koom ua ke raws li pawg hydroxyl raug tshem tawm.
Qhov kev hloov pauv hloov pauv ntawm Beckmann rov kho dua yog dab tsi?
Kev tsiv teb tsaws ntawm pawg alkyl yog txiav txim siab los ntawm nws txoj kev tsiv teb tsaws chaw xws li electron-nplua nuj. Nws feem ntau ua raws li qhov tseem ceeb ntawm hydride > phenyl > siab dua alkyl > methyl. Cov lus nug tseem ceeb: Kev hloov kho Beckmann kuj tseem cuam tshuam txog kev tsiv teb tsaws alkyl. Txawm li cas los xij, qhov kev tsiv teb tsaws chaw no tsis yog tswj hwm los ntawm kev tsiv teb tsaws chaw.
Lub hauv paus ntsiab lus ntawm Beckmann rearrangement yog dab tsi?
Beckmann rearrangement yog cov tshuaj tiv thaiv organic siv los hloov cov oxime rau ib qho amide nyob rau hauv acidic tej yam kev mob. Cov tshuaj tiv thaiv pib los ntawm protonation ntawm pawg cawv ua ib pawg tawm zoo dua.
Nucleophile twg siv hauv Beckmann rearrangement?
Nucleophile-intercepted Beckmann fragmentation reactions
Mechanistic insights tau coj mus rau qhov kev tshawb pom ntxiv tias oxygen, nitrogen, thiab bromide nucleophiles tuaj yeem ua haujlwm rau qhov kev tawg no los ntawm siv lwm tus txhawb nqa.
Qhov twg yog hloov mus rau amide hauv cov tshuaj tiv thaiv Beckmann?
Mercury chloride(HgCl2) tau txais txiaj ntsig zoo rau Beckmann kev hloov kho ntawm ntau yam ketoximes rau hauv lawv cov amides / lactams sib xws hauv refluxing acetonitrile (Scheme 4, Table 2).
Pom zoo:
Nyob hauv ib pab pawg abelian txhua pawg sub yog?
Txhua pab pawg ntawm pawg neeg abelian yog ib txwm, yog li txhua pab pawg ua rau nce mus rau ib pawg neeg. Subgroups, quotients, thiab ncaj qha sums ntawm abelian pawg yog dua abelian. Cov pab pawg abelian yooj yim kawg nkaus yog cov pab pawg cyclic ntawm kev txiav txim thawj zaug.
Yuav ua li cas txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau pom kev pom?
Txawm li cas los xij, corneal collagen cross-linking - cov txheej txheem qib siab tau pom zoo los ntawm US Food and Drug Administration (FDA) hauv xyoo 2016 - tuaj yeem txhim kho qhov pom kev hauv cov neeg mob txhua hnub nyoog. Corneal collagen cross-linking (CXL) tsis yog kho rau keratoconus, tab sis nws tuaj yeem pab tiv thaiv tus mob kom tsis txhob mob hnyav.
Puas pab pawg pab pawg txhawb nqa pawg?
khoom plig stacks txhua lub sijhawm. Tam sim no, thaum koj qhib MyPlayer nav, nco ntsoov xyuas nrog koj cov xwm txheej. Feem ntau koj tsis tas yuav ua dab tsi kom tau txais koj VC los ntawm lawv, tab sis nws yuav pab tau rau hauv cov ntaub ntawv.
Vim li cas pab pawg tsis ua haujlwm ntawm pab pawg?
Vim li cas pab neeg ua tsis tiav Tsis Muaj Kev Ntseeg. Thaum cov tswv cuab tsis ntseeg ib leeg, lawv zais lawv qhov tsis muaj zog thiab ua yuam kev. … Ntshai ntawm kev tsis sib haum xeeb. Thaum muaj kev ntshai ntawm kev tsis sib haum xeeb ntawm pab pawg, kev sib tham tseem ceeb tsis tshwm sim.
Cov chav sib cais nyob rau hauv pab pawg nyob qhov twg?
Tsim chav sib cais Pib lub rooj sib tham. Nyob hauv lub rooj sib tham tswj, xaiv chav Breakout. Ua raws li hauv qab no: Xaiv cov chav koj xav tau (50 max). Xaiv seb koj puas xav kom Pab Pawg sib npaug muab cov neeg mus rau chav (Tsis Siv Neeg) lossis muab cov neeg koj tus kheej (Manually).
