Qhov Tseem Ceeb Qhov txawv - Syn vs Anti Ntxiv
Nyob rau hauv cov organic chemistry, cov tshuaj tiv thaiv ntxiv yog tus cwj pwm los ntawm ob pawg uas sib cog lus rau ob daim ntawv cog lus. Thaum lub sij hawm no tus yam ntxwv ntxiv cov tshuaj tiv thaiv ntawm alkenes, p daim ntawv cog lus ntawm ob daim ntawv cog lus yog tawg thiab tshiab σ bonds raug tsim. Nws yog vim tias p daim ntawv cog lus ntawm C=C daim ntawv cog lus muaj zog dua thiab tsis ruaj khov dua li C-C σ daim ntawv cog lus. Ntxiv mus, p daim ntawv cog lus ntawm alkenes ua rau lawv cov electron nplua nuj, raws li p daim ntawv cog lus lub electron ceev yog concentrated saum toj no thiab hauv qab lub dav hlau ntawm lub molecule. Yog li ntawd, p daim ntawv cog lus yog qhov yooj yim rau σ electrophiles dua li daim ntawv cog lus. Lub stereochemistry yog qhov tseem ceeb hauv kev txiav txim siab cov txheej txheem ntawm cov tshuaj tiv thaiv ntxiv. Lub stereochemistry ntawm cov tshuaj tiv thaiv ntxiv yog nyob ntawm ob yam. Thawj qhov yog qhov sib koom ua ke ntawm electrophile thiab nucleophile mus rau ob daim ntawv cog lus carbons (txawm nws yog los ntawm tib sab ntawm ob daim ntawv cog lus lossis los ntawm sab nraud). Qhov thib ob yog qhov geometrical orientation ntawm electrophile thiab nucleophile rau ib leeg thiab lwm yam ntawm cov organic molecule. Raws li cov yam ntxwv no, muaj ob qhov ua tau stereochemistry rau qhov sib ntxiv, syn thiab anti. Qhov sib txawv tseem ceeb ntawm kev sib ntxiv thiab kev sib ntxiv yog qhov sib ntxiv, ob qho tib si electrophile thiab nucleophile ntxiv los ntawm tib sab ntawm lub dav hlau ntawm ob-bonded carbon atoms, whereas nyob rau hauv anti-ntxiv, nucleophile thiab electrophile ntxiv los ntawm opposite sab ntawm lub dav hlau no.. Cov ntsiab lus ntxiv hais txog kev sib txuas thiab kev tiv thaiv ntxiv tau tham hauv qab no.
Syn Ntxiv yog dab tsi?
Syn ntxiv yog qhov ua tau stereochemistry ntawm qhov sib ntxiv qhov twg ob qho tib si electrophile thiab nucleophile daim ntawv cog lus rau tib sab ntawm lub dav hlau ntawm ob-bonded carbon atoms ntawm alkene. Kev sib ntxiv feem ntau tshwm sim thaum alkenes muaj qhov hloov pauv aryl.
Daim duab 01: Syn and Anti Addition
Ntxiv mus, nws tshwm sim hauv hydroboration. Thaum lub sij hawm hydrohalogenation thiab hydration, ob qho tib si syn thiab anti ntxiv tuaj yeem tshwm sim. Thaum lub sij hawm hydroboration, thawj kauj ruam yog tsim ib qho nruab nrab alkylborane los ntawm qhov sib ntxiv ntawm H thiab BH 2rau p daim ntawv cog lus ntawm alkene. Tom qab ntawd hauv kauj ruam thib ob, H-BH 2 thiab p daim ntawv cog lus tau tawg los ua cov ntawv cog lus tshiab. Qhov kev hloov pauv ntawm cov tshuaj tiv thaiv no yog plaub-qhov nruab nrab vim tias plaub lub atoms koom nrog los tsim qhov nruab nrab.
Anti Addition yog dab tsi?
Anti ntxiv yog ib qho ua tau stereochemistry ntawm qhov sib ntxiv qhov twg electrophile thiab nucleophile daim ntawv cog lus mus rau sab nraud ntawm lub dav hlau ntawm ob-bonded carbon atoms ntawm alkene. Kev tiv thaiv ntxiv tshwm sim hauv halogenation thiab halohydrin tsim. Halogenation yog qhov sib ntxiv ntawm X2 (qhov twg X=Br lossis Cl). Halogenation ntawm alkenes muaj ob kauj ruam.
Hauv thawj kauj ruam, qhov sib ntxiv ntawm electrophile (X+) rau p daim ntawv cog lus tau tshwm sim. Thaum lub sij hawm cov kauj ruam no, ib lub nplhaib peb-tus tswv cuab nrog zoo them halogen atom hu ua bridged halonium ion yog tsim. Thawj kauj ruam yog qhov ntsuas tus nqi. Tom qab ntawd hauv kauj ruam thib ob, nucleophilic nres ntawm X– tshwm sim. Thaum lub sij hawm no, X– tawm tsam lub nplhaib ntawm halonium ion qhib nws thiab tom qab ntawd tsim C-X daim ntawv cog lus tshiab.
Qhov txawv ntawm Syn thiab Anti Addition yog dab tsi?
Syn Ntxiv vs Anti Ntxiv |
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| Syn Ntxiv yog qhov ua tau zoo ntawm qhov sib ntxiv qhov twg ob qho tib si electrophile thiab nucleophile daim ntawv cog lus rau tib sab ntawm lub dav hlau ntawm ob-bonded carbon atoms ntawm alkene. | Anti-Addition yog ib qho ua tau stereochemistry ntawm qhov sib ntxiv qhov twg electrophile thiab nucleophile daim ntawv cog lus rau sab nraud ntawm lub dav hlau ntawm ob daim ntawv cog lus carbon atoms ntawm alkene |
| Ntxiv Reactions | |
| YHydroboration, Hydrohalogenation thiab Hydration | Y Halogenation, Halohydrin tsim, Hydrohalogenation thiab Hydration |
Summary – Syn vs Anti Addition
Alkenes yog tus cwj pwm los ntawm cov tshuaj tiv thaiv ntxiv, uas tau muab faib ua ob hom raws li stereochemistry; sib ntxiv thiab anti ntxiv. Thaum sib ntxiv, p daim ntawv cog lus ntawm C=C tawg los tsim σ daim ntawv cog lus tshiab. Tsis tas li ntawd, ob qho tib si nucleophile thiab electrophile bonds rau tib sab ntawm lub dav hlau ntawm p daim ntawv cog lus ntawm C=C daim ntawv cog lus ntawm alkene, whereas nyob rau hauv anti ntxiv, nucleophile thiab electrophile ntxiv rau opposite sab ntawm lub dav hlau ntawm p daim ntawv cog lus. Qhov no yog qhov txawv ntawm syn thiab anti ntxiv.
Download the PDF Version of Syn vs Anti Addition
Koj tuaj yeem rub tawm PDF version ntawm kab lus no thiab siv nws rau offline hom phiaj raws li daim ntawv ceeb toom. Thov download PDF version ntawm no Qhov txawv Ntawm Syn thiab Anti Ntxiv
