Qhov Tseem Ceeb Qhov txawv - Markovnikov vs Anti-Markovnikov Txoj Cai
Nyob rau thaum ntxov 1870s, ib tug kws tshuaj Lavxias teb sab hu ua Vladimir Markonikov muab ib txoj cai raws li ib tug series ntawm empirical soj ntsuam. Txoj cai tau luam tawm raws li Markovnikov txoj cai. Txoj cai Markovnikov pab kwv yees cov txiaj ntsig ntawm alkane, thaum cov khoom sib xyaw uas muaj cov qauv ntawm HX (HCl, HBr lossis HF) lossis H 2 O yog ntxiv rau asymmetric alkene (xws li. raws li propane). Nws muaj peev xwm thim rov qab cov khoom me thiab cov khoom loj thaum cov kev hloov pauv hloov, thiab cov txheej txheem no hu ua Anti-Markovnikov ntxiv. Qhov sib txawv tseem ceeb ntawm txoj cai Markovnikov thiab txoj cai tiv thaiv Markovnikov tau piav qhia hauv qab no.
Txoj cai Markovnikov yog dab tsi?
Lub ntsiab lus ntawm txoj cai Markovnikov yog, thaum sib ntxiv ntawm protic acid nrog cov qauv ntawm HX (qhov twg X=halogen) los yog H 2O (siv li H-OH) rau ib qho alkene, hydrogen txuas rau ob chav sib txuas nrog cov pa roj carbon ntau dua, thaum lub halogen (X) txuas rau lwm cov pa roj carbon. Yog li, txoj cai no feem ntau txhais tau tias 'cov nplua nuj tau nplua nuj'. Txoj cai tuaj yeem piav qhia siv cov tshuaj tiv thaiv ntawm propene nrog hydrobromic acid (HBr) raws li hauv qab no.
Daim duab 01: Markovnikov Txoj Cai yog qhia los ntawm cov tshuaj tiv thaiv ntawm Propene nrog Hydrobromic Acid
Txoj cai tib yam yog siv thaum alkene reacts nrog dej los tsim cawv. Cov pab pawg hydroxyl (-OH) ntxiv rau cov pa roj carbon ob npaug nrog ntau dua ntawm C-C daim ntawv cog lus, thaum cov hydrogen atom (H) ntxiv rau lwm cov pa roj carbon monoxide uas muaj C-H ntau dua. Yog li ntawd, raws li Markovnikov txoj cai, thaum ib qho HX ntxiv rau alkene, cov khoom loj muaj H atom nyob rau hauv txoj hauj lwm tsawg dua thaum lub X nyob rau hauv txoj hauj lwm ntau hloov. Yog li ntawd, cov khoom no ruaj khov. Txawm li cas los xij, nws tseem muaj peev xwm tsim cov khoom lag luam tsis tshua muaj zog, lossis peb hu nws ua cov khoom me, uas H atom daim ntawv cog lus rau ntau qhov hloov pauv ntawm C=C daim ntawv cog lus, thaum X daim ntawv cog lus rau txoj hauj lwm tsawg dua.
Daim duab 02: Hydrogen Bromide ntxiv rau Alkene
Lub tshuab ntawm qhov sib ntxiv ntawm HX rau ib qho alkene tuaj yeem piav qhia hauv ob kauj ruam (Saib daim duab 02). Ua ntej, qhov sib ntxiv ntawm ib qho proton (H+) yog tshwm sim raws li C=C ob daim ntawv cog lus ntawm alkene reacts nrog H+ ntawm HX (Nyob rau hauv cov ntaub ntawv no nws yog HBr) los tsim ib tug carbonation intermediate. Tom qab ntawd cov tshuaj tiv thaiv ntawm ib qho electrophile thiab nucleophile tau tshwm sim raws li kauj ruam thib ob los tsim ib daim ntawv cog lus tshiab. Nyob rau hauv peb rooj plaub, Br– reacts nrog carbonation intermediate uas yog zoo nyob rau hauv tus nqi los tsim cov khoom kawg.
Txoj cai Anti-Markovnikov yog dab tsi?
Anti- Markovnikov txoj cai piav qhia qhov tsis sib xws ntawm thawj nqe lus ntawm Markovnikov txoj cai. Thaum HBr ntxiv rau alkene nyob rau hauv lub xub ntiag ntawm peroxide, H atom bonds rau ob-bonded carbon uas muaj tsawg C-H bonds, thaum Br bonds rau lwm cov pa roj carbon uas muaj ntau C-H bonds. Cov nyhuv no tseem hu ua Kharash effect lossis peroxide effect. Cov tshuaj tiv thaiv Markovnikov ntxiv kuj tshwm sim thaum cov reactants raug ultraviolet lub teeb. Qhov no yog qhov tseeb ntawm Markovnikov txoj cai. Txawm li cas los xij, txoj cai tiv thaiv Markovnikov tsis yog tus txheej txheem thim rov qab ntawm Markovnikov ntxiv vim tias cov txheej txheem ntawm ob qhov kev cuam tshuam no txawv kiag li.
Markovnikov cov tshuaj tiv thaiv yog ib qho ionic mechanism, thaum anti-Markovnikov cov tshuaj tiv thaiv yog ib tug dawb-radical mechanism. Lub tshuab yuav siv qhov chaw raws li cov tshuaj tiv thaiv kab mob thiab muaj peb kauj ruam. Thawj kauj ruam yog cov kauj ruam pib, qhov twg photochemical dissociation ntawm HBr los yog peroxide yog coj qhov chaw los ua Br thiab H dawb radicals. Tom qab ntawd hauv kauj ruam thib ob, Br dawb radical tawm tsam cov alkene molecule los tsim ob qho bromoalkyl dawb radicals. 2 ° dawb radical yog ruaj khov thiab tsim feem ntau.
Daim duab 3: Anti- Markovnikov Ntxiv Piv txwv
Thaum lub sijhawm kawg, qhov ruaj khov bromoalkyl dawb radical reacts nrog HBr tsim los tiv thaiv Markovnikov cov khoom ntxiv rau lwm cov bromine dawb radical, uas txuas ntxiv cov tshuaj tiv thaiv kab mob. Tsis zoo li HBr, HCl thiab HI tsis ua rau cov khoom siv los tiv thaiv Markovnikov vim lawv tsis muaj cov tshuaj tiv thaiv dawb radical ntxiv. Nws yog vim H-Cl daim ntawv cog lus muaj zog dua H-Br daim ntawv cog lus. Txawm hais tias H-I daim ntawv cog lus qis dua, kev tsim ntawm I 2 yog qhov nyiam dua li C-I daim ntawv cog lus tsis ruaj khov.
Qhov txawv ntawm Markovnikov thiab Anti Markovnikov Txoj Cai yog dab tsi?
Markovnikov vs Anti Markovnikov Txoj Cai |
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| Markovnikov Txoj Cai piav qhia thaum sib ntxiv ntawm protic acid nrog cov qauv ntawm HX (qhov twg X=halogen) lossis H 2O (siv li H-OH) rau ib qho alkene, hydrogen txuas mus rau ob daim ntawv sib txuas nrog ntau dua ntawm hydrogen atoms, thaum lub halogen (X) txuas rau lwm cov pa roj carbon. | Anti-Markovnikov Txoj Cai piav qhia thaum HBr ntxiv rau alkene nyob rau hauv lub xub ntiag ntawm peroxide, H atom bonds rau ob-bonded carbon uas muaj tsawg C-H bonds, thaum Br bonds rau lwm cov pa roj carbon uas muaj ntau C-H bonds |
| Mechanism | |
| Ionic mechanism | Free radical mechanism |
| Reactants | |
| HCl, HBr, HI or H2O | Tsuas HBr (tsis yog HCl lossis HI tau txais cov tshuaj tiv thaiv ntxiv no) |
| Nrab/Catalyst | |
| Tsis xav tau nruab nrab | Peroxide lossis ultraviolet yuav tsum muaj |
Summary – Markovnikov vs Anti-Markovnikov Txoj Cai
Markovnikov thiab anti-Markovnikov yog ob hom kev sib ntxiv tshwm sim ntawm HX (HBr, HBr, HI thiab H 2 O) thiab alkenes. Markovnikov cov tshuaj tiv thaiv tshwm sim thaum qhov sib ntxiv ntawm HX mus rau ib qho alkene, qhov twg H bonds rau tsawg dua cov pa roj carbon atom ntawm ob daim ntawv cog lus, thaum X bonds rau lwm ob ob bonded carbon atom los ntawm ib tug ionic mechanism. Cov tshuaj tiv thaiv anti-markovnikov tshwm sim thaum HBr (tsis yog HCl, HI lossis H2O) ntxiv rau alkene, qhov twg Br bonds tsawg dua cov pa roj carbon monoxide, thaum H bonds rau lwm cov pa roj carbon atom, los ntawm cov khoom siv dawb radical. Qhov no yog qhov txawv ntawm Markovnikov thiab Anti-Markovnikov Txoj Cai.
Download PDF ntawm Markovnikov vs Anti-Markovnikov Txoj Cai
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 rub tawm PDF version ntawm no Qhov txawv Ntawm Markovnikov thiab Anti Markovnikov Txoj Cai
