Qhov Tseem Ceeb Qhov txawv - Esterification vs Transesterification
Esterification thiab transesterification yog ob txheej txheem tseem ceeb ntawm esters. Qhov sib txawv tseem ceeb ntawm esterification thiab transesterification yog qhov ester yog tsim los ntawm esterification whereas ester yog ib qho reactant hauv transesterification.
Ib ester yog cov organic compound uas muaj C, H thiab O atoms. Ib qho ester yog tsim los ntawm kev hloov -Oh pawg ntawm carboxylic acid nrog ib pawg alkoxy. Esters yog polar molecules. Lawv muaj peev xwm tsim tau hydrogen bonds. Qhov no yog vim muaj cov pa oxygen atoms. Esterification txheej txheem tsim esters whereas transesterification hloov esters.
Esterification yog dab tsi?
Esterification yog txheej txheem ntawm kev tsim cov ester los ntawm carboxylic acid thiab cawv. Ib qho ester yog tsim thaum -OH pawg ntawm carboxylic acid hloov los ntawm pawg alkoxy ntawm cawv. Cov txheej txheem esterification yuav tsum muaj ib qho catalyst rau kev nce qib. Cov catalyst yog siv los txo qhov ua kom lub zog thaiv ntawm cov txheej txheem esterification. Cov catalyst feem ntau yog cov kua qaub. Thiab tseem, cua sov yuav tsum tau muab los ua lub zog. Txwv tsis pub, yuav tsis muaj qhov tshwm sim ntawm carboxylic acid thiab cawv.
Dej yog tsim los ntawm cov khoom lag luam thaum lub sijhawm esterification. Cov pab pawg -OH tshem tawm ntawm carboxylic acid thiab -H pawg tshem tawm ntawm cawv, ua ke tsim cov dej molecule (H-OH). Los ntawm kev hloov cov cawv los yog carboxylic acid, tuaj yeem tau txais cov esters nrog cov lej ntawm cov pa roj carbon atoms.
Cov tshuaj tiv thaiv esterification yog qhov sib npaug ntawm cov tshuaj reactants thiab cov khoom. Yog li ntawd, kev siv cov reactants ntau ntau ua rau muaj txiaj ntsig zoo ntawm ester nrog rau cov dej. Cov tshuaj dehydrating tuaj yeem siv los tshem tawm cov dej tsim. Thiab tseem, txoj kev tshaj lij xws li distillation kuj tseem siv tau rau kev tshem tawm dej.
Daim duab 01: Ester Formation
Esterification Mechanism
Nyob rau hauv cov txheej txheem esterification, ua ntej, kev tshem tawm -OH ntawm carboxylic acid thiab tshem tawm -H (proton) los ntawm cawv tshwm sim. Qhov no ua rau carboxylic cation thiab cawv nucleophile. Ob yam khoom no tuaj yeem cuam tshuam nrog ib leeg tsim cov ester. Cov pab pawg raug tshem tawm ua rau ib leeg ua dej.
Dab tsi yog Transesterification?
Transesterification yog txheej txheem siv los hloov cov qauv ntawm ester. Nws suav nrog ester thiab cawv ua cov tshuaj reactants. Lub transesterification tshwm sim thaum pawg alkyl ntawm ib qho ester pauv nrog cov pab pawg alkyl ntawm cawv. Nyob ntawd, cov cawv ua raws li ib tug nucleophile. Cov txheej txheem yuav tsum muaj cov catalyst; yog ib tug acidic catalyst los yog ib tug yooj yim catalyst. Cov catalyst tuaj yeem txo qhov kev ua kom lub zog thaiv ntawm cov txheej txheem.
Daim duab 02: Transesterification txheej txheem
Transesterification Mechanism
Ua ntej, cov cawv tau hloov mus rau hauv nucleophile los ntawm kev tshem tawm lub davhlau ya nyob twg hydrogen atom ua proton. Lub transesterification pib nrog kev tawm tsam nucleophilic; cawv tawm tsam cov pa roj carbon atom ntawm ester uas yog sib koom ua ke rau ob lub atoms oxygen. Qhov ntawd yog vim tias cov pa roj carbon atom no muaj ib feem zoo ntawm nws vim tias ob lub pa oxygen atom nyiam cov khoom siv hluav taws xob rau lawv (cov pa atoms yog cov electronegative ntau dua li carbon atoms).
Kev tawm tsam los ntawm cawv nucleophile ua rau tsim cov tshuaj nruab nrab uas muaj ob qho tib si ester thiab cawv sib koom ua ke los ntawm cov pa roj carbon atom tawm tsam los ntawm nucleophile. Qhov no intermediate compound yog heev unstable. Nyob ntawd, ib qho kev hloov kho tau tshwm sim kom tau txais daim ntawv ruaj khov. Qhov no muab ib daim ntawv ester tshiab. Transesterification muab cov nucleophile ua cov khoom lag luam.
Qhov txawv ntawm Esterification thiab Transesterification yog dab tsi?
Esterification vs Transesterification |
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| Esterification yog txheej txheem ntawm kev tsim cov ester los ntawm carboxylic acid thiab cawv. | Transesterification yog txheej txheem siv los hloov cov qauv ntawm ester. |
| Siv Ester | |
| In esterification, ester yog cov khoom tseem ceeb. | Nyob rau hauv transesterification, ester yog siv los ua reactant.. |
| Byproduct | |
| Esterification muab dej raws li cov khoom lag luam. | Transesterification muab cov nucleophile ua cov khoom lag luam. |
| Catalyst | |
| Esterification yuav tsum muaj cov kua qaub catalyst. | Transesterification yuav tsum muaj acidic lossis ib qho yooj yim catalyst. |
| Zoo Source | |
| Esterification yuav tsum tau cua sov ua lub zog. | Transesterification tsis xav tau lub zog. |
Summary – Esterification vs Transesterification
Esterification yog tsim los ntawm ester ntawm carboxylic acids thiab cawv. Transesterification yog cov txheej txheem ntawm kev hloov kho ntawm cov esters tsim. Qhov txawv ntawm esterification thiab transesterification yog qhov ester yog tsim los ntawm esterification whereas ester yog ib qho reactant hauv transesterification.
