Esters: general yam ntxwv thiab daim ntawv thov

Esters ntawm - hloov khoom ntawm hydrogen atoms ntawm lub hydroxyl pawg ntawm carboxylic acids thiab mineral acids ntawm cov pa roj carbon radical. Paub qhov txawv mono-, di- thiab polyesters. nyob mono, di- thiab polybasic acids, monobasic acids los - tag nrho thiab acid esters. Title ester muaj ib lub npe, muab kev koom tes nyob rau hauv nws tsim ntawm acid thiab dej caw. Rau esters, nquag siv no tsis tseem ceeb los yog keeb kwm nomenclature. Raws li IUPAC nomenclature npe esters yog tsim raws li nram no: muab ib tug tshaj dhau title cawv ntxiv raws li ib tug hydrocarbon acids lub npe thiab xaus -oat. Piv txwv li, lub yam ntxwv qauv ntawm esters (thiab isomers metamers) coj mus rau lub molecular mis S4N802, los ntawm txawv nomenclatures muaj npe: propilformiat (propilmetanoat) izopropilformiat (izopripilmetanoat), ethyl acetate (etiletanoat) melpropionat (methylpropanoate).

Kev npaj ntawm esters. Cov tebchaw lug faib nyob rau hauv cov xwm. Yog li, esters ntawm tsawg molecular nyhav thiab nruab nrab carboxylic acids homologous series yog ib feem ntawm qhov tseem ceeb roj ntawm ntau yam nroj tsuag (e.g., uksusnoizoamilovy ester los yog "txiv moj coos essence", uas yog ib feem ntawm lub pears thiab ntau xim), thiab esters ntawm glycerol thiab ntau dua fatty acids - tshuaj paus ntawm tag nrho cov roj thiab roj. Ib txhia esters yog npaj synthetically.

Lub esterification cov tshuaj tiv thaiv yuav siv sij hawm qhov chaw ntawm lub sis ntawm carboxylic (thiab mineral) acids nrog alcohols. Lub catalyst ua raws li ib tug muaj zog mineral acid (feem ntau siv H2S04). Lub catalyst molecule activates carboxylic acid.

Cov tshuaj tiv thaiv tus nqi ntawm esterification nyob kuj nyob rau hauv kab OH pab pawg neeg (rau cov thawj, theem nrab los yog tertiary) nrog rau tej carbon atom rau cov tshuaj xwm ntawm lub acid thiab haus dej haus cawv thiab cov hydrocarbon saw qauv, uas yog txuam nrog rau cov carboxyl.

Hydrolysis ntawm lub esters. Lub hydrolysis cov tshuaj tiv thaiv (saponification) esters - yog qhov rov qab cov tshuaj tiv thaiv ntawm esterification. Nws kis tau maj mam. Yog hais tias ntxiv rau cov tshuaj tiv thaiv sib tov, lub sib tov ntawm pob zeb hauv av acids los yog alkalis, nws tshaj tawm yuav tsub kom. Alkali saponification yuav siv sij hawm qhov chaw ib txhiab lub sij hawm sai tshaj li acids. Lub esters yog hydrolyzed nyob rau hauv ib tug alkaline nruab nrab, thiab ethers - nyob rau hauv acid.

Thaum cua kub esters nrog alcohols nyob rau hauv lub xub ntiag ntawm acid sulphate los yog alcoholates (alkaline nruab nrab) alkoxy pauv tshwm sim. Qhov no ntaub ntawv ib tug tshiab ester, thiab cov tshuaj tiv thaiv nruab nrab yog xa rov qab haus cawv, uas yav tas los yog nyob rau hauv daim ntawv ntawm cov residues nyob rau hauv lub ester molecule.

Esters yuav txo tau cov tshuaj tiv thaiv. Txo cov neeg ua hauj yog feem ntau lithium txhuas hydride, sodium nyob rau hauv boiling dej cawv. Esters siab kam mus rau lub kev txiav txim ntawm ntau yam oxidants siv nyob rau hauv cov tshuaj synthesis los yog tsom xam los tiv thaiv dej thiab phenolic pawg.

Esters ntsiab cov neeg sawv cev. Ethyl ethanoate (acetic ether) yog tau los ntawm cov esterification cov tshuaj tiv thaiv ntawm ethanol thiab acetate acid catalyst ( acid sulphate). Ethyl ethanoate yog siv raws li ib tug hnyav ntawm cellulose nitrate nyob rau hauv qhuav ntawm smokeless gunpowder, thiab photographic zaj duab xis, txiv hmab txiv ntoo essences yam rau cov zaub mov kev lag luam.

Izoamiletanoat (uksusnoizoamilovy ether, "txiv moj coos essence") yog ib co soluble nyob rau hauv ethanol, diethyl ether. Acetate twb npaj los ntawm esterification ntawm acids thiab isoamyl haus dej cawv. Izoamilmetilbutanoat siv raws li ib tug tsw tivthaiv nyob rau hauv perfumery thiab raws li ib tug hnyav.

Izoamilizovaleriat ( "Kua" essence, izovalerianovoizoamilovy ether) yog tau los ntawm reacting lub esterification isovaleric acid thiab isoamyl haus dej cawv. Hais tias ester yog siv raws li ib tug txiv hmab txiv ntoo essences nyob rau hauv lub lag luam ua noj.