Lub cev qhuav dej ntawm alcohols

Lub sij hawm "lub cev qhuav dej" yog siv nyob rau hauv cov tshuaj (lub ntsiab lus lub cev qhuav dej), nyob rau hauv chaw ua dav hlua (nws yog ib tug tsis muaj dej los ntawm lub dav hlau thaum lub sij hawm lub davhlau), nyob rau hauv Science News for KIDS (cov tshuaj tiv thaiv, uas tau ua los ntawm cov organic molecules phua tawm dej). Tshua ntawm alcohols lub cev qhuav dej cov yam ntxwv ntawm tebchaw yav tas los hu ua cawv. Cov txheej txheem tau nyaij los ntawm cua kub nyob rau hauv lub xub ntiag ntawm lub haus dej, uas yog sulfuric acid, zinc chloride, txhuas oxide los yog acid phosphoric. Nyob ntawm seb cov tshuaj tiv thaiv kev mob tej zaum yuav tsim unsaturated hydrocarbons, los yog ethers, nws yog muab faib thiab, raws li, rau intramolecular thiab intermolecular lub cev qhuav dej.

Ethers tsim thaum cov tshuaj tiv thaiv yog ua nyob ib sab kub thiab tshaj haus dej cawv. Nyob rau hauv thawj kauj ruam ntawm sulfuric acid ester yog tau: C2H5OH + HO-SO2OH ↔ C2H5O-SO2OH + H2O. Yog hais tias qhov tshuaj tiv thaiv sib tov yog ces sov, ces tsim ethylsulfuric acid yog reacted nrog ib tug dhau heev lawm ntawm cov cawv: C2H5O-SO2OH + C2H5OH → C2H5O-C2H5 + H2SO4. Cov no diethyl (los yog leej faj) ether. Raws li qhov no tswvyim hais intermolecular lub cev qhuav dej ntawm alcohols. Raws li ib tug tshwm sim, los ntawm nkauj nraug lub cawv los ntawm ob molecules ntawm ob hydrogen atoms thiab ib cov pa atom (lawv tsim ib tug dej molecule) tsim ethers. Nyob rau hauv kev lag luam, diethyl ether ua los ntawm xeem dhau tus dej cawv ntau tshaj ib tug khub ntawm txhuas oxide ntawm ib tug kub ntawm 250 ° C. Cov tshuaj tiv thaiv tswvyim yog raws li nram no: 2C2H5-OH → C2H5-O-C2H5 + H2O.

Intramolecular lub cev qhuav dej ntawm alcohols yuav tshwm sim tsuas yog nyob rau sov dua. Yog li los ntawm ib tug dej cawv molecule (es ob raws li nyob rau hauv lub yav dhau los cov ntaub ntawv) cais cov dej molecule thiab ob carbon atoms tsim los ntawm ib tug muab ob npaug rau daim ntawv cog lus. Siv tus qauv no rau qhov kev npaj ntawm unsaturated hydrocarbons. Siv rau lub hom phiaj no xwb monoalcohols. Piv txwv li, lub cleavage dej rau ethanol yog nqa tawm ntawm ib tug kub ntawm 500 ° C ntau tshaj ib tug dehydrating catalyst, e.g., alumina Al2O3 los yog zinc chloride ZnCl2.

Lub cev qhuav dej ntawm alcohols - yog ib tug yooj yim txoj kev rau cov ua gaseous alkenes nyob rau hauv lub lab. Nws yog siv rau zus tau tej cov ethylene los ntawm ethanol: CH3-CH2-OH → CH2 = CH2 + H2O. Lub cev qhuav dej yuav siv sij hawm qhov chaw nyob rau hauv lub xub ntiag ntawm ib lub hauv paus uas yog alumina. Officers ntawm ethyl cawv yog hla dhau rhuab alumina hmoov. Segregated dej absorbed li chav, yog li sawv ib tug dawb huv ethylene. Nyob rau hauv tus txheej txheem no, qhov zoo ntawm cov catalyst yuav siv concentrated acids, e.g., sulfuric los yog phosphoric. Lawv, xws li txhuas oxide, muaj lub dehydrating zog. Txawm li cas los, txij li thaum sulfuric acid kuj yog ib tug muaj zog oxidizing neeg sawv cev, nws ua ib tug ntau ntawm by-khoom (e.g., ib tug haus dej haus cawv yog oxidized rau carbon dioxide, thiab cov acid txo kom leej faj dioxide), li ntawd, lub ua roj yuav tsum tau ntxiv purification.

Lub cev qhuav dej ntawm alcohols ntawm cyclic qauv, e.g., lub cev qhuav dej ntawm cyclohexanol, tej zaum yuav siv sij hawm qhov chaw nyob rau hauv lub xub ntiag ntawm phosphoric acid. Nws yog feem ntau xav sulfuric acid, raws li nws yog, muaj zoo dehydrating zog, tsawg yuav pab mus rau tsim ntawm by-khoom, raws li zoo raws li ntau kev ruaj ntseg. Raws li ib tug ntawm xws li cov tshuaj tiv thaiv ua cyclohexene. Qhov tseeb hais tias cov pa roj carbon atoms ua ke nyob rau hauv lub nplhaib tsis hloov lub Science News for KIDS ntawm cov tshuaj tiv thaiv: C6H11-OH → C6H10 + H2O. Cyclohexanol yog rhuab nrog concentrated phosphoric (V) acid. Cov uas ua cyclic hydrocarbon muaj ib tug muab ob npaug rau daim ntawv cog lus nyob rau hauv lub nplhaib yog ib tug kua yeeb tshuaj, txawm li cas los rau cov purification los ntawm impurities nws yog distilled.

Nws tseem yog tau lub cev qhuav dej ntawm alcohols muaj nyob rau hauv ib tug qauv ntau hydroxyl pawg. Raws li ib qho piv txwv rau cov polyhydric alcohols yuav xav txog cov tshuaj tiv thaiv tau nyob rau hauv lub tshem tawm ntawm ob molecules ntawm cov dej los ntawm ob molecules ntawm ethylene glycol, li no txoj kev ua ib cyclic ether, dioxane: 2OH-CH2-CH2-OH → (C2H4O) 2. Lub cev qhuav dej yog thaum lub sij hawm lub distillation ntawm ethylene glycol nyob rau hauv lub xub ntiag ntawm sulfuric acid. Qhov no yog ib tug ntawm cov muaj yees ntawm kev txais tos ntawm dioxane.

Yog li, peb yuav hais tias cov lub cev qhuav dej ntawm alcohols thiab muaj muaj thiab kuaj daim ntaub ntawv. Raws li ib tug tshwm sim, tshuaj tebchaw yog tsim, uas yog siv rau cov kev tshawb fawb, raws li zoo raws li cov ntaub ntawv raw los yog koom haum pab reagents rau tshuaj lom neeg kev lag luam.