Aldehydes yog cov organic uas muaj cov pa roj carbonyl pawg >С=O ua khi rau tsawg kawg ib lub atom hydrogen. Aldehydes, nrog rau ketones zoo ib yam li lawv hauv cov qauv thiab cov khoom, hu ua carbonyl, lossis oxo compounds. Piv txwv ntawm aldehydes yog formic, acetic, propionic aldehyde.
Nomenclature
Cov npe tsis tseem ceeb ntawm aldehydes yog tsim los ntawm cov npe tsis tseem ceeb ntawm cov carboxylic acids. Piv txwv ntawm aldehydes nrog cov npe muaj nyob hauv daim duab. Thawj tus neeg sawv cev ntawm homologous series ntawm aldehydes yog formic aldehyde, los yog formaldehyde, oxidation ntawm uas tsim formic acid. Tus neeg sawv cev thib ob yog acetaldehyde, acetaldehyde, oxidation uas ua rau acetic acid.
Raws li IUPAC nomenclature, pawg aldehyde yog qhia los ntawm lub ntsiab lus -al, uas tau ntxiv rau lub npe ntawm cov hydrocarbon sib raug. Piv txwv ntawm aldehydes raws li IUPAC nomenclature tau pom zoo hauv daim duab hauv qab no.
Yog incompound muaj cov pab pawg laus, piv txwv li, pawg carboxyl, tom qab ntawd lub xub ntiag ntawm ib pawg aldehyde yog qhia los ntawm cov ntawv ua ntej formyl. Ib qho piv txwv ntawm aldehyde, uas yog hu ua dicarboxylic acid:
NEOS – CH (SNO) – CH2 – COOH
No yog 2-formylbutanedioic acid.
Kev piav qhia ntawm cov khoom
Aldehydes, tsis zoo li cawv, tsis muaj lub xov tooj ntawm tes hydrogen atom, yog li lawv cov molecules tsis koom nrog, uas piav qhia cov ntsiab lus qis dua. Piv txwv li, aldehyde formaldehyde boils twb kub ntawm -21 ° C, thiab cawv methanol ntawm +65 ° C.
Txawm li cas los xij, tsuas yog formaldehyde muaj qhov kub siab qis, tus neeg sawv cev tom ntej, acetaldehyde, boils ntawm +21 ° C. Yog li ntawd, nyob rau hauv chav tsev kub, ntawm tag nrho cov aldehydes, tsuas yog formaldehyde yog ib tug roj, acetaldehyde yog ib tug heev volatile kua. Ib qho kev nce ntawm cov pa roj carbon atom ib txwm ua rau qhov kub thiab txias. Yog li, benzaldehyde C6H5CHO boils xwb ntawm +180 ° C. Chain branching ua rau lub boiling point poob.
qis aldehydes, xws li formaldehyde, yog soluble hauv dej heev. Ib qho 40% tov ntawm formaldehyde yog hu ua formalin thiab feem ntau yog siv los khaws cov tshuaj lom neeg. Cov aldehydes siab dua yog soluble hauv cov kuab tshuaj organic - cawv, ether.
yam ntxwv tsw ntawm aldehydes
Aldehydes muaj cov yam ntxwv tsw, thiab cov qis qis yog ntse, tsis kaj siab. Txhua leej txhua tus paub qhov tsis hnov tsw ntawm formalin - ib tug aqueous tov ntawm formaldehyde. Siab aldehydes muaj floral tsw thiab siv nyob rau hauvtshuaj tsw qab.
Piv txwv ntawm aldehydes - cov khoom uas muaj ntxhiab tsw qab ntxiag - yog vanillin, uas muaj cov aroma ntawm vanilla, thiab benzaldehyde, uas muab cov yam ntxwv aroma ntawm almonds. Ob qho tshuaj no tau txais cov khoom siv hluavtaws thiab tau siv dav los ua cov khoom qab zib hauv kev lag luam khoom qab zib thiab naj hoom.
Tau txais
Cia peb xav txog txoj hauv kev kom tau txais aldehydes.
Oxidation ntawm cawv
Aldehydes yog tsim los ntawm oxidation ntawm thawj cawv. Piv txwv li, formaldehyde, uas yog siv nyob rau hauv zus tau tej cov ntaub ntawv polymeric, tshuaj, dyes, explosives. Hauv kev lag luam, formaldehyde yog tau los ntawm oxidation ntawm methanol nrog oxygen: 2 O.
Cov tshuaj tiv thaiv yog nqa tawm ntawm daim phiaj nyiaj kub, nyiaj yog lub catalyst. Methanol vapor tov nrog cua yog dhau los ntawm daim phiaj. Cov tshuaj tiv thaiv pib nrog kev tso tawm ntawm cov cua kub ntau, uas yog txaus kom cov kab sib chaws nyob rau hauv lub kub kub.
Dehydrogenation ntawm cawv
Aldehydes tuaj yeem tau los ntawm cawv thaum tsis muaj oxygen. Nyob rau hauv rooj plaub no, ib tug tooj liab catalyst thiab kub siab (250 ° C) yog siv: R-CH2-OH=R-CHO + H2..
Rov qab cov kua qaub chlorides
Aldehydes tuaj yeem tau txais los ntawm kev txo qis hydrogen ntawm cov kua qaub chlorides. "Poisoned" palladium yog siv los ua catalyst - nrog txo kev ua haujlwm: RClO + H2=RCHO + HCl.
Kev tsim cov acetaldehyde
Acetaldehyde yog tsim los ntawm oxidation ntawm ethylene nrog oxygen lossiscua hauv cov kua theem. Palladium chloride yuav tsum tau ua raws li catalyst (PdCl2): 2 CH2=CH2 + O2=2 CH3 CHO.
tshuaj muaj zog
Cov tshuaj tiv thaiv hauv qab no yog qhov raug rau aldehydes:
- carbonyl ntxiv;
- polymerization;
- kev sib tw;
- txo qis thiab oxidation.
Feem ntau cov kev tshwm sim tshwm sim los ntawm cov txheej txheem ntawm nucleophilic ntxiv rau C=O daim ntawv cog lus.
Feem ntau xav txog cov khoom siv tshuaj ntawm aldehydes siv piv txwv ntawm acetaldehyde.
Ntxiv cov tshuaj tiv thaiv
Nyob rau hauv pawg carbonyl C=O, cov electron ceev yog hloov mus rau oxygen atom, yog li ib feem zoo nqi yog tsim nyob rau hauv carbonyl carbon atom, uas txiav txim siab cov tshuaj ua si ntawm aldehydes. Tus nqi zoo ntawm cov pa roj carbon atom ntawm pawg C=O ua kom nws cov haujlwm hauv kev cuam tshuam nrog nucleophilic reagents - dej, cawv, magnesium organic tebchaw. Cov pa oxygen atom ntawm dej tuaj yeem tua cov carbonyl carbon atom, txuas rau nws thiab ua rau C=O daim ntawv cog lus tawg.
Cov tshuaj tiv thaiv kab mob
Aldehydes tau txais aldol thiab croton condensation tshwm sim.
Acetaldehyde nyob rau hauv qhov kev txiav txim ntawm cov tshuaj tsis muaj zog ntawm alkali nyob rau hauv txias hloov mus rau hauv aldol. Cov khoom siv tshuaj tiv thaiv yog cov kua miscible nrog dej nyob rau hauv lub siab txo. Cov tshuaj no muaj ob qho tib si aldehyde thiab ib pawg cawv (li no lub npe).
Cov tshuaj tiv thaiv zoo
Ob qhov zoo tshwm sim tuaj yeem siv los kuaj xyuas aldehydes:
Reaction of the "silver mirror". Cov tshuaj tiv thaiv pib nrog Tollens 'reagent - ammonia daws ntawm silver oxide. Thaum sib tov cov tshuaj ammonia thiab kev daws ntawm cov nyiaj nitrate, thawj qhov kev daws ntawm cov nyiaj hydroxide yog tsim, thiab thaum ntxiv ammonia ntau dhau, cov tshuaj diammine silver (I) hydroxide, uas yog tus neeg sawv cev oxidizing. Thaum sib cuam tshuam nrog aldehyde, lub ntsiab nyiaj yog tso tawm nyob rau hauv daim ntawv ntawm ib tug dub precipitate. Yog tias cov tshuaj tiv thaiv tau ua nrog cua sov qeeb, yam tsis tau co lub raj, cov nyiaj yuav npog cov phab ntsa ntawm lub raj, tsim kom muaj "daim iav" nyhuv
