Muaj ib qho sib xyaw: tartaric acid. Nws yog cov khoom pov tseg ntawm kev lag luam cawv. Thaum pib, tartaric acid muaj nyob rau hauv cov kua txiv hmab txiv ntoo nyob rau hauv daim ntawv ntawm nws acidic sodium ntsev. Txawm li cas los xij, thaum lub sij hawm fermentation txheej txheem, qab zib nyob rau hauv qhov kev txiav txim ntawm tshwj xeeb poov xab hloov mus rau hauv cawv, thiab los ntawm no lub solubility ntawm tartaric acid ntsev txo. Tom qab ntawd nws precipitates, uas yog hu ua tartar. Nws yog crystallized, acidified thiab, thaum kawg, cov kua qaub nws tus kheej tau txais. Txawm li cas los xij, tej yam tsis yooj yim nrog nws.
pasteur
Qhov tseeb, cov tshuaj muaj ob cov kua qaub: tartaric thiab lwm yam, txiv hmab. Lawv txawv nyob rau hauv uas tartaric acid muaj optical kev ua si (rotates lub dav hlau ntawm polarized lub teeb rau sab xis), thaum txiv hmab txiv ntoo acid tsis. Louis Pasteur tau tshawb xyuas qhov tshwm sim no thiab pom tias cov crystals tsim los ntawm txhua tus ntawm cov kua qaub yog daim iav duab ntawm ib leeg, uas yog, nws tau hais txog kev sib txuas ntawm cov duab ntawm cov muaju thiab cov khoom siv kho qhov muag. Nyob rau hauv 1848, tom qab ib tug series ntawm kev sim, nws tshaj tawm ib tug tshiab hom isomerism ntawm tartaric acids, uas nws hu ua enantiomerism..
Vant Hoff
Jacob van't Hoff tau qhia txog lub tswv yim ntawm qhov hu ua asymmetric (los yog chiral) carbon atom. Qhov no yog cov pa roj carbon uas tau sib koom ua ke rau plaub lub atoms sib txawv hauv cov organic molecule. Piv txwv li, nyob rau hauv tartaric acid, lub thib ob atom nyob rau hauv cov saw muaj ib tug carboxyl pawg nyob rau hauv nws cov neeg nyob ze,hydrogen, oxygen thiab ib qho thib ob ntawm tartaric acid. Txij li thaum nyob rau hauv no configuration carbon npaj nws daim ntawv cog lus nyob rau hauv daim ntawv ntawm ib tug tetrahedron, nws yog ib qhov ua tau kom tau txais ob lub tebchaw uas yuav yog daim iav dluab ntawm ib leeg, tab sis nws yuav tsis yooj yim sua kom "superpose" lawv nyob rau sab saum toj ntawm lwm yam tsis tau hloov lub kev txiav txim ntawm bonds nyob rau hauv lub molecule. Los ntawm txoj kev, txoj kev no los txhais chirality yog Tswv Kelvin lub tswv yim: cov zaub ntawm ib pawg ntawm cov ntsiab lus (nyob rau hauv peb cov ntaub ntawv, cov ntsiab lus yog atoms nyob rau hauv ib tug molecule) uas muaj chirality nyob rau hauv ib tug zoo tagnrho ca iav tsis tuaj yeem ua ke nrog cov pab pawg ntawm cov ntsiab lus nws tus kheej..
Symmetry ntawm molecules
Daim iav piav qhia zoo nkaus li yooj yim thiab zoo nkauj, tab sis nyob rau hauv niaj hnub organic chemistry, qhov twg cov molecules loj heev tau kawm, txoj kev xav no cuam tshuam nrog cov teeb meem loj. Yog li lawv tig mus ua lej. Los yog theej, symmetry. Muaj cov ntsiab lus symmetry - axis, dav hlau. Peb twist-twist lub molecule, tawm hauv lub symmetry ntsiab ruaj, thiab lub molecule, tom qab tig los ntawm ib tug tej lub kaum sab xis (360 °, 180 °, los yog lwm yam), pib saib raws nraim tib yam li thaum pib.
Thiab asymmetric carbon atom qhia los ntawm van't Hoff yog lub hauv paus ntawm qhov yooj yim tshaj plaws ntawm symmetry. Lub atom no yog lub chiral center ntawm lub molecule. Nws yog tetrahedral: nws muaj plaub daim ntawv cog lus nrog cov khoom sib txawv ntawm txhua tus. Thiab yog li ntawd, tig qhov kev sib txuas raws cov axis uas muaj xws li atom, peb yuav tau txais ib daim duab zoo tib yam nkaus xwb tom qab tag nrho kev sib hloov ntawm 360 °.
Feem ntau, qhov chaw chiral ntawm ib lub molecule tuaj yeem tsis yog ib qho xwbatom. Piv txwv li, muaj xws li ib tug nthuav compound - adamantane. Nws zoo li tetrahedron, nyob rau hauv uas txhua ntug yog ntxiv khoov rau sab nraud, thiab nyob rau hauv txhua lub ces kaum muaj carbon atom. Lub tetrahedron yog symmetrical txog nws qhov chaw, thiab yog li ntawm adamantane molecule. Thiab yog tias plaub qhov sib txawv hloov tau ntxiv rau plaub qhov "nodes" zoo tib yam ntawm adamantane, ces nws tseem yuav tau txais cov ntsiab lus symmetry. Tom qab tag nrho, yog tias koj tig nws txheeb ze rau nws sab hauv "qhov nruab nrab ntawm lub ntiajteb txawj nqus", daim duab yuav zoo sib xws nrog qhov pib tsuas yog tom qab 360 °. Ntawm no, es tsis txhob ntawm asymmetric atom, lub luag hauj lwm ntawm lub chiral center yog ua si los ntawm "kub" chaw ntawm adamantane.
Stereoisomers hauv bioorganic compounds
Chirality yog ib qho khoom tseem ceeb heev rau cov khoom siv roj ntsha. Tsuas yog isomers nrog qee cov qauv koom nrog hauv cov txheej txheem ntawm kev ua haujlwm tseem ceeb. Thiab yuav luag tag nrho cov khoom tseem ceeb rau lub cev yog npaj nyob rau hauv xws li ib txoj kev uas lawv muaj tsawg kawg yog ib qho chaw chiral. Cov piv txwv nrov tshaj plaws yog qab zib. Qhov ntawd yog glucose. Muaj rau carbon atoms nyob rau hauv nws cov saw hlau. Ntawm cov no, plaub lub atom muaj plaub qhov sib txawv ntawm ib sab ntawm lawv. Qhov no txhais tau hais tias muaj 16 qhov ua tau kho qhov muag isomers rau cov piam thaj. Tag nrho lawv tau muab faib ua ob pawg loj raws li kev teeb tsa ntawm asymmetric carbon atom ze tshaj plaws rau pawg cawv: D-saccharides thiab L-saccharides. Tsuas yog D-saccharides koom nrog hauv cov txheej txheem metabolic hauv lub cev muaj sia.
Teem ib qho piv txwv zoo rau stereoisomerism hauv bioorganic chemistry yog amino acids. Txhua yam ntuj tsimCov amino acids muaj cov amino pawg nyob ze ntawm cov pa roj carbon atom ze tshaj rau pawg carboxyl. Yog li, nyob rau hauv ib qho amino acid, lub atom no yuav asymmetric (ntau yam hloov pauv - carboxyl pawg, amino pawg, hydrogen thiab lwm cov saw; tshwj xeeb yog glycine nrog ob lub hydrogen atoms).
Raws li, raws li kev teeb tsa ntawm lub atom no, tag nrho cov amino acids kuj tau muab faib ua D-series thiab L-series, tsuas yog hauv cov txheej txheem ntuj, tsis zoo li cov suab thaj, L-series predominates.
