Alkenes yog cov khoom muaj txiaj ntsig "hloov pauv". Nrog lawv cov kev pab, koj tuaj yeem tau txais alkanes, alkynes, halogen derivatives, cawv, polymers thiab lwm yam. Qhov teeb meem tseem ceeb ntawm unsaturated hydrocarbons yog lawv yuav luag tag tsis muaj nyob rau hauv qhov; rau feem ntau, cov khoom ntawm no xyov series yog mined nyob rau hauv lub laboratory los ntawm cov tshuaj synthesis. Txhawm rau kom nkag siab txog cov yam ntxwv ntawm cov tshuaj tiv thaiv kom tau txais alkenes, koj yuav tsum nkag siab lawv cov qauv.
Alkenes yog dab tsi?
Alkenes yog cov organic uas muaj carbon thiab hydrogen atoms. Ib tug feature ntawm no series yog ob tug covalent bonds: sigma thiab pi. Lawv txiav txim siab txog tshuaj thiab lub cev ntawm cov khoom. Lawv cov ntsiab lus melting yog qis dua li ntawm cov alkanes sib raug. Tsis tas li ntawd, alkenes txawv ntawm qhov "pab" series ntawm hydrocarbons los ntawm qhov muaj cov tshuaj tiv thaiv ntxiv, uas tshwm sim los ntawm kev rhuav tshem pi daim ntawv cog lus. Lawv muaj plaub hom isomerism:
- raws li txoj haujlwm ntawm ob daim ntawv cog lus;
- rau kev hloov pauv ntawm cov pob txha pob txha;
- interclass (nrog cycloalkanes);
- geometric (cis- thiab trans-).
Lwm lub npe rau qhov noib tug xov tooj ntawm cov khoom - olefins. Qhov no yog vim lawv qhov zoo sib xws nrog polyhydric carboxylic acids, uas muaj ob daim ntawv cog lus hauv lawv cov muaj pes tsawg leeg. Lub nomenclature ntawm alkenes txawv nyob rau hauv hais tias thawj atom nyob rau hauv cov pa roj carbon saw yog txiav txim los ntawm qhov chaw ntawm ib tug ntau yam daim ntawv cog lus, txoj hauj lwm ntawm uas kuj qhia nyob rau hauv lub npe ntawm cov khoom.
Cracking yog txoj hauv kev tseem ceeb rau rho tawm alkenes
Cracking yog hom roj refining ntawm qhov kub thiab txias. Lub hom phiaj tseem ceeb ntawm cov txheej txheem no yog kev rho tawm cov khoom uas muaj qhov hnyav dua molecular. Kev tawg los tsim alkenes tshwm sim thaum lub sij hawm tawg ntawm alkanes, uas yog ib feem ntawm cov khoom siv roj av. Qhov no tshwm sim ntawm qhov kub ntawm 400 txog 700 ° C. Nyob rau hauv cov chav kawm ntawm cov tshuaj tiv thaiv no kom tau txais alkenes, ntxiv rau cov khoom uas yog lub hom phiaj ntawm nws qhov kev siv, ib qho alkane yog tsim. Tag nrho cov pa roj carbon atoms ua ntej thiab tom qab cov tshuaj tiv thaiv yog tib yam.
Lwm txoj kev lag luam kom tau txais alkenes
Koj tsis tuaj yeem tham ntxiv txog alkenes yam tsis tau hais txog cov tshuaj tiv thaiv dehydrogenation. Rau nws qhov kev siv, ib qho alkane yog coj, uas ob daim ntawv cog lus tuaj yeem tsim tom qab tshem tawm ntawm ob lub hydrogen atoms. Ntawd yog, methane yuav tsis nkag mus rau hauv cov tshuaj tiv thaiv no. Yog li ntawd, ib tug xov tooj ntawm alkenes pib los ntawm ethylene. Tshwj xeeb tej yam kev mob rau cov tshuaj tiv thaiv yog siab kub thiab ib tug catalyst. Nickel lossis chromium (III) oxide tuaj yeem ua raws li tom kawg. Qhov tshwm sim ntawm cov tshuaj tiv thaiv yuav yog ib qho alkene nrog tus naj npawb ntawm cov pa roj carbon atoms thiab cov roj tsis muaj xim (hydrogen).
Lwm txoj kev lag luam kom tau txais cov tshuaj ntawm cov koob no yog hydrogenation ntawm alkynes. Cov tshuaj tiv thaiv no kom tau txais alkenes tshwm sim ntawm qhov kub thiab txias thiab nrog kev koom tes ntawm cov catalyst (nickel lossis platinum). Lub tshuab hydrogenation yog ua raws li kev rhuav tshem ib qho ntawm ob daim ntawv cog lus ntawm alkyne, tom qab uas hydrogen atoms ntxiv rau ntawm qhov chaw ntawm kev puas tsuaj.
Lab txoj kev siv cawv
Ib txoj hauv kev yooj yim tshaj plaws thiab pheej yig tshaj plaws yog intramolecular dehydration, uas yog, tshem tawm cov dej. Thaum sau qhov sib npaug ntawm cov tshuaj tiv thaiv, nws tsim nyog nco ntsoov tias nws yuav ua raws li txoj cai Zaitsev: hydrogen yuav cais tawm ntawm qhov tsawg kawg nkaus hydrogenated carbon atom. Qhov kub yuav tsum siab tshaj 150 ° C. Raws li ib tug catalyst, koj yuav tsum tau siv cov khoom uas muaj hygroscopic zog (muaj peev xwm rub ya raws), piv txwv li, sulfuric acid. Ib daim ntawv cog lus ob zaug yuav tsim ntawm qhov chaw ntawm kev sib cais ntawm pawg hydroxyl thiab hydrogen. Qhov tshwm sim ntawm cov tshuaj tiv thaiv yuav yog qhov sib thooj alkene thiab ib qho dej molecule.
Laboratory-based halo derivatives
Muaj ob txoj hauv kev kuaj ntxiv. Thawj yog qhov kev txiav txim ntawm alkali tov ntawm alkane derivatives, uas muaj ib tug halogen atom nyob rau hauv lawv muaj pes tsawg leeg. Txoj kev no yog hu ua dehydrohalogenation, uas yog, tshem tawm cov tshuaj hydrogen nrog cov tsis yog xim hlau ntawm pawg xya (fluorine, bromine, chlorine, iodine). Kev siv cov tshuaj tiv thaiv mechanism, zoo li hauv cov ntaub ntawv dhau los, ua tiav raws li txoj caiZaitsev. Cov xwm txheej catalytic yog cov kua dej cawv thiab qhov kub siab. Tom qab cov tshuaj tiv thaiv, ib qho alkene, ntsev ntawm alkali hlau ntsiab thiab halogen, dej yog tsim.
Txoj kev thib ob zoo ib yam li yav dhau los. Nws yog nqa tawm siv ib qho alkane, uas muaj ob halogens nyob rau hauv nws muaj pes tsawg leeg. Cov khoom no cuam tshuam los ntawm cov hlau nquag (zinc lossis magnesium) nyob rau hauv muaj cov kua dej cawv thiab kub siab. Cov tshuaj tiv thaiv tsuas yog tshwm sim yog tias cov hydrogen hloov los ntawm halogen ntawm ob lub atoms nyob sib ze, yog tias qhov xwm txheej tsis tau ntsib, ces ob daim ntawv cog lus tsis tsim.
Vim li cas thiaj noj zinc thiab magnesium? Thaum lub sij hawm cov tshuaj tiv thaiv, cov hlau yog oxidized, uas tuaj yeem pub ob lub electrons, thiab ob lub halogens raug tshem tawm. Yog tias koj noj cov ntsiab lus alkaline, lawv yuav hnov mob nrog dej, uas yog ib feem ntawm cov kua dej cawv. Raws li rau cov hlau uas tom qab magnesium thiab zinc hauv Beketov series, lawv yuav tsis muaj zog heev.
