Qhov Tseem Ceeb - Alkanes vs Alkenes
Alkanes thiab Alkenes yog ob hom hydrocarbon tsev neeg uas muaj carbon thiab hydrogen hauv lawv cov qauv molecular. Qhov sib txawv tseem ceeb ntawm Alkanes thiab Alkenes yog lawv cov qauv tshuaj; alkanes yog saturated hydrocarbons nrog rau cov qauv molecular ntawm CnH2n + 2 thiab alkenes tau hais tias yog pawg tsis muaj hydrocarbon vim lawv muaj ob npaug. kev sib txuas ntawm ob lub pa roj carbon atom. Lawv muaj cov qauv molecular ntawm CnH2n.
Alkanes yog dab tsi?
Alkanes tsuas muaj ib daim ntawv cog lus ntawm Carbon thiab hydrogen atoms (C-C bonds thiab C-H bonds). Yog li ntawd, lawv hu ua "saturated hydrocarbons". Raws li tus qauv orbital hybridization, tag nrho cov carbon atoms hauv Alkenes muaj SP 3 hybridization. Lawv tsim sigma daim ntawv cog lus nrog Hydrogen atoms, thiab cov txiaj ntsig molecule muaj geometry ntawm tetrahedron. Alkanes tuaj yeem muab faib ua ob pawg raws li lawv cov kev npaj molecular; acyclic alkanes (CnH2n.+2) thiab cyclic alkanes (CnH 2n).
Alkenes yog dab tsi?
Alkenes yog cov hydrocarbons, muaj cov Carbon-Carbon (C=C) ob daim ntawv cog lus. "Olefins" yog lub npe qub siv los xa mus rau tsev neeg alkene. Cov tswv cuab tsawg tshaj plaws ntawm tsev neeg no yog ethane (C2H4); nws tau hu ua olefian t gas (Latin: 'oleum' txhais tau tias 'roj' + 'facere' txhais tau tias 'ua') nyob rau hauv thaum ntxov hnub. Qhov no yog vim cov tshuaj tiv thaiv ntawm C2H4 thiab chlorine muab C2H2 Cl2, roj.
Qhov txawv ntawm Alkanes thiab Alkenes yog dab tsi?
Tshuaj Txheej Txheem ntawm Alkanes thiab Alkenes
Alkanes: Alkanes muaj cov qauv molecular CnH2n+2. Methane (CH 4) yog qhov tsawg tshaj plaws alkane.
| Npe | tshuaj formula | Acyclic qauv |
| Methane | CH4 | CH4 |
| Ethane | C2H6 | |
| Propane | ||
| YButane | C4H10 | |
| Pentane | C5H12 | 3 |
| Hexane | C6H14 | CH3CH2CH2 CH2 CH2CH3 |
| Heptane | C7H16 | 2CH2CH3 |
| Octane | C8H18 | CH3CH3CH2CH2 CH2CH2CH3CH3 |
Alkenes: Alkenes muaj cov tshuaj formula ntawm CnH2n. Alkenes raug suav hais tias yog unsaturated hydrocarbons vim lawv tsis muaj ntau tshaj plaws ntawm Hydrogen atoms uas tuaj yeem muaj los ntawm hydrocarbon molecule.
| Npe | tshuaj formula | qauv |
| Ethene | CH2=CH2 | |
| Propene | C3H6 | CH3CH=CH2 |
| Butene | C4H8 | CH2=CHCH2CH3, CH 3 CH=CHCH3 |
| Pentene | C5H10 | CH2=CHCH2CH2CH3, CH3CH=CHCH2CH3 |
| Hexene | C6H12 |
CH2=CHCH2 CH2CH2 CH3CH3CH=CHCH2CH2 CH3 CH3CH2CH=CHCH2 CH3 |
| Heptene | C7H14 | CH=CHCH2CH2CH2 CH2CH3CH3CH2 CH2CH2CH2CH3 |
tshuaj muaj txiaj ntsig ntawm Alkanes thiab Alkenes
Alkanes:
Reactivity:
Alkanes yog inert rau ntau cov tshuaj reagents. Qhov no yog vim Carbon-Carbon (C-C) thiab Carbon - Hydrogen (C-H) bonds muaj zog heev vim Carbon thiab Hydrogen atoms muaj ze li ntawm tib electronegativity qhov tseem ceeb. Yog li ntawd, nws yog qhov nyuaj heev los rhuav tshem lawv cov ntawv cog lus, tshwj tsis yog tias lawv tau ua kom sov rau qhov kub siab.
Combustion:
Alkanes tuaj yeem hlawv hauv huab cua. Cov tshuaj tiv thaiv ntawm Alkanes nrog cov pa ntau dhau hu ua "combustion". Hauv cov tshuaj tiv thaiv no, alkanes hloov mus rau carbon dioxide (CO2) thiab dej.
CnH2n + (n + n/2) O2 → n CO2 + nH2O
C4H10 + 13/2 O2 → 4 CO 2+ 5H2O
Butane Oxygen Carbon Dioxide Dej
Cov tshuaj tiv thaiv combustion yog cov tshuaj tiv thaiv exothermic (lawv muab cua sov). Yog li ntawd, alkanes tau siv los ua lub zog.
Alkenes:
Reactivity:
Alkenes hnov mob nrog Hydrogen nyob rau hauv lub xub ntiag ntawm ib tug finely faib hlau catalyst los ua tus coj alkane. Tus nqi ntawm cov tshuaj tiv thaiv tsawg heev yam tsis muaj catalyst.
Catalytic hydrogenation yog siv hauv kev lag luam zaub mov los hloov cov roj zaub ua kua rau cov roj semi-solid hauv kev ua margarine thiab cov roj ua noj ua haus.
Lub cev muaj zog ntawm Alkanes thiab Alkenes
Forms
Alkanes: Alkanes muaj xws li roj, kua thiab cov khoom khib nyiab. Methane, ethane, propane thiab butane yog gases nyob rau hauv chav tsev kub. Cov qauv tsis sib xws ntawm hexane, pentane thiab heptane yog kua. Alkanes uas muaj qhov hnyav dua molecular yog cov khoom.
CH4 to C4H10 yog gases
C5H12 to C17H36 yog kua, thiab
Alkanes nrog qhov hnyav dua molecular yog cov khoom muag muag
Alkenes: Alkenes qhia txog lub cev zoo sib xws ntawm Alkane sib raug. Alkenes uas muaj qhov hnyav dua molecular (C 2 H 4 toC 4 H 8) yog cov roj cua ntawm chav tsev kub thiab cua txias. Alkenes muaj qhov hnyav dua molecular yog cov khoom.
Solubility:
Alkanes: Alkanes tsis yaj hauv dej. Lawv yog yaj nyob rau hauv tsis-polar los yog weakly polar organic solvents.
Alkenes: Alkenes yog cov polar molecules vim yog C=C daim ntawv cog lus; Yog li ntawd, lawv yog soluble nyob rau hauv non-polar solvents los yog cov kuab tshuaj ntawm polarity tsawg. Dej yog ib qho polar molecule thiab alkenes me ntsis soluble hauv dej.
Density:
Alkanes: Qhov ntom ntawm Alkanes qis dua qhov ntom ntawm cov dej. Lawv qhov ntom ntom yog ze li ntawm 0.7 g mL-1, xav txog qhov ntom ntawm dej li 1.0 g mL-1.
Alkenes: Qhov ntom ntawm Alkenes qis dua qhov ntom ntawm dej.
Cov ntsiab lus kub:
Alkanes: Lub ntsiab lus kub ntawm unbranched alkanes smoothly nce raws li tus naj npawb ntawm Carbon atoms thiab molecular hnyav nce. Feem ntau, cov ceg ntoo alkanes muaj cov ntsiab lus kub qis dua piv rau cov alkanes uas tsis muaj alkanes, muaj tib cov pa roj carbon atoms.
Alkenes: Cov ntsiab lus Boiling zoo ib yam li cov alkanes sib raug nrog qhov sib txawv me me.
