Li-Alkanes: Sebopeho le Likarabelo ho Khemistri ea Lintho tse Hloahloa
Pendahuluan
Li-alkane ke sehlopha se bonolo ka ho fetisisa sa li-hydrocarbon tse tletseng lik'hemik'haleng tsa lintho tse phelang. Li na le liathomo tsa carbon (C) le hydrogen (H) feela tse hokahaneng le libonto tse le 'ngoe tsa sigma (σ). Ka foromo e akaretsang ea CₙH₂ₙ₊₂ bakeng sa metsoako ea aliphatic, li-alkane hangata li bitsoa paraffin, haholo-holo indastering ea oli le khase. Sehloohong sena, re tla hlahloba sebopeho, mabitso a mabitso, thepa ea 'mele le ea lik'hemik'hale, le likarabelo tsa bohlokoa tse amanang le li-alkane.
Sebopeho le Lebitso la Mabitso
Li-alkane li na le liketane tsa khabone tse ka bang mola kapa makala. Liathomo tsa khabone tse li-alkane li kopantsoe ka sp³, ho bolelang hore athomo e 'ngoe le e 'ngoe ea khabone e etsa litlamo tse 'ne tse le' ngoe tsa covalent, e leng se fellang ka sebopeho sa tetrahedral se nang le likhutlo tsa tlamo tse ka bang 109.5°.
Lebitso la IUPAC (International Union of Pure and Applied Chemistry) bakeng sa li-alkanes le ipapisitse le palo ea liathomo tsa khabone tse ka har'a ketane ea mokokotlo. Tafole e latelang e fana ka mehlala e meng:
– Methane (CH₄): athomo e le 'ngoe ea khabone
– Ethane (C₂H₆): liathomo tse peli tsa khabone
– Propane (C₃H₈): liathomo tse tharo tsa khabone
– Butane (C₄H₁₀): liathomo tse 'ne tsa khabone
– Pentane (C₅H₁₂): liathomo tse hlano tsa khabone
Haeba ketane e kgolo e na le diathomo tse fetang tse nne tsa khabone, re sebedisa motswako wa mabitso ho ya ka palo ya diathomo tsa khabone (mohlala, hexane bakeng sa tse tsheletseng, heptane bakeng sa tse supileng, jj.).
Bakeng sa di-alkane tse nang le makala, ho ngolwa ha dinomoro ho qala qetellong ya ketane e haufi le lekala. Makala ana, kapa di-substituents, a kgethwa ka mabitso a alkyl, mohlala, methyl (-CH₃) kapa ethyl (-C₂H₅), mme boemo ba ona ketane e kgolo ya khabone bo bontshwa ke dinomoro. Mohlala o bonolo ke 2-methylpropane (C₄H₁₀), e tsejwang hape e le isobutane.
Matlotlo a 'Mele
Li-alkane li atisa ho se be polar hobane litlamo tsa C-H li na le phapang e nyane ea electronegativity. Ka lebaka leo, lia qhibiliha ka har'a li-solvent tse seng polar empa ha li qhibilihe ka metsing. Jwalo ka li-hydrocarbon tse tletseng, lintlha tsa tsona tsa ho qhibiliha le ho belisa lia eketseha ka bolelele ba ketane ea khabone le boima ba limolek'hule. Mohlala, methane, ethane le propane ke likhase mochesong oa kamore, ha butane le pentane e le metsi, 'me li-alkane tse nang le liketane tse telele e ka ba tse tiileng maemong a tloaelehileng.
Tšobotsi e 'ngoe ea bohlokoa ea 'mele ke ho ba le bongata. Li-alkane hangata ha li teteaneng ho feta metsi (1 g/cm³), ho bolelang hore lia phaphamala ha li kenngoa ka metsing. Ho feta moo, li-alkane li na le index e tlase ea refractive 'me ha li sebelisane le ultraviolet kapa khanya e bonahalang.
Thepa ea Lik'hemik'hale le Likarabelo
Ho ya ka dikhemikhale, di-alkanes di atisa ho ba le karabelo e fokolang ho feta di-hydrocarbon tse sa tlalang tse kang di-alkenes le di-alkynes. Leha ho le jwalo, ho na le mefuta e mmalwa ya bohlokwa ya dikarabelo:
1. Ho Chesoa: Li-alkane li arabela le oksijene (O₂) karabelong ea ho tuka ho hlahisa carbon dioxide (CO₂), metsi (H₂O), le matla. Karabelo ena e ka hlalosoa ka tsela ena:
\[ \text{C}_n\text{H}_{2n+2} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{Energy} \]
Ho cha ka ho feletseng ho etsahala ha oksijene e le ngata, athe ho cha ka ho sa fellang ho hlahisa carbon monoxide (CO) kapa esita le carbon (mosili).
2. Phetoho ea Radical: Tlas'a maemo a itseng, li-alkanes li ka arabela le li-halogen ka mokhoa oa free radical. Mohlala ke chlorination ea methane, e etsahalang ka mekhahlelo e meraro: ho qalisoa, ho ata le ho felisoa, ho hlahisa chloromethane (CH₃Cl) e le sehlahisoa se seholo:
\[ \text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl} \]
3. Ho petsoha: Ts'ebetso ena e sebediswa indastering ya peterole ho arola dimolek'hule tse kgolo tsa alkane hore e be tse nyane, ho kenyeletswa le di-alkene le di-alkane tse tlase. E bohlokwa haholo tlhahisong ya mafura le dihlahiswa tse ding tsa dikhemikhale:
\[ \text{C}_{10}\text{H}_{22} \rightarrow \text{C}_8\text{H}_{18} + \text{C}_2\text{H}_4 \]
4. Isomerization: Li-alkane tse otlolohileng li ka fetoloa li-isomer tse nang le makala ho sebelisoa li-catalyst tsa asiti. Sena se bohlokoa indastering ho ntlafatsa boleng ba mafura hobane li-alkane tse nang le makala li na le litekanyetso tse phahameng tsa octane.
Tšebeliso ea Li-Alkanes
Li-alkanes li na le mefuta e mengata ea lits'ebetso bophelong ba letsatsi le letsatsi le indastering:
– Mafura: Methane, ethane, propane le butane li sebelisoa e le khase ea tlhaho le mafura a metsi. Ka mohlala, propane e sebelisoa ka libotlolong tsa khase bakeng sa tšebeliso ea lelapa.
– Disebediswa tse Tala tsa Khemikhale: Di-alkane ke disebediswa tse tala bakeng sa tlhahiso ya dipolasetiki, di-solvent, le dihlahiswa tse ding tse fapaneng tsa dikhemikhale ka mekgwa ya dikhemikhale e kang ho petsoha le ho etsa polymerization.
– Litlolo le Boea: Li-alkane tse telele tsa ketane li sebelisoa litlolong le boea ka lebaka la thepa ea tsona ea ho tlotsa le libaka tse phahameng tsa ho qhibiliha.
Qetello
Li-alkane ke likarolo tsa bohlokoa tsa k'hemistri ea lintho tse phelang 'me li bapala karolo ea bohlokoa indastering. Ho tloha sebopehong sa tsona sa motheo le mabitso ho isa liketsong tsa tsona le lits'ebetsong tse sebetsang, kutloisiso e felletseng ea li-alkane ea bohlokoa. Hangata karabelo ea tsona e tlase e li etsa hore li be molemo, empa hape li be thata, lits'ebetsong tsa lik'hemik'hale. Ka mekhoa le boqapi bo kang ho petsoha le ho isomesa, re ka sebelisa thepa e ikhethang ea li-alkane ho fihlela litlhoko tsa matla le tsa thepa tsa sechaba sa sejoale-joale.
Ka lebaka la tšebeliso ea tsona e fapaneng le bohlokoa ba tsona, li-alkanes li ntse li tsoela pele ho ithutoa le ho sebelisoa k'hemistri le indastering.
