ʻAlkanes: ʻAno a me nā hopena i ka Kemika Organic
Pendahuluan
ʻO nā Alkanes ka hui maʻalahi loa o nā hydrocarbons saturated i ka kemika organik. Loaʻa iā lākou nā ʻātoma kalapona (C) a me hydrogen (H) wale nō i hoʻopili ʻia e nā pilina sigma (σ) hoʻokahi. Me ke ʻano maʻamau CₙH₂ₙ₊₂ no nā hui aliphatic, kapa pinepine ʻia nā alkanes he paraffins, ʻoi aku hoʻi i ka ʻoihana aila a me ke kinoea. Ma kēia ʻatikala, e ʻimi mākou i ke ʻano, ka nomenclature, nā waiwai kino a me nā kemika, a me nā hopena koʻikoʻi e pili ana i nā alkanes.
ʻAno a me ka Inoa
Loaʻa i nā Alkanes nā kaulahao kalapona i hiki ke linear a lālā paha. Ua hoʻohuihui ʻia nā ʻātoma kalapona i loko o nā alkanes i ka sp³, ʻo ia hoʻi, hoʻokumu kēlā me kēia ʻātoma kalapona i ʻehā mau pilina covalent hoʻokahi, e hopena ana i kahi ʻano tetrahedral me nā kihi pilina o kahi o 109.5°.
Hoʻokumu ʻia ka inoa IUPAC (International Union of Pure and Applied Chemistry) no nā alkanes ma ka helu o nā ʻātoma kalapona i loko o ke kaulahao iwi kuamoʻo. Hāʻawi ka papa ma lalo nei i kekahi mau laʻana:
– Methane (CH₄): hoʻokahi ʻātoma kalapona
– ʻEtane (C₂H₆): ʻelua mau ʻātoma kalapona
– Propane (C₃H₈): ʻekolu mau ʻātoma kalapona
– Butane (C₄H₁₀): ʻehā mau ʻātoma kalapona
– Pentane (C₅H₁₂): ʻelima mau ʻātoma kalapona
Inā ʻoi aku ma mua o ʻehā mau ʻātoma kalapona o ke kaulahao nui, hoʻohana mākou i ka hui pū ʻana o nā inoa e like me ka helu o nā ʻātoma kalapona (no ka laʻana, hexane no ʻeono, heptane no ʻehiku, a pēlā aku).
No nā alkanes lālā, hoʻomaka ka helu ʻana ma ka hopena o ke kaulahao kokoke loa i ka lālā. Ua kapa ʻia kēia mau lālā, a i ʻole nā mea pani, e nā inoa alkyl, no ka laʻana, methyl (-CH₃) a i ʻole ethyl (-C₂H₅), a ua hōʻike ʻia ko lākou kūlana ma ke kaulahao kalapona nui e nā helu. ʻO kahi laʻana maʻalahi ʻo 2-methylpropane (C₄H₁₀), i ʻike ʻia hoʻi ʻo isobutane.
Nā Waiwai Kino
ʻO nā Alkanes ke ʻano non-polar no ka mea he ʻokoʻa electronegativity liʻiliʻi ko nā pilina C-H. ʻO ka hopena, hiki ke hoʻoheheʻe ʻia i loko o nā solvents non-polar akā ʻaʻole hiki ke hoʻoheheʻe ʻia i ka wai. Ma ke ʻano he hydrocarbons saturated, piʻi ko lākou mau kiko heheʻe a me ka paila me ka hoʻonui ʻana i ka lōʻihi o ke kaulahao kalapona a me ka nui o ka molekala. No ka laʻana, he mau kinoea ka methane, ethane, a me ka propane ma ka mahana o ka lumi, ʻoiai he wai ka butane a me ka pentane, a hiki i nā alkanes me nā kaulahao lōʻihi ke lilo i mau mea paʻa ma nā kūlana maʻamau.
ʻO kekahi waiwai kino koʻikoʻi, ʻo ia ka nui. ʻOi aku ka liʻiliʻi o ka nui o nā Alkanes ma mua o ka wai (1 g/cm³), ʻo ia hoʻi ke lana nei lākou ke kau ʻia i loko o ka wai. Eia kekahi, he haʻahaʻa ka helu kuhikuhi refractive o nā alkanes a ʻaʻole lākou e launa pū me ka ultraviolet a i ʻole ka mālamalama ʻike ʻia.
Nā Waiwai Kemika a me nā Hana
Ma ke ʻano kemika, ʻoi aku ka liʻiliʻi o ka pane ʻana o nā alkanes ma mua o nā hydrocarbons unsaturated e like me nā alkenes a me nā alkynes. Eia nō naʻe, aia kekahi mau ʻano koʻikoʻi o nā hopena:
1. Ke kuni ʻana: Hana nā Alkanes me ka oxygen (O₂) i loko o kahi hopena kuni e hana i ke kalapona ʻokikene (CO₂), ka wai (H₂O), a me ka ikehu. Hiki ke hōʻike ʻia kēia hopena penei:
\[ \text{C}_n\text{H}_{2n+2} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{Ikehu} \]
Hana ʻia ka puhi piha ʻana ke lawa ka oxygen, ʻoiai ʻo ka puhi piha ʻole e hoʻopuka i ka carbon monoxide (CO) a i ʻole ke kalapona (soot).
2. Hoʻololi Radical: Ma lalo o kekahi mau kūlana, hiki i nā alkanes ke hana me nā halogens ma o kahi ʻano radical manuahi. ʻO kahi laʻana ka chlorination o ka methane, kahi e hana ʻia ma ʻekolu mau pae: hoʻomaka, hoʻolaha, a me ka hoʻopau ʻana, e hana ana i ka chloromethane (CH₃Cl) ma ke ʻano he huahana nui:
\[ \text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl} \]
3. Ka haki ʻana: Hoʻohana ʻia kēia kaʻina hana i ka ʻoihana petrochemical e wāwahi i nā molekala alkane nui i nā mea liʻiliʻi, me nā alkenes a me nā alkanes haʻahaʻa. He mea nui loa ia i ka hana ʻana i nā wahie a me nā huahana kemika ʻē aʻe:
\[ \kikokikona{C}_{10}\kikokikona{H}_{22} \rightarrow \kikokikona{C}_8\kikokikona{H}_{18} + \kikokikona{C}_2\kikokikona{H}_4 \]
4. Isomerization: Hiki ke hoʻololi ʻia nā alkanes linear i nā isomers lālā me ka hoʻohana ʻana i nā mea hoʻouluulu waikawa. He mea nui kēia i ka ʻoihana e hoʻomaikaʻi i ka maikaʻi o ka wahie no ka mea ʻoi aku ka kiʻekiʻe o nā helu octane o nā alkanes lālā.
Ka hoʻohana ʻana o nā Alkanes
He nui nā noi o nā Alkanes i ke ola o kēlā me kēia lā a me ka ʻoihana:
– Wahie: Hoʻohana ʻia ka Methane, ethane, propane, a me ka butane ma ke ʻano he kinoea kūlohelohe a me ka wahie wai. ʻO ka propane, no ka laʻana, hoʻohana ʻia i loko o nā ʻōmole kinoea no ka hoʻohana ʻana i ka home.
– Nā Mea Maka Kemika: ʻO nā Alkanes nā mea maka no ka hana ʻana i nā plastics, nā solvents, a me nā huahana kemika ʻē aʻe ma o nā kaʻina hana kemika e like me ka haki ʻana a me ka polymerization.
- Lubricants a me Waxes: Hoʻohana ʻia nā alkanes kaulahao lōʻihi i nā lubricants a me nā waxes ma muli o ko lākou mau waiwai lubricating a me nā kiko heheʻe kiʻekiʻe.
Ka hopena
ʻO nā Alkanes nā ʻāpana koʻikoʻi o ka kemika organik a he kuleana koʻikoʻi ko lākou i ka ʻoihana. Mai ko lākou ʻano kumu a me ka nomenclature a hiki i kā lākou mau hopena a me nā noi kūpono, he mea nui ka hoʻomaopopo piha ʻana i nā alkanes. ʻO kā lākou reactivity haʻahaʻa e hoʻolilo pinepine iā lākou i mea pono, akā paʻakikī hoʻi, i nā noi kemika. Ma o nā ʻenehana a me nā hana hou e like me ka haki ʻana a me ka isomerization, hiki iā mākou ke hoʻohana i nā waiwai kūikawā o nā alkanes e hoʻokō i ka ikehu a me nā pono o ke kaiāulu hou.
Me kā lākou hoʻohana like ʻole a me ke koʻikoʻi, ke hoʻomau nei nā alkanes i ke aʻo ʻana a me ka hoʻohana ʻana i ka kemika a me ka ʻoihana.
