Ngā Ārani: Te Hanganga me ngā Tauhohenga i roto i te Matū Waro
Pendahuluan
Ko ngā ārikana te rōpū māmā rawa o ngā warowaihā kua kōtui i roto i te matū waro. Ko ngā ngota waro (C) me te hauwai (H) anake e honoa ana e ngā hononga sigma kotahi (σ) kei roto. Mā te tātai whānui CₙH₂ₙ₊₂ mō ngā pūhui aliphatic, ka kiia ngā ārikana he paraffins, inā koa i roto i te umanga hinu me te hau. I roto i tēnei tuhinga, ka tūhuratia e mātou te hanganga, te whakaingoa, ngā āhuatanga ā-tinana me te matū, me ngā tauhohenga matua e pā ana ki ngā ārikana.
Hanganga me te Ingoa
He mekameka waro kei ngā ārikana, ā, ka taea te rārangi, te peka rānei. He sp³ te whakaranu o ngā ngota waro i roto i ngā ārikana, arā, e whā ngā hononga koha kotahi e hangaia ana e ia ngota waro, ka hua ake he hanganga tetrahedral me ngā koki hononga tata ki te 109.5°.
Ko te whakaingoatanga IUPAC (International Union of Pure and Applied Chemistry) mō ngā alkane e ahu mai ana i te maha o ngā ngota waro i roto i te mekameka tuarā. Kei te ripanga e whai ake nei ētahi tauira:
– Methane (CH₄): kotahi te ngota waro
– Etāne (C₂H₆): e rua ngā ngota waro
– Poropana (C₃H₈): e toru ngā ngota waro
– Pūtāne (C₄H₁₀): e whā ngā ngota waro
– Pentane (C₅H₁₂): e rima ngā ngota waro
Mena he nui atu i te whā ngā ngota waro o te mekameka matua, ka whakamahia he huinga ingoa e ai ki te maha o ngā ngota waro (hei tauira, ko te hexane te ingoa mō te ono, ko te heptane te ingoa mō te whitu, me ētahi atu).
Mō ngā alkane peka, ka tīmata te tatau i te pito o te mekameka e tata ana ki te peka. Ko ēnei peka, ko ngā whakakapinga rānei, ka tohua mā roto i ngā ingoa alkyl, hei tauira, te methyl (-CH₃) te ethyl rānei (-C₂H₅), ā, ko tō rātou tūranga i roto i te mekameka waro matua ka tohua mā roto i ngā tau. Ko tētahi tauira māmā ko te 2-methylpropane (C₄H₁₀), e mōhiotia ana ko te isobutane.
Ngā Āhuatanga Ā-tinana
Ko ngā ārani he kore-pōraruraru nā te mea he iti noa te rerekētanga o te irahiko o ngā hononga C-H. Nō reira, ka wairewa i roto i ngā whakarewa kore-pōraruraru engari kāore e wairewa i roto i te wai. Hei warowaihā kukū, ka piki ake ō rātou ira rewa me te kohua me te piki haere o te roa o te mekameka waro me te papatipu ngota. Hei tauira, ko te methane, te ethane, me te propane he hau i te pāmahana rūma, ko te butane me te pentane he wai, ā, ko ngā ārani he roa ake ngā mekameka ka taea te noho totoka i ngā āhuatanga paerewa.
Ko tētahi atu āhuatanga ā-tinana nui ko te mātotoru. He iti ake te mātotoru o ngā ārani i te wai (1 karamu/cm³), arā, ka mānu ina whakanohoia ki roto i te wai. Hei tāpiri, he iti te taupū whakaata o ngā ārani, ā, kāore e taunekeneke ki te mārama ultraviolet, ki te mārama kitea rānei.
Ngā Āhuatanga Matū me ngā Tauhohenga
I roto i ngā āhuatanga matū, he iti ake te tauhohenga o ngā alkana i ngā warowaihā kore-māku pērā i ngā alkene me ngā alkyne. Heoi anō, he maha ngā momo tauhohenga nui:
1. Te tahunga: Ka tauhohe ngā ārani ki te hāora (O₂) i roto i te tauhohenga tahunga hei whakaputa i te hauhā waro (CO₂), te wai (H₂O), me te pūngao. Ka taea te whakaatu i tēnei tauhohenga penei:
\[ \text{C}_n\text{H}_{2n+2} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{Pūngao} \]
Ka puta te tahunga katoa ina nui te hāora, engari ka puta te hauota waro (CO) me te waro (ngā pungarehu) i te tahunga kāore i oti.
2. Te Whakakapinga Rautaki: I raro i ētahi āhuatanga, ka taea e ngā alkana te tauhohe ki ngā halogen mā te tikanga rautaki kore utu. Hei tauira, ko te whakakōroi i te methane, e toru ngā wāhanga e puta ana: te tīmatanga, te horapa, me te whakamutu, ka puta ko te chloromethane (CH₃Cl) hei hua matua:
\[ \text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl} \]
3. Te pakaru: Ka whakamahia tēnei tukanga i roto i te umanga matū hinu hei wawahi i ngā ngota alkane nui ake ki ngā ngota iti ake, tae atu ki ngā alkene me ngā alkane iti iho. He mea tino nui tēnei i roto i te hanga wahie me ētahi atu hua matū:
\[ \kuputuhi{C}_{10}\kuputuhi{H}_{22} \rightarrow \kuputuhi{C}_8\kuputuhi{H}_{18} + \kuputuhi{C}_2\kuputuhi{H}_4 \]
4. Te Whakakotahitanga: Ka taea te huri i ngā alkane rārangi ki ngā isomer peka mā te whakamahi i ngā whakakorikori waikawa. He mea nui tēnei i roto i te ahumahi hei whakapai ake i te kounga wahie nā te mea he teitei ake ngā whakatauranga octane o ngā alkane peka.
Te Whakamahinga o ngā Alkanes
He whānuitia ngā whakamahinga o ngā ārani i roto i te oranga o ia rā me te ahumahi:
– Wahie: Ka whakamahia te methane, te ethane, te propane, me te butane hei hau māori me te wahie wai. Hei tauira, ka whakamahia te propane i roto i ngā pounamu hau mō te whakamahinga o te whare.
– Ngā Rauemi Mata Matū: Ko ngā ārani he rauemi mata mō te hanga kirihou, whakarewa, me ētahi atu hua matū mā roto i ngā tukanga matū pēnei i te pakaru me te whakapūhui.
– Ngā Hinu Whakahinuhinu me ngā Ware: Ka whakamahia ngā alkane mekameka roa i roto i ngā hinu whakahinuhinu me ngā ware nā te mea he āhuatanga whakahinuhinu me ngā ira rewa teitei.
Whakamutunga
Ko ngā ārikana he wāhanga matua o te matū waro, ā, he mahi nui tā rātou i roto i te ahumahi. Mai i tō rātou hanganga taketake me te whakaingoatanga ki ō rātou tauhohenga me ngā tono mahi, he mea nui te māramatanga hōhonu ki ngā ārikana. Nā te iti o te tauhohenga ka whai hua, engari he uaua hoki, i roto i ngā tono matū. Mā roto i ngā tikanga me ngā auahatanga pēnei i te pakaru me te isomerization, ka taea e tātou te whakamahi i ngā āhuatanga ahurei o ngā ārikana hei whakatutuki i ngā hiahia pūngao me ngā rauemi o te hapori hou.
Ahakoa te maha o ngā whakamahinga me te hiranga o ngā alkana, kei te haere tonu te rangahau me te tono mō ngā matū me ngā ahumahi.
