Ngā Waikawa me ngā Kawenga o Lewis: Te Ariā, Ngā Whakamahinga, me te Hiranga i roto i te Matū
Pendahuluan
I roto i te matū, kua mōhiotia, kua whakamahia hoki ngā ariā o ngā waikawa me ngā turanga mō ngā rautau. He maha ngā ariā kua whakawhanakehia hei whakamārama i ngā āhuatanga me te whanonga o ngā waikawa me ngā turanga. Ko tētahi ariā kua tino whai mana, ā, kua whānuitia te whakamahinga ko te ariā waikawa-turanga a Lewis. Ehara i te mea ka whānui ake i ngā whakamāramatanga o ngā waikawa me ngā turanga anake tēnei ariā, engari ka whakatakoto hoki i te huarahi mō te māramatanga hohonu ake ki te tauhohenga matū me ngā taunekeneke ngota. Ka matapakihia e tēnei tuhinga te ariā waikawa-turanga a Lewis, ōna tono, me tōna hiranga i roto i te matū.
Ngā Waikawa me ngā Kawenga o Lewis: Te Whakamāramatanga me ngā Ariā Taketake
I whakaurua te ariā waikawa-pūtake a Lewis e Gilbert N. Lewis i te tau 1923. He rerekē ki te ariā Bronsted-Lowry e tautuhi ana i ngā waikawa hei kaituku pūmua (H⁺) me ngā pūmua hei kaiwhiwhi pūmua, he whānui ake te huarahi e whakamahia ana e te ariā a Lewis mā te tautuhi i ngā waikawa me ngā pūmua i runga i ngā takirua irahiko:
– He momo matū te waikawa Lewis ka taea te tango i te takirua irahiko.
– He momo matū te turanga Lewis ka taea te tuku i te takirua irahiko.
Ko tētahi tauira māmā o te waikawa me te turanga Lewis ko te tauhohenga i waenga i te boron trifluoride (BF₃) me te haukini (NH₃). I roto i tēnei tauhohenga, ka mahi te BF₃ hei waikawa Lewis nā te mea he porowhita takoto kau tō te ngota boron ka taea te tango i tētahi takirua irahiko, ko te NH₃ ia ka mahi hei turanga Lewis nā te mea he takirua irahiko takitahi tō te ngota hauota ka taea e ia te tuku.
Hanganga me ngā Irahiko: Te Kī ki te Mārama ki ngā Waikawa me ngā Pātū o Lewis
Ko te tikanga, ka taea te whakamahi i te ariā hei whakamārama i ngā taunekeneke matū mā te tirotiro i te hanganga hiko o ngā ngota, ngā ngota rānei e whai wāhi ana. Ko ngā waikawa Lewis he momo me ngā porowhita kau, kua kore rānei e taupori, ka taea te kukume i ngā takirua irahiko mai i ngā turanga Lewis. Hei tauira:
– AlCl₃ (Konumohe trichloride): He waikawa Lewis a AlCl₃ nā te mea he porowhita kau tō te ngota konumohe ka taea te tango i ngā irahiko.
– H₂O (Wai): Mēnā he takirua irahiko takitahi kei runga i te hāora, ka taea e te wai te mahi hei turanga Lewis i roto i ngā tauhohenga maha.
Ka taea hoki e tēnei ariā te whakamārama i ngā pūhui matatini me ngā tauhohenga taunga matatini ake. Hei tauira, he maha ngā wā ka mahi ngā katote whakarewa whakawhiti hei waikawa Lewis i roto i ngā tauhohenga taunga, ka whakaae rātou i ngā takirua irahiko mai i ngā ligands e mahi ana hei turanga Lewis.
Ngā Whakamahinga o te Ariā Waikawa-Pūtake a Lewis i roto i te Matū
1. Te Hanganga Matū
I roto i te hanganga matū, he tino āwhina te ariā Lewis ki te hoahoa i ngā tauhohenga matū me te mārama ki ngā tikanga tauhohenga. Hei tauira, i roto i te tauhohenga Friedel-Crafts, ka mahi a AlCl₃ hei whakakorikori, ā, hei waikawa Lewis, ka āwhina i te hanganga o te matatini hiko e tika ana kia haere tonu ai te tauhohenga.
2. Matū Whakarite
Ko te matū taunga, e pā ana ki ngā matatini konganuku whakawhiti, he nui ngā painga mai i te ariā Lewis. Ko ngā konganuku whakawhiti he waikawa Lewis, he matatini hoki ki ngā ligands e tuku ana i ngā takirua irahiko. Mā te mārama ki ēnei taunekeneke ka taea e ngā kaimātai matū te hoahoa me te hanga i ngā momo matatini konganuku me ngā āhuatanga e hiahiatia ana.
3. Whakakorikori
He maha ngā tauhohenga whakatere e whakawhirinaki ana ki te mātāpono waikawa-pūtake Lewis. Hei tauira, ka whakamahia ngā whakatere waikawa Lewis i roto i te polymerization olefin, ka āwhina te whakatere i te tāpiri i ngā monomers ki te mekameka polymer e tipu haere ana. Ka whakamahia hoki tēnei ariā i roto i te hoahoa whakatere mō ngā tauhohenga rauropi, pērā i te hauwai, te waikura, me te dehydrogenation.
4. Matū Waro
I roto i te matū waro, ka āwhina te ariā Lewis ki te mārama ki ngā tikanga tauhohenga. Hei tauira, i roto i te tauhohenga tāpiri nucleophilic ki te carbonyl, ka mahi te rōpū carbonyl hei waikawa Lewis, ko te nucleophile ia ka mahi hei turanga Lewis. He mea nui te mārama ki te hanganga me te tauhohenga o ēnei takawaenga mō te whakawhanake i ngā ara hanga waro whai hua.
Ngā Tauhohenga Waikawa-Pūtake a Lewis i roto i te Wairewa Wai
Ahakoa e whakamahia ana te ariā waikawa-pūtake a Lewis ki ngā tauhohenga i roto i te āhua hau, i ngā whakarewa kore-wai rānei, he mea nui anō hoki tōna whakamahinga i roto i ngā otinga wai. Hei tauira, ko te hanganga o ngā matatini irahiko i roto i te wai. Ko ētahi irahiko konganuku, pērā i te Fe³⁺, ka mahi hei waikawa Lewis kaha, ā, ka taea te mahi tahi me ngā ngota wai (ngā pūtake a Lewis) hei hanga matatini wai pērā i te [Fe(H₂O)₆]³⁺.
Ngā Wero me ngā Arotakenga o te Ariā Waikawa-Pūtake a Lewis
Ahakoa te whānui o te whakamahinga, kāore te ariā waikawa-pūtake a Lewis i te kore he whakahē me ngā herenga. Ko tētahi wero nui ko te whānui rawa o te ariā i ētahi wā, ā, kāore i te whakarato i ngā matapae tauanga pono i ngā wā katoa. Hei tāpiri, ko ētahi tauhohenga e peia ana e ētahi atu āhuatanga, pērā i ngā pānga steric, entropy rānei, kāore pea e tino whakamāramahia e te ariā a Lewis.
1. Te Kore o te Ine Tau
He rerekē ki te ariā Bronsted-Lowry, e taea ai te ine mā te whakamahi i ngā uara pKa, kāore he inenga tauanga ōrite o te kaha o te waikawa-pūtake o Lewis. Nā tēnei ka uaua ki te whakatairite i te kaha o ngā waikawa, o ngā pūtake rānei i roto i ngā horopaki rerekē.
2. Te Māmā Rawa
Nā te mea ka tautuhia ngā waikawa me ngā kawakore i runga i te whakaae me te tuku takirua irahiko anake, e whakaarohia ana i ētahi wā ka whakangawarihia e tēnei ariā ngā taunekeneke matū uaua ake, inā koa i roto i ngā pūnaha koiora, i ngā rauemi rānei e whakaatu ana i ngā taunekeneke maha-āhuatanga.
Te Katinga
Ko te ariā waikawa-pūtake a Lewis tētahi pou matua o te matū hou. Nā ōna whakamāramatanga whānui me te ngāwari ake o ngā waikawa me ngā pūtake, ka taea e te ariā te mārama hohonu ki te whānuitanga o ngā tauhohenga matū, mai i te hanganga rauropi ki ngā matatini taunga whakarewa whakawhiti. Ahakoa ōna herenga, kei te whai tikanga tonu ngā tono o te ariā waikawa-pūtake a Lewis, ā, he mea nui tonu ki te rangahau me te whanaketanga matū e tipu haere tonu ana. Mā te whakamahinga tika me te māramatanga hohonu, ka noho tonu te ariā hei taputapu tino nui mā ngā kaimātai matū o te ao.
