Ngaphezu Electrophilic e Organic Chemistry

Ukuze kwalokho ukusabela libhekene kumiswa zamakhemikhali kusukela ezimbili noma ngaphezulu sokuqala izinto. Cabanga indlela ye kwalokho electrophilic esibonelweni elula alkenes - unsaturated hydrocarbon acyclic nomunye isibopho double. Ngaphezu kwalokho kubo, e kugucuka abanjalo nezinye hydrocarbon kokuba izibopho amaningi, kuhlanganise eyindilinga.

Izigaba ukusabela amangqamuzana kokuqala

Ngaphezu Electrophilic senzeka ngezigaba eziningana. Electrophile kokuba omuhle icala lisebenza njengesimemo acceptor electron, futhi isibopho kabili i-molecule alkene - njengoba ukunikela ngezitho electron. Zezakhi amabili akha p-oluyingozi eziyinkimbinkimbi kuqala. Khona-ke iqala ekuguquleni π-eyinkimbinkimbi ϭ-eziyinkimbinkimbi. Carbocation kumiswa kulesigaba nokuzinza yayo ukuthola izinga yokusebenzisana jikelele. Ngemva kwalokho carbocation usabela ngokushesha nge ngokwengxenye nucleophile omubi icala kanye yokugcina ukuguqulwa umkhiqizo kwakhiwa.

Umthelela substituents ku izinga yokusabela

Shaja delocalization (ϭ +) e carbocation incike kokuqala ukwakheka kwama-molecule. Positive umphumela exhasa esizibonakalisa alkyl iqembu, kuholela ukwehla ophathwa eduze carbon athomu. Ngenxa yalokho, ngo-engqamuzaneni ne-electron ngokunikela substituent kwandisa ukuzinza eyisihlobo seka π-electron kwabantu kungenxa futhi reactivity engqamuzaneni iyonke. Effect phezu reactivity ka-electron acceptors kuyoba okuphambene.

Lo mshini halogens uxhumano

Ake sihlole kabanzi mshini kwalokho electrophilic we alkene ukuba isibonelo ukuxhumana kanye Halogen.

1. Halogen-molecule osondela isibopho double phakathi ama-athomu carbon futhi athuthukisiwe. Ngenxa icala kancane omuhle ngesikhathi esisodwa ekupheleni Halogen-molecule ukudansela isiginci sakhe electron π-bond. Njengoba kukhona ekumiseni engazinzile π-eziyinkimbinkimbi.
2. In the isinyathelo esilandelayo kuyizinhlayiyana electrophilic exhunywe kwi athomu amabili-carbon, likhula lakha isiyingi. Kukhona eyindilinga "onium" ion.
3. Asele icala kuyizinhlayiyana Halogen (nucleophile kahle icala) is wasithukuthelela ion onium nekungenelela ngakolunye uhlangothi kusukela odlule izinhlayiya Halogen. Ivela umkhiqizo wokugcina - Trans-1,2-digalogenalkan. Ngokufanayo, okunamathiselwe kwenzeka Halogen cycloalkenyl.

Mshini okunamathiselwe acid hydrohalic

Ngaphezu Electrophilic hydrogen halides futhi sulfuric acid zenzeka ngenye indlela. Endaweni esidi is ubuhlobo ibe seka futhi reagent anion. ion Kahle icala (electrophile) ehlasela π-isibopho oluhambisana komunye ukuzulazula kwama-athomu carbon. kwakhiwa Carbocation is, lapho eduze carbon athomu is kahle icala. carbocation Landelayo ixubana anion ukwakha umkhiqizo wokugcina ukuthi bayavuma.

I isiqondiso ukusabela phakathi reagents futhi Markovnikov ngokuvamile azilingani

Ngaphezu Electrophilic phakathi amangqamuzana ezimbili quin kwenzeka regioselectively. Lokhu kusho ukuthi kwakheka isomers amabili kungenzeka is mhlawumbe othile nje. Regioselectivity uchaza umthetho Markovnikov sika, owawuthi hydrogen kuxhunywe athomu carbon elixhumene Nenani elikhulu labanye ama-athomu ye-hydrogen (ngaphezulu hydrogenated).

Ukuze uqonde lo mthetho, kubalulekile ukukhumbula ukuthi izinga yokusabela incike ukuzinza carbocation Lesisemkhatsini. Umthelela electron donor futhi acceptor substituents eshiwo ngenhla. Ngakho, ngaphezu electrophilic ka hydrobromic acid propene kuholela ekwakhekeni kwe-2-bromopropane. I seka Lesisemkhatsini nenkokhiso elihle enkabeni carbon athomu ngaphezulu carbocation esitebeleni nenkokhiso omuhle nakuyi-athomu kakhulu. Ngenxa yalokho, i-athomu uxhumano lokudlulisa is asabela ngayo nge-carbon-athomu yesibili.

Umthelela substituents electron-ukuhoxa ngenkambo nokuxhumana

Uma i-molecule ye yokuqala iqukethe electron ukhipha substituent elinendawo exhasa ezimbi kanye / noma umphumela mesomeric, ngaphezu electrophilic kuphambene nemithetho ngenhla. Izibonelo substituents ezifana: CF _3, COOH, CN. Kulokhu, lo mkhulu ibanga icala omuhle eyinhloko electron ukhipha iqembu lenza carbocation uzinze ngokwengeziwe. Ngenxa yalokho, i-hydrogen exhunywe kwi-carbon-athomu kancane hydrogenated.

okufushane Universal wemithetho izobukeka kanje: nokuxhumana i alkene quin futhi quin reagent ukuphendula ukuqhutshwa ngendlela ukwakheka carbocation esitebeleni kunazo.