Ukushintshwa ukusabela: incazelo, izibonelo kwesibalo

Abaningi esikhundleni ukuphendula engokwesiprofetho evula indlela yokuthola ukulungiswa compounds ahlukahlukene kokuba Umbuso isicelo. A indima enkulu kwezesayensi zamakhemikhali umkhakha kunikezwa esikhundleni electrophilic futhi nucleophilic. Ngo zamagama organic, lezi zinqubo benezingane eziningi izici kufanele kuqashelwe.

A ezihlukahlukene izenzakalo zamakhemikhali. esikhundleni ukuphendula

izinguquko Chemical elihlobene ne ekuguquleni ndaba, eziningi izici ezahlukene. Kungase kube nemiphumela ehlukile, imiphumela ezishisayo; ezinye izinqubo bayahamba ukuqedela, kuziwa kwamanye amakhemikhali zilingana. Ukushintsha ejenti luvame ukuhambisana ngokwandisa noma ukunciphisa degree of namachibi. Esikhathini ngezigaba imihlola chemical emiphumeleni yabo yokugcina ukuziqhakambisa umehluko qualitative ambalwa phakathi reactants kusuka imikhiqizo. Lezi zici zingaba ovelele 7 izinhlobo zamakhemikhali, kuhlanganise esikhundleni, beqhubeka ngokwezifiso isikimu: A B C A + C + B. Ukubhalwa lula bonkhe eklasini bafundza incwadzi imihlola chemical kunikela umqondo wokuthi phakathi izinto sokuqala okubizwa ngokuthi "umhlaseli "kuyizinhlayiyana substituent nakuyi-athomu reagent, ion iqembu sokusebenza. Ukusabela esikhundleni kuyisici sobuntu ayegcwele kanye hydrocarbon elimnandi.

esikhundleni ukuphendula singenzeka ngesimo kabili exchange: A B C + E C + A-B-E. Omunye zenyathi - ukufuduka, isib, ithusi, insimbi evela isixazululo zethusi sulphate: CuSO ₄ + Fe = FeSO ₄ + Cu. Njengoba "ehlasela" izinhlayiya angasebenza ama-athomu, ion noma amaqembu obusebenzayo

esikhundleni Homolytic (olukhulu, SR)

Lapho lo mshini olukhulu uqhekeko covalent electron pair okuvamile izakhi ezahlukene uzobe kulingana basakaza phakathi "izingcezwana" engqamuzaneni. Kumiswa radicals khulula. Lokhu engazinzile kuyizinhlayiyana njengoba sinjalo okuyinto eyenzeka ngenxa ukusabela okwalandela. Ngokwesibonelo, ekulungiseleleni ethane kusukela methane ukukhiqiza radicals khulula abathintekayo ekusabeleni esikhundleni: CH ₄ CH ₃ • + • H; CH ₃ • + • CH ₃ → C2H5; H • + • H → H2. Homolytic isibopho cleavage ngalo mshini okusebenza esikhundleni kuyisici sobuntu alkanes, ukusabela kuyinto umlingisi uchungechunge. Athomu methane H kungenzeka zilandelana sithathelwe indawo chlorine. Ngokufanayo ukuxubana uxhumano lokudlulisa, iodine kodwa ayikwazi ngqo esikhundleni hydrogen alkanes, fluorine iyaphendula kakhulu ngamandla nabo.

isibopho Heterolytic cleavage indlela

Lapho lo mshini ion ukugeleza esikhundleni ukusabela, ama-electron kuthiwa Ukuboshelwa kwabelwa zinhlayiya ezisanda ukudideka okukhulu. Laba bobabili yokubopha electron ubabonisa yonke indlela ukuba omunye "izingcezwana", ngokuvamile, ukuze umlingani zokuxhumana, ohlangothini elase offset ukuminyana ongathandeki engqamuzaneni polar. Ngu esikhundleni indlela esisabela ngayo zihlanganisa ukusabela kumiswa methyl utshwala CH ₃ OH. Ngo brommetane CH3Br igebe molecule uhlamvu heterolytic, izinhlayiya icala izinze. Methyl Uthola icala omuhle, futhi bromo - ezingezinhle: CH ₃ Br → CH ₃ ⁺ Br ^-; NaOH → Na ⁺ OH ^-; CH ₃ ⁺ OH ^- → CH ₃ OH; Na ⁺ Br ^- ↔ NaBr.

Electrophiles futhi nucleophiles

Izinhlayiyana angenazo electron futhi angamukela kubo, abizwa ngokuthi "electrophiles." Lawa ama-athomu carbon sasondelana halogens e haloalkanes. Nucleophiles babe okusezingeni eliphezulu electron ukuminyana, zingabantu "izisulu" yebhangqa electron ukwakha isibopho covalent. I esikhundleni ukusabela amacala ocebile negative zihlaselwa nucleophiles electrophiles, kusilela of electron. Lesi simo esiyingqayizivele sibangelwa lihlotshaniswa ukunyakaza kwama-atom noma ezinye izinhlayiya - kokushiya iqembu. Enye ezihlukahlukene esikhundleni ukusabela - ukuhlasela nucleophile electrophile. Ngezinye izikhathi kunzima ukuhlukanisa phakathi izinqubo ezimbili, okukhulunywe esikhundleni esisodwa noma olunye uhlobo, ngoba kunzima ucacise ncamashi onjani-molecule - substrate, futhi okuyinto - reagent. Ngokuvamile ezimweni ezinjalo, lezi zinto ezilandelayo ezibhekwa:

• ubunjalo iqembu kokushiya;
• the reactivity we nucleophile;
• ubunjalo kuphela;
• ingxenye alkyl isakhiwo.

esikhundleni Nucleophilic (SN)

Ngo inqubo yokusebenzisana engqamuzaneni organic has kuyanda nokwehlukana. Esikhathini zibalo of ngokwengxenye icala emihle noma emibi kuboniswa incwadi zamagama ngesiGreki. zokuxhumana nokwehlukana likhomba ubunjalo ukudabuka kwalo futhi ukuziphatha ikusasa "izingcezwana" engqamuzaneni. Ngokwesibonelo, e-athomu carbon ku iodomethane has a icala omuhle ngokwengxenye, kuba isikhungo electrophilic. It edonsela dipole emanzini, lapho umoya-mpilo likwazi ngokweqile electron. Ngo ukusabela electrophile nge nucleophile Kumiswa methanol: CH ₃ Mina + H ₂ O → CH ₃ OH + HI. nucleophilic esikhundleni ukusabela mazenzeke iqhaza noma ion omubi icala noma i-molecule kokuba khulula electron pair, okungadingi iqhaza ekwakheni isibopho zamakhemikhali. iqhaza okusebenzayo kwe iodomethane e SN _{2-ukuphendula} ngenxa nokuvuleka yayo ukuhlasela nucleophilic iodine ukuhamba.

esikhundleni Electrophilic (SE)

I-molecule organic kungenzeka isikhungo samanje nucleophilic, esibonakala by ngokweqile electron kwabantu. It ihlangana ukuntuleka amacala ezimbi reagent electrophilic. izinhlayiya ezinjalo ama-athomu kokuba khulula molecule ye esemkhathini ngezingxenye zikamagazini i-enciphile electron kwabantu. I -sodium formate carbon kokuba icala "-", is wasithukuthelela ingxenye omuhle dipole amanzi - hydrogen: CH ₃ Na + H ₂ O → CH ₄ + NaOH. Umkhiqizo okunjena, esikhundleni electrophilic - methane. Lapho ukusabela heterolytic uxhumana oppositely icala izikhungo amangqamuzana angokwemvelo obanika wahlangana ngobuhlobo ion e wezinto izinto kwamakhemikhali. Kufanele ngeke zinganakwa ukuthi ukuguquka organic compounds kuyaqabukela ephelezelwa ukwakheka la cations futhi anions.

Unimolecular nezimpendulo bimolecular

I esikhundleni nucleophilic kuyinto monomolecular (SN1). Ngalokhu indlela, umkhiqizo obalulekile ageleza hydrolysis ka zamagama organic - butyl ephakeme chloride. Isigaba sokuqala uyephuza, ihlobene dissociation okuqhubekayo ku carbonium seka futhi anion chloride. Isigaba sesibili kuyindlela yemvelo yokusabela lapho ngokushesha kwenzeka ion namanzi carbonium. I kwesibalo ukuthi bayavuma wokumelana ka Halogen ku alkane ukuthola utshwala hydroxy futhi eziyinhloko: (CH _{3) 3} C-Cl → (CH _{3) 3} C ⁺ Cl ^-; (CH _{3) 3} C ⁺ H ₂ O → (CH _{3) 3} C-OH ⁺ H +. Ukuze sesinyathelo esisodwa hydrolysis of aphansi nezamabanga aphakeme alkyl halides libhekene ekubhujisweni kanyekanye carbon ngenxa Halogen kanye kumiswa pair C-OH. Lokhu nucleophilic bimolecular esikhundleni indlela (SN2).

indlela Heterolytic wokumelana

esikhundleni indlela kuhilela ukudlulisela electron, ukudalwa izakhiwo Lesisemkhatsini. Ukusabela wabe ngokushesha kakhudlwana, kuba lula ngoba ushintsho ejwayelekile wakhe. Ngokuvamile inqubo kwenzekani e tinkhombandlela eziningana kanyekanye. Inzuzo uvamise indlela ezisetshenziswa izinhlayiya, ezidinga imali esetshenzisiwe okungenani yamandla ezikhungweni zokuphehla lasungulwa. Ngokwesibonelo, ukuba khona isibopho double kwandisa amathuba i seka Allyl CH 2 = CH-CH ₂ ^+, uma kuqhathaniswa _CH3 ⁺ ion. Isizathu itholakala ukuminyana electron ngesibopho amaningi, othinta delocalization we icala omuhle, bahlakazeka phezu kwawo wonke-molecule.

benzene esikhundleni ukuphendula

Iqembu of organic compounds, izimpawu esikhundleni electrophilic - enkundleni. Benzene indandatho - into elula sokuhlasela electrophilic. Inqubo iqala ukuxhumana yesibili nokwehlukana reagent, kanjalo ukwakha electrophile electron ifu eduze iringi benzene. Umphumela inguquko eziyinkimbinkimbi. Zenani elikhulu zokuxhumana izinhlayiya electrophilic nomunye athomu carbon okwamanje, it is bakhangwa yonke icala omubi "elimnandi eziyisithupha" electron. In the isinyathelo sesithathu senqubo electrophile nokukodwa indandatho carbon athomu Abophe pair ezivamile electron (covalent isibopho). Kodwa kulokhu, ukubhujiswa the "elimnandi eziyisithupha", okuyinto disadvantageous ngokuya nokufeza isimo amandla esitebeleni esimeme. Kukhona lomkhuba wokuthi kungenziwa ebizwa nge- "ukukhululwa kwe-proton." It is ukuzehlukanisa H ⁺ ukuze ^alulame uhlelo zokuxhumana ezinzile, lamaNazaretha ejwayelekile. izidakamizwa Side yakhiwa hydrogen seka yeringi benzene kanye anion kusukela reagent yesibili.

Izibonelo esikhundleni ukusabela yokuthakwa kwamakhemikhali organic

Ukuze alkanes ejwayelekile ikakhulukazi esikhundleni ukuphendula. Izibonelo ukusabela electrophilic futhi nucleophilic kungaholela cycloalkanes futhi lamaNazaretha. ukusabela okufanayo amangqamuzana izinto eziningi eziphilayo kukhona ngaphansi kwezimo ezivamile, kodwa ngokuvamile - futhi bafudumale in khona catalysts. Ngu izinqubo ezivamile futhi wafundelwa kahle zihlanganisa electrophilic esikhundleni elimnandi. Ukusabela ebaluleke kakhulu kulolu hlobo:

1. Nitration ka-benzene nge nitric acid ebukhoneni H ₂ SO ₄ - lulandela uhlelo: C ₆ H ₆ → C ₆ H ₅ ayinaso _2.
2. I halogenation okhanda amanye amathuba benzene, ikakhulukazi chlorination, yi-equation: C ₆ H ₆ + Cl ₂ → C ₆ H ₅ Cl + HCl.
3. sulfonation elimnandi we-benzene ukuqhutshwa nge "kabi" sulfuric acid, benzenesulfonic acid akhiwa.
4. Alkylation - esikhundleni athomu ye-hydrogen kusukela esiyingini benzene ukuze alkyl.
5. Acylation - kumiswa ketones.
6. Formylation - ukususa hydrogen isigcawu Cho kanye kumiswa aldehydes.

Ngu esikhundleni indlela esisabela ngayo zihlanganisa ukusabela alkanes futhi cycloalkanes, lapho halogens ukuhlasela etholakalayo C-H isibopho. Derivatization lingaphathelaniswa ne esikhundleni esisodwa, ezimbili noma zonke ukuzulazula kwama-athomu ye-hydrogen e hydrocarbon ayegcwele kanye cycloparaffins. Abaningi galogenoalkanov ka ongaphakeme isisindo yamangqamuzana asetshenziswa ekukhiqizeni ngaphezulu izinto eziyinkimbinkimbi okuqondene amakilasi ezahlukene. I impumelelo izuzwe ekuhloleni izindlela esikhundleni ukusabela, wanika yisisusa esinamandla ekuthuthukiseni syntheses ngesisekelo alkanes, Cyclo-esiteji hydrocarbon halogenated.