Usoro Mmeghachi omume SN1 na SN2
Mmeghachi omume nnọchi Nucleophilic bụ ụdị mmeghachi omume kemịkalụ a na-ahụkarị na kemịkalụ organic. Ha gụnyere nnọchi otu otu ọrụ na nke ọzọ n'ime otu molekul ahụ. Usoro abụọ bụ isi na-achịkwa mmeghachi omume nnọchi nucleophilic bụ SN1 (mmeghachi omume nnọchi nucleophilic unimolecular) na SN2 (mmeghachi omume nnọchi nucleophilic bimolecular). Ịghọta usoro dị iche iche ndị a dị oke mkpa n'ọmụmụ ihe gbasara kemịkalụ organic, ebe ọ bụ na usoro ọ bụla nwere njirimara, ọnọdụ, na mmepụta ngwaahịa dị iche iche.
Usoro SN1
SN1 na-anọchite anya "Unimolecular Nucleophilic Replacement." Usoro a nwere usoro abụọ, ya bụ nhazi nke carbocation dị ka nzọụkwụ mbụ, wee soro mwakpo nucleophilic na carbocation.
Nkebi nke 1: Nhazi Carbocation
Nzọụkwụ mbụ n'ime usoro SN1 bụ nkewa nke otu ndị na-apụ na molekul nne na nna iji mepụta carbocation. Otu ndị na-apụ dị mma bụ nke a na-ewepụ ngwa ngwa, dị ka halide (Cl^-, Br^-, I^-) ma ọ bụ tosylate. Usoro a abụghị otu molekul n'ihi na ọ gụnyere naanị otu molekul na usoro ikpebi ọnụego, ya bụ ihe mejupụtara nne na nna n'onwe ya.
\[
RL \akara aka nri R^+ + L^-
\]
N'ebe a, RL bụ molekul nne, R^+ bụ carbohydrate, na L^- bụ otu na-apụ apụ.
Nzọụkwụ nke 2: Mwakpo Nuklia
Na nzọụkwụ nke abụọ, nucleophile na-awakpo carbocation e guzobere iji mepụta ngwaahịa nnọchi.
\[
R^+ + Nuc^- \akara aka nri R-Nuc
\]
N'ime mmeghachi omume SN1, ihe ịga nke ọma nke mmeghachi omume ahụ dabere nke ukwuu n'otú carbohydrate ahụ si dịgide. Ya mere, mmeghachi omume SN1 na-emekarị na carbocations tertiary kwụsiri ike karịa na carbocations praịmarị ma ọ bụ nke abụọ.
Àgwà nke mmeghachi omume SN1
1. Nkwụsi ike nke Carbocation: Ka carbohydrate ahụ na-adịkwu mma, otú ahụ ka mmeghachi omume SN1 na-adị mfe. Ya mere, SN1 na-adịkarị na carbons nke atọ.
2. Stereochemistry: Mmeghachi omume SN1 na-emepụtakarị ngwakọta agbụrụ n'ihi na carbonation bụ planar na nucleophile nwere ike ịwakpo site n'akụkụ abụọ ahụ.
3. Ihe mgbaze: Ihe mgbaze polar protic dị ka mmiri na mmanya na-akwado mmeghachi omume SN1 n'ihi nkwụsi ike nke ion ndị e guzobere.
Usoro SN2
SN2 na-anọchite anya "Nnọchianya Nucleophilic Bimolecular." N'usoro a, nucleophile na-awakpo carbon ejikọtara na otu ndị na-apụ apụ n'otu oge ahụ na-ewepụ otu ndị na-apụ apụ.
Mwakpo Nuklia na Mwepụ nke Otu
Mmeghachi omume SN2 na-eme n'otu nzọụkwụ (usoro a na-akpọ concerted mechanism), ebe nucleophile na-awakpo carbon nke dị n'akụkụ azụ nke otu ndị na-apụ apụ, ebe a na-ahapụ otu ndị na-apụ apụ.
\[
Nuc^- + RL \nriaka R-Nuc + L^-
\]
Usoro a bụ bimolecular n'ihi na ọ gụnyere molekul abụọ n'ime usoro ikpebi ọnụego, ya bụ nucleophile na ihe mejupụtara nne na nna.
Àgwà nke mmeghachi omume SN2
1. Mgbochi Steric: Ebe ọ bụ na nucleophile ga-awakpo site n'azụ, mmeghachi omume SN2 na-eme ngwa ngwa na praịmarị na nke abụọ carbons. A na-egbochikarị kabọn atọ nke atọ ka a ghara ịwakpo ha na usoro a.
2. Stereochemistry: Mmeghachi omume SN2 na-emepụta mgbanwe nhazi (Walden inversion) na etiti stereogenic, nke mere na ihe ndị na-arụ ọrụ anya nke na-agafe mmeghachi omume SN2 ga-emepụta ngwaahịa nwere nhazi dị iche.
3. Ihe Nchedo na Ihe Mgbaze: Ihe mgbaze aprotic nke Polar dị ka acetonitrile, dimethyl sulfoxide (DMSO), ma ọ bụ acetone na-akwado usoro SN2 n'ihi na ha anaghị eme ka nucleophile kwụsie ike nke ukwuu site na mgbaze.
Ntụnyere n'etiti SN1 na SN2
Mgbe ị na-ahọrọ n'etiti usoro SN1 na SN2, a ghaghị ịtụle ọtụtụ ihe:
1. Nhazi nke ihe ndị dị n'okpuru ala:
– SN1: A na-ahọrọ ya maka ihe ndị nwere carbocation kwụsiri ike (tertiary > secondary > praịmarị).
– SN2: A na-ahọrọ ya maka ihe ndị nwere obere ihe mgbochi steric (isi > nke abụọ > nke atọ).
2. Onye Nuklia:
– SN1: Ọ naghị adabere na ike nke nucleophile, n'ihi na usoro ikpebi ọnụego anaghị agụnye nucleophile.
– SN2: Chọrọ nucleophile siri ike n'ihi na mwakpo nucleophilic bụ nzọụkwụ na-ekpebi ọnụego.
3. Ịhapụ Otu:
– Usoro abụọ a chọrọ ezigbo otu ndị na-apụ apụ nke nwere ike ịpụ n'òtù nne na nna ngwa ngwa.
4. Ihe mgbaze:
– SN1: Ihe mgbaze polar protic nke na-eme ka ion kwụsie ike.
– SN2: Ihe mgbaze polar nke na-eme ka ion kwụsie ike mana ọ naghị eme ka nucleophiles kwụsie ike.
5. Stereokemistri:
– SN1: Ngwakọta agbụrụ n'ihi na nucleophile nwere ike ịwakpo site n'akụkụ abụọ nke carbocation.
– SN2: Mgbanwe nhazi n'ihi mwakpo nucleophilic site n'akụkụ dị n'akụkụ otu na-apụ apụ.
Ihe atụ nke mmeghachi omume SN1 na SN2
Ihe atụ nke mmeghachi omume SN1
Mmeghachi omume nke mmiri mmiri nke Tert-Butyl alkyl halide na mmiri:
\[
\ederede{(CH}_3\ederede{)}_3\ederede{C-Br} + H_2O \rightarrow \ederede{(CH}_3\ederede{)}_3\ederede{C-OH} + HBr
\]
N'ime mmeghachi omume a, tert-butyl bromide na-emepụta tert-butyl carbocation mgbe otu bromide ahụ kewara, wee soro mwakpo nucleophilic site na mmiri.
Ihe atụ nke mmeghachi omume SN2
Mmeghachi omume nke methyl bromide na ion hydroxide:
\[
\ederede{CH}_3\ederede{Br} + OH^- \rightarrow \ederede{CH}_3\ederede{OH} + Br^-
\]
N'ebe a, ion hydroxide na-awakpo azụ nke methyl carbon ejikọtara na otu bromide n'otu oge na mwepụta nke otu bromide, na-emepụta methanol.
Mmechi
Mmeghachi omume SN1 na SN2 bụ ụzọ abụọ dị mkpa isi mee ka mmeghachi omume nukliọfik dochie anya, yana ọdịiche dị mkpa n'ụdị ọrụ ha. SN1 chọrọ ka e mepụta carbocation ma na-emekarị ya na nnukwu ihe ndị nwere alaka karịa, ebe SN2 na-aga n'otu nzọụkwụ ebe nukliọfik na-awakpo njikọ carbon nke dị na otu ndị na-apụ apụ ozugbo, na-ahọrọ obere ihe ndị na-adịghị na alaka. Nghọta zuru oke nke ọnọdụ ndị na-akwado usoro ọ bụla na ngwaahịa ndị sitere na ya dị oke mkpa na mmepụta kemịkalụ organic.
