Qhov Tseem Ceeb Qhov txawv - SN2 vs E2 Cov Lus Teb
Qhov sib txawv tseem ceeb ntawm SN2 thiab E2 cov tshuaj tiv thaiv yog tias SN2 cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv nucleophilic hloov pauv thaum E2 cov tshuaj tiv thaiv yog tshem tawm cov tshuaj tiv thaiv. Cov tshuaj tiv thaiv no tseem ceeb heev hauv cov organic chemistry vim tias qhov tsim ntawm cov organic sib txawv tau piav qhia los ntawm cov tshuaj tiv thaiv no.
Muaj ob hom kev hloov pauv nucleophilic muaj npe hu ua SN1 cov tshuaj tiv thaiv thiab SN2 cov tshuaj tiv thaiv uas sib txawv ntawm ib leeg raws li tus lej ntawm cov kauj ruam hauv txhua lub tswv yim. Txawm li cas los xij, ob qho tib si no suav nrog kev hloov pauv ntawm pab pawg ua haujlwm hauv cov organic sib xyaw nrog nucleophile. Muaj ob hom kev tshem tawm cov tshuaj tiv thaiv npe hu ua E1 thiab E2 cov tshuaj tiv thaiv. Cov tshuaj tiv thaiv no muab cov txheej txheem ntawm kev tshem tawm cov pab pawg ua haujlwm los ntawm cov organic compound.
SN2 Cov Lus Teb yog dab tsi?
SN2 cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv nucleophilic hloov pauv uas yog bimolecular. Cov tshuaj tiv thaiv SN2 yog cov tshuaj tiv thaiv ib kauj ruam. Qhov no txhais tau tias kev sib tsoo thiab kev tsim cov nyiaj tau los tshwm sim hauv tib kauj ruam. Cov tshuaj tiv thaiv yog bimolecular vim tias muaj ob lub molecules koom nrog hauv kev txiav txim siab theem ntawm SN2 cov tshuaj tiv thaiv.
Qhov kev cuam tshuam SN2 tshwm sim hauv aliphatic sp3 carbon cov chaw nrog cov pab pawg ruaj khov uas txuas nrog lub chaw carbon no. Cov pab pawg tawm no yog electronegative ntau dua li carbon. Feem ntau, cov pab pawg tawm yog halide atom vim halides yog cov electronegative thiab ruaj khov.
SN2 cov tshuaj tiv thaiv tshwm sim nyob rau hauv thawj thiab theem nrab hloov cov pa roj carbon atoms vim steric hindrance tiv thaiv cov qauv tertiary los ntawm SN2 mechanism. Yog hais tias muaj cov pawg loj nyob ib ncig ntawm cov pa roj carbon monoxide (uas ua rau muaj kev cuam tshuam tsis zoo), ces cov carbocation nruab nrab yuav raug tsim. Qhov no ua rau SN1 cov tshuaj tiv thaiv tsis yog SN2 cov tshuaj tiv thaiv.
Daim duab 01: SN2 Reaction Mechanism
Tus nqi ntawm SN2 cov tshuaj tiv thaiv nyob ntawm ntau yam; nucleophilic zog txiav txim siab tus nqi ntawm cov tshuaj tiv thaiv vim steric hindrance cuam tshuam rau lub zog nucleophilic. Cov kuab tshuaj siv hauv cov tshuaj tiv thaiv kuj cuam tshuam rau cov tshuaj tiv thaiv tus nqi; Polar aprotic cov kuab tshuaj yog nyiam rau SN2 cov tshuaj tiv thaiv. Yog tias pab pawg tawm mus ruaj khov heev, nws kuj cuam tshuam cov tshuaj tiv thaiv ntawm SN2.
E2 Cov Lus Teb yog dab tsi?
E2 cov tshuaj tiv thaiv yog tshem tawm cov tshuaj tiv thaiv hauv cov tshuaj lom neeg, uas yog cov tshuaj tiv thaiv bimolecular. Cov tshuaj tiv thaiv no hu ua bimolecular cov tshuaj tiv thaiv vim hais tias tus nqi-txiav cov kauj ruam ntawm cov tshuaj tiv thaiv muaj ob reactant molecules. Txawm li cas los xij, cov tshuaj tiv thaiv E2 yog cov tshuaj tiv thaiv ib kauj ruam. Qhov no txhais tau tias kev sib tsoo thiab kev sib koom ua ke tshwm sim hauv tib kauj ruam. Hauv qhov sib piv, E1 cov tshuaj tiv thaiv yog ob-kauj ruam.
Muaj ib lub xeev hloov pauv hauv E2 cov tshuaj tiv thaiv. Nyob rau hauv cov kev tshwm sim no, ib pab pawg neeg ua hauj lwm los yog ib qho kev hloov pauv tau raug tshem tawm los ntawm cov organic compound thaum tsim ob daim ntawv cog lus. Yog li, E2 cov tshuaj tiv thaiv ua rau unsaturation ntawm saturated chemical bonds. Hom tshuaj tiv thaiv no feem ntau pom muaj nyob hauv alkyl halides. Yeej, thawj alkyl halides nrog rau qee qhov thib ob halides tau txais E2 cov tshuaj tiv thaiv.
E2 cov tshuaj tiv thaiv tshwm sim nyob rau hauv lub xub ntiag ntawm lub hauv paus muaj zog. Tom qab ntawd tus nqi-txhais kauj ruam ntawm E2 cov tshuaj tiv thaiv suav nrog ob qho tib si substrate (pib organic compound) thiab lub hauv paus ua reactants (qhov no ua rau nws cov tshuaj tiv thaiv bimolecular).
Daim duab 02: E2 Kev Sib Tham Mechanism
Lub ntsiab tseem ceeb uas cuam tshuam rau cov tshuaj tiv thaiv ntawm E2 cov tshuaj tiv thaiv yog lub zog ntawm lub hauv paus (lub zog ntau dua ntawm lub hauv paus, siab dua cov tshuaj tiv thaiv), hom hnyav (polar protic cov kuab tshuaj yog nyiam), kev ruaj ntseg ntawm kev tawm pab pawg (siab dua qhov ruaj khov ntawm kev tawm hauv pawg, siab dua cov tshuaj tiv thaiv), thiab lwm yam.
Dab tsi yog qhov zoo sib xws ntawm SN2 thiab E2 Kev Pom Zoo?
- Ob leeg SN2 thiab E2 Cov Lus Teb yog cov tshuaj tiv thaiv bimolecular.
- Ob qho kev tshwm sim yog ib kauj ruam kev tshwm sim.
- Ob qhov kev cuam tshuam muaj nyob hauv thawj thiab theem nrab cov qauv ntawm cov organic tebchaw.
Qhov txawv ntawm SN2 thiab E2 Cov Lus Teb yog dab tsi?
SN2 vs E2 Reactions |
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| SN2 cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv nucleophilic hloov pauv uas yog bimolecular. | E2 cov tshuaj tiv thaiv yog tshem tawm cov tshuaj tiv thaiv hauv cov tshuaj lom neeg uas yog cov tshuaj bimolecular. |
| Nature | |
| SN2 cov tshuaj tiv thaiv yog kev hloov pauv. | E2 cov tshuaj tiv thaiv yog kev tshem tawm cov tshuaj tiv thaiv. |
| Nucleophile | |
| SN2 cov tshuaj tiv thaiv xav tau nucleophile. | E2 cov tshuaj tiv thaiv tsis tas yuav muaj nucleophile. |
| Base | |
| SN2 cov tshuaj tiv thaiv tsis tas yuav muaj lub hauv paus tseem ceeb. | E2 cov tshuaj tiv thaiv yuav tsum muaj lub hauv paus muaj zog. |
| Solvent Type | |
| SN2 cov tshuaj tiv thaiv nyiam polar aprotic cov kuab tshuaj. | E2 cov tshuaj tiv thaiv nyiam polar protic kuab tshuaj. |
| Yam cuam tshuam rau qhov tshwm sim | |
| Tus SN2 cov tshuaj tiv thaiv yog txiav txim siab los ntawm lub zog nucleophilic, hom hnyav, ruaj khov ntawm pawg tawm, thiab lwm yam. | Cov tshuaj tiv thaiv E2 yog txiav txim siab los ntawm lub zog ntawm lub hauv paus, hom hnyav, ruaj khov ntawm pawg tawm, thiab lwm yam. |
Summary – SN2 vs E2 Reactions
SN2 cov tshuaj tiv thaiv thiab E2 cov tshuaj tiv thaiv muaj ntau heev hauv cov organic chemistry. SN2 cov tshuaj tiv thaiv yog ib kauj ruam, bimolecular, nucleophilic hloov pauv. E2 cov tshuaj tiv thaiv yog ib kauj ruam, bimolecular, tshem tawm cov tshuaj tiv thaiv. Qhov txawv ntawm SN2 thiab E2 cov tshuaj tiv thaiv yog tias SN2 cov tshuaj tiv thaiv yog cov tshuaj tiv thaiv nucleophilic hloov pauv thaum E2 cov tshuaj tiv thaiv yog tshem tawm cov tshuaj tiv thaiv.
