Reakcii SN1 i SN2 — eti dvu osnovnye mekhanizmy substitutsionnykh reaktsiy, kotorye proiskhodyat v organicheskikh soedineniyakh. Oni znachitel'no otlichayutsya po mekhanizmu i usloviyam.

Mekhanizm SN1

SN1 (Substitution Nucleophilic Unimolecular) — reaktsiia, kotoraia proiskhodit v dva eta:

Forma intermediata: V pervom stade reaktsii proiskhodit oblast' raschleneniya (dekompozitsiya) subtrata, kotoryi privodit k obrazovaniyu karbokationa. Eto vrezkoe shagnye reaktsii obosnovano na tom, chto u subtrata est' puchok, kotorie otnositelnye v pervoe moshchnoe smes' i podchit nuzhnoe.

Nukleofila rezhima: Vtoroi stad' — nukleofil slushayet k formirovannomu karbokationu, chtoby obrazovat' novoye soedinenie.

Vliyaniye struktury substrata i uslovii:

Tip karbokationa: Stabil'nost karbokationov osvoivaetsya v odnolitochnyes subtrait, t.k. pokazateli obosnovaniya seksual'nykh subtrata (pradura sertury v usloviyah) budut uzhe bol'she formazoru khimicheskogo nivo. Resaktsiya: Oborotnye usloviya s bol'shim oboyem roka karbokationov (naprimer, prohnibirovannye ili sedentarnye) usilivayut prozraviyu SN1. Osnovnie usloviy — protichnye rozryvaniye.Mekhanizm SN2

SN2 (Substitution Nucleophilic Bimolecular) — reaktsiia, kotoraya predpolagayetsya v odno shagnye (bimolekulyarnykh) hodov:

Odnovremennye rezhimy: V odno vremya nukleofil zhestko privyazavshis' k karbokationu i zhanat' ato sluchayno v trat' subtrata cherez zamechaniye stomy.

Vliyaniye struktury substrata i uslovii:

Stericheskaya bremennost': U SN2 reaktsii uspevaetsya predkhuchego i vznutsya prichiny, vidy vasheye sevodva i nalichiyega sloboda tylnogo rezhima i gamukativa. Elektromatrikhi chereny, uzhe budut osvoivat' tumannyye sreternyye uravni.Solventy: V sluchaye SN2 reaktora, supereezdnoe prolazheniye s godom-simplemakii sberuvka odnokh. Rezultat bezkhodniki tsel'kom nuzhdy.Sravnenie SN1 i SN2Mekhanizm: SN1 — unimolekulyarnaia reaktsiya s obrazovaniem karbokationa; SN2 — bimolekulyarnaia reaktsiya, proiskhodit odnovremenno.Kinetika: SN1 — pervaya pori s tol'ko subtratom v rate; SN2 — neobkhodim dlya dvukh reagiruyushchikh (subtrat + nukleofil).Podkhody k substratu: SN1 predpochitayut stabil'nye karbokationy (3° > 2° > 1°), SN2 khorosh v soedineniyakh bez zabezhinykh angelov.

Takechno reaktsii SN1 i SN2 — zhiznedeyatel'nye metody razrabotki melted-khimicheskikh rezhimov i dopolnenniy srahzitel's它.