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30 Νοε 2012 · For our purposes, “ strong ” nucleophiles/bases are negatively charged and “ weak” nucleophiles/bases are neutral. A good rule of thumb is to expect SN2/E2 with “ strong ‘ (i.e. negatively charged) nucleophiles/bases and expect SN1/E1 with neutral nucleophiles/bases.
- The Solvent
I heard the explanation is that OH- is a good nucleophile...
- The Solvent
Bimolecular nucleophilic substitution (S N 2) reactions are concerted, meaning they are a one step process. This means that the process whereby the nucleophile attacks and the leaving group leaves is simultaneous.
16 Δεκ 2021 · The general guideline for solvents regarding nucleophilic substitution reaction is: S N 1 reactions are favored by polar protic solvents (H 2 O, ROH etc), and usually are solvolysis reactions. S N 2 reactions are favored by polar aprotic solvents (acetone, DMSO, DMF etc).
24 Μαΐ 2021 · The rate of an S N 2 reaction is significantly influenced by the solvent in which the reaction takes place. The use of protic solvents (those, such as water or alcohols, with hydrogen-bond donating capability) decreases the power of the nucleophile through strong solvation.
Some general guidelines for understanding S N 2 reactions include: (a) stronger bases are better nucleophiles, unless an E2 pathway is accessible which benefits more from a strong base than S N 2; (b) leaving groups with a weak bond to the substrate present enhanced reactivity (C−I ≫ C−F); (c) increasingly electropositive central atoms ...
4 Δεκ 2012 · I heard the explanation is that OH- is a good nucleophile for an SN2 reaction, and when there’s alcohol and KOH the OH- can deprotonate the alcohol to get alkoxide ion, which is a stronger base than a nucleophile, so takes a proton for an E2 reaction.
31 Αυγ 2020 · A Lewis base acting as a strong nucleophile is needed for S N 2 reactions, whereas a Lewis base acting as a strong protophile (i.e., base) is required for E2 reactions. A complicating factor is, however, the fact that a good nucleophile is often a strong protophile.
