(2) The “strength” of a nucleophile is also related to its size. It is pretty safe to assume that any anion (atom or molecule with negative formal charge) is a strong nucleophile. Why? Because it ionizes leaving $Na^+$, a spectator ion, and $CN^-$ cyanide anion, a strong nucleophile. When dissolved in acetone it is a strong nucleophile. Example: $NaCN$ is a metal ($Na$) bonded to a non-metal $C$). (1) Metal bonded to a non-metal is an ionic bond therefore it will ionize in solution. Bulky substrates (like tertiary) tend towards E2 non-bulky (like primary) tend towards SN2.Ī bulky base is not a good nucleophile since it cannot squeeze close into the carbon, so it tends towards E2.Ī discussion of the above points: Chad's Prep, 7.7 (~4 min).Ī discussion of the “anti-periplanar” requirement for E2 reactions: Chad's Prep, 7.5 E2 Reactions (~4:50 min) These are $OH^-$ or substance with a negative charge on an oxygen ($RO^-$). If you have a negative charge on anything other than oxygen it is probably just a strong nucleophile/weak base → SN2.Ī strong nucleophile/strong base results in SN2-E2 reactions (that compete). These are nucleophiles that have a negative charge (except on oxygen) like the halides or contain sulfur, nitrogen or phosphorus. If you have a strong nucleophile that is a weak base, you are probably dealing with SN2 only. If you have weak nucelophile/base you're probably dealing with SN1 & E1 and you'll get a mixture of the two. to leave creating a carbocation in 1st (slow) step then the solvent (weak base) strips off a β hydrogen forming a double bond any substrate except 1° (too unstable) in one step any substrate (unhindered or not) Strong base deprotonates substrate forming pi bond and kicking off L.G.
to leave creating a carbocation in 1st (slow) step then the weak nucleophile attacks the carbon relatively hindered substrate Strong nucleophile does backside attack on substrate in one step relatively unhindered substrate Here is a summary chart in a different format that you might find helpful. Usu only moves to adjacent carbon that is more substituted *aprotic is better but does not matter (DNM) SN1: solvent & nuc: usually the same (“solvolysis”) SN2, E2 - “stronger with 2 arms” SN1: carbocation stability controls (steric hindrance prevents backside attack) SN2: backside attack E1 primary OK (not forming a carbocation) ***Shortlister retains the exclusive right to grant or deny access to any party to ensure the privacy of the vendors in our system.SN1: step 3 $O$ has only one lone pair & has +1 formal charge, quite acidic (similar to $H_3O^+$), donates $H$ to another solvent molecule You can email Tom Ciccotti at to learn more about Shortlister Select. If you are a consultant, Shortlister offers a specialized product for consultants, called Shortlister Select. Examples of individuals that would not be granted access include, but are not limited to: vendors, students, practitioners, researchers, other non-employers or anyone that is unwilling to identify themselves will not pass our vetting criteria.
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