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Chapter

CHE 118A Chapter Notes -Tert-Butyllithium, Acetylide, Azide


Department
Chemistry
Course Code
CHE 118A
Professor
Vahid Eskandari

Page:
of 2
Strong Nucleophiles
Usually anions with a full negative charge (easily recognizable by the presence of sodium, lithium or
potassium counterions)
Participate in SN2-type substitutions
Examples:
NaOCH3 (any NaOR), LiCH3 (any RLi), NaOH or KOH, NaCN or KCN, NaCCR (acetylide anion),
NaNH2, NaNHR, NaNR2, NaI, LiBr, KI, NaN3
Weak Nucleophiles
Typically neutral molecules
Participate in SN1-type substitutions
Examples:
H2O, ROH, H2S, RSH
Strong Bases
Usually anions with a full negative charge (easily recognizable by the presence of sodium, lithium or
potassium counterions)
Participate in E2-type eliminations
May overlap with strong nucleophile list (causing mixtures of both substitutions and eliminations to be
produced)
Halides and the azide anion are nucleophilic but not basic only strong nucleophiles that are not also
strong bases.
Examples:
NaOCH3 (any NaOR), LiCH3 (any RLi), NaOH or KOH, NaCN or KCN, NaCCR (acetylide anion),
NaNH2, NaNHR, NaNR2
Weak Bases
Typically neutral molecules
Participate in E1-type eliminations
Can occur concurrently with SN1 reactions since both occur under similar conditions (type of halide,
carbocation intermediate, neutral nucleophile/base)
Examples:
H2O, ROH, H2S, RSH
Strong, Non-Nucleophilic Bases (SNNB)
Usually anions that are very sterically hindered, preventing them from attacking as nucleophiles (thus the
phrase “non-nucleophilic”)
Participate in E2 ONLY
Examples:
Tert-butyl Lithium : tBuLi (also written as (CH3)3CLi)
PotassiumTert-butoxide : KOtBu (also written as (KOC(CH3)3)
Lithium Diisopropylamide : LDA (acronym) (also written as LiN(CH(CH3)2)2)