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Sodium methoxide is prepared by treating methanol with sodium: 2 Na + 2 CH 3 OH → 2 CH 3 ONa + H 2. The reaction is so exothermic that ignition is possible. The resulting solution, which is colorless, is often used as a source of sodium methoxide, but the pure material can be isolated by evaporation followed by heating to remove residual methanol.
A hydroxide ion acting as a nucleophile in an S N 2 reaction, converting a haloalkane into an alcohol. In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they ...
Other strong non-nucleophilic bases are sodium hydride and potassium hydride. These compounds are dense, salt-like materials that are insoluble and operate by surface reactions. Some reagents are of high basicity (pK a of conjugate acid around 17) but of modest but not negligible nucleophilicity.
An alcohol is not a particularly strong nucleophile and, when present, more powerful nucleophiles like amines will react with the above-mentioned reagents in preference to the alcohol. [ 5 ] Alcohol deprotection
A nucleophilic aromatic substitution (S N Ar) is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring. Aromatic rings are usually nucleophilic, but some aromatic compounds do undergo nucleophilic substitution.
Like the aldol addition, the Michael reaction may proceed via an enol, silyl enol ether in the Mukaiyama–Michael addition, or more usually, enolate nucleophile. In the latter case, the stabilized carbonyl compound is deprotonated with a strong base (hard enolization) or with a Lewis acid and a weak base (soft
The aldol reaction has one underlying mechanism: a carbanion-like nucleophile attacks a carbonyl center. [ 12 ] If the base is of only moderate strength such as hydroxide ion or an alkoxide , the aldol reaction occurs via nucleophilic attack by the resonance-stabilized enolate on the carbonyl group of another molecule.
If the conditions are particularly harsh (e.g.: NaOMe/MeOH/reflux), condensation may occur. However if an Aldol addition is desired, this can usually be avoided with mild reagents and low temperatures (e.g., LDA (a strong base), THF, −78 °C). Although aldol addition usually proceeds to near completion under irreversible conditions, the ...