Question

Question: Identify the stronger nucleophile in each pair

a.NH₃ NH₂ ${\mathrm{NH}}_3,{\mathrm{NH}}_2$

b.CH₃ NH₂ ,CH₃ OH ${\mathrm{CH}}_3{\mathrm{NH}}_2,{\mathrm{CH}}_3\mathrm{OH}$

c.CH₃CO₂^- ,CH₃CH₂O^- ${\mathrm{CH}}_3{{\mathrm{CO}}_2}^{-},{\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{O}}^{-}$

Short answer

Answer

a. NH₂^-is the stronger nucleophile in this pair.

b. CH₃NH₂is the stronger nucleophile in this pair.

c.CH₃CH₂O^-a stronger nucleophile in this pair.

Step-by-step solution

Nucleophile

Nucleophiles and bases possess identical structures. They differ in terms of the species they attack.

Nucleophiles strike electron-deficient atoms like carbon, while bases strike protons.

Conditions to identify the stronger nucleophile in each pair

When two nucleophiles possess the same attacking atom, the stronger base is considered the stronger nucleophile. Nucleophiles possessing a negative charge are powerful than their conjugate acids.

Across a row in a periodic table, nucleophilicity decreases when species possess similar charges.

Identification of stronger nucleophile in each pair

a. The conjugate acid of NH₂^- is NH₃ . A nucleophile containing a negative charge is stronger than the conjugate acid. Hence, NH₂^- is a stronger nucleophile than NH₃ .

b. When moving across a row in a periodic table, nucleophilicity decreases for species comprising similar charges. Hence, CH₃ NH₂is a stronger nucleophile than CH₃ OH.

c. The conjugate acid of CH₃ CO₂^- is CH₃ COOH and that of CH₃CH₂O^-of is CH₃CH₂OH .The acidic strength of CH₃ COOH is more than CH₃CH₂OH .So, CH₃ COOH forms a conjugate base with low basicity.

Hence,CH₃CH₂O^- is a powerful nucleophile as the conjugate acid is a weak acid.