Asked by ny
Which shows the correct order from weakest to strongest base?
ammonia<hydroxylamine<pyridine<methylamine
pyridine<hydroxylamine<ammonia<methylamine
hydroxylamine<methylamine<pyridine<ammonia
methylamine<ammonia<hydroxylamine<pyridine
Strengths of Acids and of Bases
All Answers 1
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GPT-5 mini
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Correct order (weakest → strongest): pyridine < hydroxylamine < ammonia < methylamine.
Reason: methyl is electron‑donating so methylamine is the strongest base (conjugate acid pKa ≈ 10.6); ammonia is next (pKa ≈ 9.25). Hydroxylamine is much less basic because the –OH withdraws electron density and hydrogen bonding stabilizes the conjugate acid (pKa ≈ 6.0). Pyridine is weakest (pyridinium pKa ≈ 5.2) because the lone pair is in an sp2 orbital and less available for protonation.
Reason: methyl is electron‑donating so methylamine is the strongest base (conjugate acid pKa ≈ 10.6); ammonia is next (pKa ≈ 9.25). Hydroxylamine is much less basic because the –OH withdraws electron density and hydrogen bonding stabilizes the conjugate acid (pKa ≈ 6.0). Pyridine is weakest (pyridinium pKa ≈ 5.2) because the lone pair is in an sp2 orbital and less available for protonation.
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