What are Amines and Amides?
Amines (RNH₂, R₂NH, R₃N) are organic bases containing nitrogen bonded to carbon. Amides (RCONH₂, RCONHR, RCONR₂) have nitrogen bonded to a carbonyl carbon. While amines are bases, amides are weakly basic or acidic due to resonance.
Amines are organic derivatives of ammonia with the N bonded to carbon(s). Amides contain the C(=O)-N group and are stabilized by resonance. Amines are basic and nucleophilic; amides are weakly basic and more stable.
- •RNH₂ (primary)
- •R₂NH (secondary)
- •R₃N (tertiary)
- •Basic, nucleophilic
- •RCONH₂ (primary)
- •RCONHR (secondary)
- •RCONR₂ (tertiary)
- •Weakly basic, resonance-stabilized
Step-by-step worked examples
Classify CH₃NH₂ as a primary, secondary, or tertiary amine.
Look at the nitrogen and count carbon atoms attached CH₃NH₂: only 1 carbon bonded to N This is a PRIMARY (1°) amine Primary amines have the most basic lone pair (most reactive)
How is acetamide (CH₃CONH₂) formed from acetic acid?
Start with acetic acid CH₃COOH Convert to acyl halide: CH₃COCl React acyl halide with ammonia: CH₃COCl + NH₃ → CH₃CONH₂ + HCl Amides are easily formed from acyl halides and amines/ammonia
Why are amides less basic than amines?
In amides, the N lone pair resonates with the C=O Resonance delocalizes the N lone pair (forms partial C-N double bond) The lone pair is less available for protonation Result: amides are very weak bases (pKb >> 9)
Flashcards
Quick quiz
Q1.(CH₃)₂NH is what class of amine?
Q2.Amides are formed by reacting…
Q3.Which is more basic, an amine or an amide?
Q4.The N in an amide is stabilized by…
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Common mistakes
Amines and amides have the same reactivity. — Correct: Amines are much more reactive and basic; amides are stabilized by resonance.
All amides are weak acids. — Correct: Primary and secondary amides are weakly acidic (on N-H); tertiary are not acidic.
Amides have a true C=N double bond. — Correct: Due to resonance, amides have partial C-N double bond character (~40%).
Tertiary amines cannot form amides. — Correct: Tertiary amines can form amides: R₃N + RCOCl → R₃N⁺-COR + Cl⁻, but they form salts with acyl halides.
FAQ
What is the main difference between amines and amides?
Amines: N bonded to C (C-N). Amides: N bonded to carbonyl carbon (C(=O)-N).
How do you classify amines?
Primary: RNH₂ (1 carbon). Secondary: R₂NH (2 carbons). Tertiary: R₃N (3 carbons).
Why are amides less basic than amines?
Resonance delocalizes the N lone pair into the C=O, reducing its availability for protonation.
How are amides useful in chemistry?
Amides are stable, found in proteins, and widely used in synthesis and pharmaceuticals.