Chemistry 2e · Organic Chemistry
Amines and Amides
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Amines are organic derivatives of ammonia in which one or more hydrogens are replaced by carbon groups (R-NH2, R2NH, or R3N), while amides are compounds with a carbonyl group bonded to a nitrogen (R-CO-NH2 and relatives). The two families look related because both contain nitrogen, but their chemistry is nearly opposite: amines are weak bases that smell fishy and readily grab protons, whereas amides are essentially nonbasic because the nitrogen's lone pair A pair of valence electrons not involved in bonding. Full entry → is pulled into the carbonyl group. This topic covers how to recognize, name, and classify amines, how amides form from acids and amines, and why proteins and many drugs depend on this chemistry.
Why this matters
Nitrogen chemistry runs through biology and medicine. Amines appear in adrenaline, nicotine, caffeine, and many pain relievers, and their basicity lets pharmacists convert them into water-soluble salts for injection. Amides are the links (peptide bonds) that hold amino acids together in every protein, and they form the backbone of nylon, acetaminophen, and many antibiotics. Understanding the amine An ammonia derivative with one or more carbon groups on nitrogen, R-NH2 to R3N. Full entry →–amide A compound with a carbonyl carbon bonded to nitrogen, R-CO-NH2. Full entry → difference explains why some nitrogen drugs can be protonated and dissolved, why proteins are stable in water, and why an amide behaves so differently from the amine it was made from.
The college version
Core Concepts
Classifying amines by substitution
An amine replaces one, two, or three hydrogens of ammonia (NH3) with carbon groups. A primary (1°) amine has one carbon group (R-NH2), a secondary (2°) amine has two (R2NH), and a tertiary (3°) amine has three (R3N); a quaternary ammonium ion A nitrogen with four carbon groups and a positive charge, R4N+. Full entry → has four, carrying a positive charge. The classification counts carbon groups on nitrogen, not on the carbon chain, and it predicts both the naming pattern and how many protons the amine can accept.
Naming amines and amides
Simple amines name the alkyl groups followed by -amine (ethylamine, dimethylamine), or use the prefix amino- when nitrogen is a substituent on a larger molecule. Amides name the parent acid and change the ending: ethanoic acid reacts with ammonia to give ethanamide, and the groups on nitrogen appear as N-substituents (N-methyl-ethanamide). The amide ending -amide always signals a carbonyl carbon attached to nitrogen.
Why amines are basic and amides are not
The nitrogen lone pair makes amines weak bases that accept protons: CH3NH2 + H+ → CH3NH3+. In an amide, that same lone pair is delocalized into the adjacent carbonyl group, so the nitrogen is far less willing to accept a proton. This single electronic difference explains why amines form salts with acids while amides mostly do not, and why the two families have different boiling points, smells, and biological roles.
Formation and hydrolysis of amides
Amides form when a carboxylic acid reacts with an amine (or ammonia), eliminating water in a condensation reaction Joining two molecules while eliminating a small molecule such as water. Full entry →. The reverse reaction, amide hydrolysis, uses water plus acid or base to split the amide back into a carboxylic acid and an amine. This forward–reverse pair is the chemistry of peptide bonds: amino acids join by amide (peptide) links, and digestion hydrolyzes those links. Nylon is a synthetic polyamide built from repeating amide bonds, and proteins are natural polyamides.
Common Confusions
| Do Not Confuse | With | Difference |
|---|---|---|
| Amine | Amide | Amine: no carbonyl, basic. Amide: carbonyl bonded to N, essentially nonbasic. |
| Primary amine | Primary alcohol | "Primary" counts carbon groups on nitrogen in an amine but on the -OH carbon in an alcohol. |
| Amide bond | Ester bond | Both are condensation links, but amides join acid + amine (N), esters join acid + alcohol (O). |
| Ammonia | Ammonium ion | Ammonia NH3 is a neutral weak base; ammonium NH4+ is its protonated, positively charged form. |
| Peptide bond | Hydrogen bond in proteins | Peptide bonds covalently link amino acids; hydrogen bonds fold and stabilize the chain. |
Eli explains
The same idea, in plain words
Explain it like I’m 10
Amines and amides are two families built around nitrogen. An amine is like ammonia that traded some of its hydrogens for carbon arms, and it still wants to grab extra hydrogen ions, which makes it a weak base. An amide has its nitrogen sitting next to a double-bonded oxygen, which "locks up" the nitrogen's spare electron pair, so it no longer acts like a base. That one difference explains why fish smell like amines but proteins (built from amide links) do not.
Worked examples
Consider three molecules: CH3CH2NH2, (CH3)2NH, and (CH3)3N. Count the carbon groups directly on nitrogen: ethylamine has one (1°), dimethylamine has two (2°), and trimethylamine has three (3°). Now add hydrochloric acid: each amine accepts a proton to form an ammonium salt, for example CH3CH2NH2 + HCl → CH3CH2NH3+Cl-. The salt is ionic and dissolves readily in water, which is exactly why pharmaceutical chemists convert poorly soluble amine drugs into hydrochloride salts for liquid formulations.
Write the condensation between ethanoic acid and methylamine. The acid's -OH and the amine's one -H leave as water, joining the carbonyl carbon to nitrogen:
CH3COOH + CH3NH2 → CH3CONHCH3 + H2O
The product, N-methyl-ethanamide, is an amide: its nitrogen lone pair is delocalized into the carbonyl, so unlike methylamine it will not accept a proton from dilute acid. Run the reaction backward with water and an acid or base catalyst and the amide hydrolyzes back to ethanoic acid and methylamine. Amino acids undergo the same condensation end to end, forming the peptide bonds of proteins, and the body hydrolyzes those bonds during digestion.
Key takeaways
- Amines are ammonia derivatives: 1° R-NH2, 2° R2NH, 3° R3N, plus charged quaternary ammonium ions.
- Amines are weak bases and react with acids to form water-soluble ammonium salts.
- Amides contain a carbonyl bonded to nitrogen and are essentially nonbasic because the nitrogen lone pair is delocalized.
- Amides form by condensation of a carboxylic acid with an amine (water eliminated) and hydrolyze back under acid or base catalysis.
- Peptide bonds in proteins and the links in nylon are amide bonds.
- Common amine names end in -amine; amides end in -amide, with N- prefixes for groups on nitrogen.
- Basic nitrogen drugs are often converted to salts to improve water solubility for injection.
Check yourself
5 review questions from the chapter. Try each one, then open the answer.
How is an amine classified as 1°, 2°, or 3°?
Show answer
Count the carbon groups bonded directly to nitrogen: one = primary, two = secondary, three = tertiary.
Why do amines react with acids, but amides generally do not?
Show answer
The amine's nitrogen lone pair accepts a proton; in an amide that lone pair is delocalized into the carbonyl group, so the nitrogen no longer acts as a base.
What small molecule is eliminated when an amide forms from a carboxylic acid and an amine?
Show answer
Water (H2O) is eliminated in the condensation.
How would you name the amide formed from ethanoic acid and ammonia?
Show answer
Ethanamide (from ethanoic acid, ending changed to -amide).
What structural unit repeats in nylon and in proteins?
Show answer
The amide bond (-CO-NH-), called a peptide bond in proteins.
Study tools & related lessonsKey vocabulary · Related
Key vocabulary
- amine
- An ammonia derivative with one or more carbon groups on nitrogen, R-NH2 to R3N.
- amide
- A compound with a carbonyl carbon bonded to nitrogen, R-CO-NH2.
- primary amine
- An amine with one carbon group on nitrogen, R-NH2.
- quaternary ammonium ion
- A nitrogen with four carbon groups and a positive charge, R4N+.
- lone pair
- A pair of valence electrons not involved in bonding.
- condensation reaction
- Joining two molecules while eliminating a small molecule such as water.
- peptide bond
- An amide link joining amino acids in proteins.
Sources & references
This lesson was adapted from the open educational references above; their licenses and attributions are preserved. See Copyright & Licensing.
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