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5.5.1Unit 5. Transition Metals and Organic Nitrogen Chemistry

Amines, Amides and Amino Acids – Introduction — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 5 parts Lesson 31 of 43 Unit quiz

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Curriculum Equation Key pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: pH + pOH = 14
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Part 1 of 5Amines

5.5.1 Amines, Amides and Amino Acids - Introduction
Primary
  • One alkyl or aryl group attached to nitrogen, RNH₂, as in ethylamine.
Secondary
  • Two groups attached to nitrogen, R₂NH, as in dimethylamine.
Tertiary
  • Three groups attached to nitrogen, R₃N, as in trimethylamine.
Quaternary ammonium
  • Four groups attached to nitrogen, R₄N⁺, which has no lone pair.
Naming
  • Primary amines are named with the suffix -amine, for example propylamine or propan-1-amine, and substituents on nitrogen use the prefix N-.

Part 2 of 5Amides and Amino Acids

Amides and Amino Acids
Amide
  • Contains the group -CONH₂, named by changing the acid ending to -amide, as in ethanamide.
Amino acid
  • Contains both -NH₂ and -COOH, with general formula H₂NCHRCOOH.
Naming
  • 2-aminopropanoic acid has the amino group on the carbon next to the acid group.
Amino acid in solid
  • Exists as a zwitterion, ⁺H₃NCHRCOO⁻, with both a positive and a negative charge in the same molecule.

Part 3 of 5Properties

Properties
Lone pair
  • The nitrogen of an amine has a lone pair that can accept H⁺ or attack electron-poor carbon atoms.
Hydrogen bonding
  • Primary and secondary amines form hydrogen bonds with each other and with water.
Boiling points
  • These are higher than alkanes of similar mass but lower than alcohols, because N-H···N bonds are weaker than O-H···O.
Amino acids
  • They have high melting points and dissolve well in water because of ionic attractions in the zwitterion.
Solubility
  • Small amines dissolve readily in water, but solubility falls as the hydrocarbon chain gets longer and the non-polar part dominates.
Compound typeFunctional groupBasic?
Amine-NH₂Yes
Amide-CONH₂No, neutral
Amino acid-NH₂ and -COOHAmphoteric

Part 4 of 5Worked Example

Question Classify (CH₃)₂NH and name the compound.

  1. Two methyl groups are bonded to nitrogen, so it is a secondary amine.
  2. The name is dimethylamine.

Answer Secondary amine; dimethylamine

Part 5 of 5Exam Checklist & Tips

5.5.1 – Key Points for the Exam

  • Amine A compound derived from ammonia with alkyl or aryl groups.
  • Amide A compound with the -CONH₂ group.
  • Zwitterion A molecule with both positive and negative charges.
  • Amphoteric Able to react as an acid or a base.

Common Mistakes

  • Mixing up primary and secondary by counting carbons rather than groups on nitrogen.
  • Saying amides are basic.
  • Writing the amino acid as neutral in the solid state.
  • Placing the amino group on the wrong carbon when naming.

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