Overview
This lecture covers the structures, properties, and biological roles of amines and amides, including their chemical behavior, functional group identification, and significance in biological molecules and synthetic materials.
Structure and Properties of Amines
- Amines contain a nitrogen atom with a lone pair and three bonds to hydrogen and/or carbon.
- Naming amines uses the suffix “-ine” (e.g., methylamine, dimethylamine).
- Amines can be part of aromatic heterocycles, such as pyridine, where nitrogen replaces a carbon in the ring.
- The nitrogen's lone pair makes amines weak bases, similar to ammonia.
- Amines are widespread in biomolecules (amino acids, neurotransmitters, DNA) and pharmaceuticals (penicillin, codeine).
Amines in Life and Society
- DNA is composed of nucleotides, each with a nitrogenous base, a sugar, and a phosphate group.
- DNA uses hydrogen bonding between nitrogenous bases to form a double helix.
- DNA fingerprinting is possible due to genetic sequence similarities and differences.
Alkaloids and Biological Activity
- Alkaloids are plant-derived cyclic amines with strong physiological effects (e.g., nicotine, morphine, heroin).
- Alkaloids are basic and react with acids to form salts, aiding in their extraction.
- Small structural changes in alkaloids can significantly alter their effects (e.g., morphine vs. codeine vs. heroin).
Structure and Properties of Amides
- Amides feature nitrogen bonded to the carbonyl carbon of a carboxylic acid derivative.
- Naming amides uses the suffix “-amide” (e.g., acetamide, hexanamide).
- Amides form via a condensation (amidation) reaction between carboxylic acids and amines or ammonia, releasing water.
Biological Importance of Amides: Proteins and Enzymes
- Amino acids have both an amine group (NH₂) and a carboxylic acid group (COOH).
- Proteins form when amino acids link via peptide (amide) bonds, creating polypeptide chains.
- Enzymes are specific protein catalysts that accelerate reactions by lowering activation energy.
Applications: Kevlar and Synthetic Polyamides
- Kevlar is a strong synthetic polyamide formed from 1,4-phenylene-diamine and terephthaloyl chloride.
- Kevlar's strength comes from hydrogen bonding between polymer chains and aromatic stacking.
- Kevlar is used in body armor, tires, fire-resistant clothing, and marine applications.
Key Terms & Definitions
- Amine — An organic molecule with a nitrogen atom bound to carbon and/or hydrogen; weak base.
- Amide — Compound with nitrogen attached to the carbonyl carbon; product of amine and carboxylic acid reaction.
- Alkaloid — Naturally occurring amine in plants, often with potent biological effects.
- Polypeptide — Chain of amino acids linked by peptide (amide) bonds.
- Peptide Bond — Covalent bond between the carboxyl group of one amino acid and the amine group of another.
Action Items / Next Steps
- Review functional group structures for amines and amides.
- Study the mechanisms of amidation and peptide bond formation.
- Prepare for questions on the biological and synthetic importance of amines and amides.