How nitrogen compounds and biomolecules build living matter
Amines are derivatives of ammonia in which hydrogen atoms are replaced by alkyl or aryl groups, giving primary, secondary and tertiary amines. The lone pair on nitrogen makes them basic. In water, aliphatic amines are more basic than ammonia, while aniline is weaker because its lone pair is delocalised into the benzene ring. The Hinsberg test separates the three types, and the carbylamine test identifies primary amines by a foul smell. Aniline reacts with nitrous acid at 0–5 °C to form benzenediazonium chloride, used to make dyes.
Biomolecules are the organic compounds of life. Carbohydrates include monosaccharides like glucose, disaccharides like sucrose and polysaccharides like starch and cellulose. Proteins are polymers of α-amino acids joined by peptide bonds, with primary, secondary, tertiary and quaternary structure; denaturation destroys their shape. Nucleic acids, DNA and RNA, are made of nucleotides containing a sugar, a phosphate and a nitrogenous base. Vitamins and enzymes are also biomolecules.
Why it matters
Azo dyes made from diazonium salts colour fabrics and food, and many medicines, such as paracetamol and antihistamines, contain amine groups. Understanding carbohydrates and proteins explains nutrition and digestion, enzymes speed up reactions in the body, and DNA carries genetic information. This chemistry is the basis of biochemistry, medicine and biotechnology.
Key terms
- Amine
- An organic compound derived from ammonia by replacing hydrogen atoms with carbon groups.
- Diazonium salt
- A compound containing the –N₂⁺ group, formed from aromatic amines and nitrous acid at low temperature.
- Peptide bond
- The amide link formed between the carboxyl group of one amino acid and the amino group of another.
- Nucleotide
- The building unit of nucleic acids, made of a sugar, a phosphate group and a nitrogenous base.