Amino acidsAQA A-Level Chemistry: Mind map

Exam questions on Amino acids

1. Glycine, H₂N–CH₂–COOH, is the simplest amino acid. In the solid state and in neutral aqueous solution it exists mainly as a zwitterion.
   Explain how glycine forms a zwitterion.2 marks
2. A student dissolves alanine, CH₃CH(NH₂)COOH, in solutions of different pH: dilute hydrochloric acid, water and aqueous sodium hydroxide.
   Write an equation for the reaction of alanine with aqueous sodium hydroxide, showing the structure of the organic product.2 marks
3. Glycine, H₂NCH₂COOH, is a white crystalline solid that melts above 200 °C. Propanoic acid, CH₃CH₂COOH, has almost the same relative molecular mass but is a liquid at room temperature.
   Explain why glycine, Mr = 75.0, is a solid at room temperature but propanoic acid, Mr = 74.0, is a liquid.3 marks