Amino Acids: Zwitterions
The isoelectric point of an amino acid is the pH at which there is no net electrical charge.
At a pH which is more acidic than the isoelectric point, the amino acid behaves as a base and accepts a proton from the acid, becoming postively charged.
At a pH which is more alkaline than the isoelectric point, the amino acid behaves as an acid and donates a proton to the base, becoming negatively charged.
Hydrolysis of polypeptides
Acid hydrolysis: A water molecule and 2 protons/an aqueous acid are needed to break a dipeptide into the amino acids that made it. The amino acids formed are positively charged due to the presence of protons in the acid. The polypeptide is heated under reflux with 6 mol per decimetre cubed of HCl for 24 hours.
Alkaline hydrolysis: Aqueous sodium hydroxide is used at just above 100c.
Hydrolysis of Polyesters
Hydrolysis of Polyamides
Synthesis of Aliphatic Compounds
Synthesis of Aromatic Compounds