Reactions of Amino Acids
- Amino acids are organic compounds that contain two functional groups:
- A basic amino (-NH2) group
- An acidic carboxylic acid (-COOH) group
- Due to the presence of both a basic and acidic group in amino acids, they are said to be amphoteric
- They can act as both acids and bases
Naturally occurring amino acids
- 2-aminocarboxylic acids are a type of amino acids in which the amine (-NH2) group is bonded to the carbon atom next to the -COOH group
- These type of amino acids form the ‘building blocks’ that make up proteins
- There are 20 naturally occurring amino acids with the general structural formula of RCH(NH2)COOH
General structural formula of amino acids
General structural formula of amino acids
- The R group varies in different amino acids and can be:
- Acidic
- Basic
- Neutral
The R group varies in different amino acids
Acid / base properties of amino acids
- Amino acids will undergo most reactions of amines and carboxylic acids including acid-base reactions of:
- Amines with acids
- Carboxylic acids with bases
Reactions of the amine group
- The amine group is basic and reacts with acids to make salts
- For example, a general amino acid reacts with hydrochloric acid to form the ammonium salt:
Reactions of the carboxylic acid group
Reaction with aqueous alkalis
- An amino acid reacts with aqueous alkali such as sodium or potassium hydroxide to form a salt and water
- For example, a general amino acid reacts with sodium hydroxide to form a sodium salt:
Esterification with alcohols
- Amino acids, like carboxylic acids, can be esterified by heating with alcohol in the presence of concentrated sulfuric acid
- The carboxylic acid group is esterified whilst the basic amine group is protonated due to the acidic conditions:
