What small molecules are usually lost during condensation polymerisation?

During condensation polymerisation, small molecules are released as by-products when monomers join to form polymers. Water is the most common small molecule that is lost in this process. This type of reaction typically involves the formation of covalent bonds between different monomers, and during this bonding, hydroxyl (-OH) groups from one monomer join with hydrogen atoms from another, resulting in the elimination of water.

In contrast, carbon dioxide, ammonia, and oxygen are not typically by-products of condensation polymerisation. Carbon dioxide is usually associated with different types of chemical reactions, such as combustion or fermentation. Ammonia can be involved in other types of reactions, particularly those related to nitrogenous compounds, but is not a product of condensation polymerisation. Similarly, oxygen does not usually feature as a product in this context. Therefore, water is the small molecule that is characteristically lost during condensation polymerisation.