Undesirable by-products form due to various reasons, such as:
1. Side Reactions: Reactions other than the main catalytic pathway can occur. 2. Catalyst Deactivation: Degraded or poisoned catalysts often lead to incomplete reactions. 3. Reaction Conditions: Temperature, pressure, and concentrations can influence the selectivity of the catalyst. 4. Impurities: Presence of contaminants in the reactants can lead to unwanted reactions.
