Reactions that break apart large molecules are involved in which type of digestion?

They are involved in a chemical digestion. 
Chemical digestion involves breaking down the food into simpler nutrients that can be used by the cells. It begins in the mouth when food mixes with saliva which contains enzyme salivary amylase that breaks down carbohydrates. It also occurs in the stomach where HCl and pepsin forms chyme and small intestine especially in the duodenum.