Question

how can esters be converted into soap?

Answer 1

The above process is known as Safonification .

Usually, a process by which triglycerides are reacted with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, called 'soap'.

so the compound added is NaOH with the complex esters to form soap

Answer 2

the process of making soap by alkaline hydrolysis of higher fatty acids and esters(oils) is called saponification reaction

when fats are treated with sodium hydroxide ,sodium salts and fatty acids , glycerol is formed.the sodium salts of these higher fatty acids being soaps the reaction is the soap formation reaction which is generally called as SAPONIFICATION reaction.