In the following reaction, product P is

The reactant given in the reaction is acid chloride, and it is reacted with hydrogen in the presence of palladium supported over barium sulfate, so the formation of aldehyde will take place and hydrochloric acid is also produced. This reaction is known as Rosenmund reduction. So, the reaction is given below: 푅−퐶푂−퐶푙 퐻2+푃푑−퐵푎푆푂4 → 푅−퐶퐻푂