Question

use of P4H10 as reagent​

Answer 1

Answer:

In general, any alkyl or aryl amide reacts with P4O10 to give the corresponding cyanide, or nitrile. Here, benzamide would give benzonitrile. I am not really sure about the mechanism, but P4O10 is a dehydrating agent, and if you look at the formulae of reactant and product, you'd notice that H2O is lost.