Propylparaben also called as Propyl 4-hydroxybenzoate (PHB), is a p-hydroxybenzoate derivative. It can be prepared by reacting p-hydroxybenzoic acid with n-propanol in the presence of an acidic ionic liquid.It crystallizes in the monoclinic space group P21/c.Propyl 4-hydroxybenzoate belongs to a group called parabens.