Bosentan Monohydrate(1), is the first of a new drug class, anEndothelinreceptor antagonist and belongs to of highly substituted pyrimidine derivatives with no chiral centres used for treatment of pulmonary arterial hypertension(PAH).One of the known impurity in Bosentan Monohydrate is,N,N’-(ethane-1,2diyl{oxy[5-(2- methoxy)-2,2’-bipyrimidine-6,4-diyl]})bis(4-tert-butylbenzenesulphonamide(Dimer)(2), is formed during the laboratory optimization and later during its bulk synthesis. This impurity is synthesized by novel method and characterised it by 1H-NMR, I.R., & Mass Spectroscopy.