Introduction: Use of Hammett equation dealing with meta and para-substituted benzene derivatives and Taft equation dealing with ortho-substituted benzene derivatives in elucidating the reaction mechanisms in organic chemistry is indubitable. Since their introduction numerous publications have appeared in literature and still being published to date. Application of Hammett equation and Taft equation to five membered aromatic heterocyclic ring systems was less commonly studied. The first application of Hammett law (not as an equation) to furan ring was with 5-X-2-furoic acids . But this was quoted in reference as it was published in 1935 even before the Hammett equation came into existence. In reference by Freeman it is surprising to see even a Hammett ρ value was reported for the dissociation of 5-X-2-furoic acids without knowing Hammett σ values because evaluation of Hammett σ values took place only in 1937 . In spite of numerous works on the application of Hammett and Taft equations in organic chemistry, their application to five membered ring systems did not find much place in chemistry research except a one-page small publication appeared 50 years ago and references cited there in. In this publication the information of substituents in furan and thiophene derivatives used did not find a place. In the present work we tried a deep insight with a total of 12 heterocyclic systems.