Abstract: The gas-phase conformations and isomerization reaction mechanism of cyclic 3′,5′-adenosine monophosphate(cAMP) were theoretically investigated using density functional theory at the B3LYP/6-31G** level.The resuts showed that cAMP has six conformations and the relevant bond lengths with relevant torsion angle for optimized geometries in the gas phase which is agreement with the experimental result.While the potential energy surfaces of reaction path showed that the rotation isomerization reaction...