Processes for the preparation and purification of hydrofluoroolefins such as tetrafluorinated propenes. A process is provided for separating a first hydrofluoroolefin from a second hydrofluoroolefin by a) providing a mixture comprising a first hydrofluoroolefin and a second hydrofluoroolefin, which first hydrofluoroolefin is preferentially more reactive with an amine than the second hydrofluoroolefin; b) adding a sufficient amount of an amine to the mixture to form a combination comprising the second hydrofluoroolefin and a reaction product of the first hydrofluoroolefin and the amine; and then c) separating the reaction product from the combination. This is particularly useful for removing 1,2,3,3,3-pentafluoropropene (HFO-1225ye) impurities from the hydrofluoroolefin 2,3,3,3-tetrafluoropropene (HFO-1234yf). HFO-1234yf is a refrigerant with low global warming potential.