The reaction of N-phenyltriazolinedione with three simple alkyl-substituted alkenes in water/alcohol or water/acetone solution was found to give a mixture of the corresponding ene and water addition products. The new hydration products were characterized by spectroscopy, and in one case, also by X-ray diffraction analysis. Thermodynamic parameters were determined for the reactions involving 2-methylbut-2-ene, TriME, and 2, ...