It has been shown in our previous work [1] that molecule of fungicide, vinclozolin, coordinated to the wet irradiated TiO2 surface can be decomposed by means of free hydrogen atoms. Moreover, free vinclozolin molecules within water film on the given surface can be decomposed by free protons. However, the present DFT results (B3LYP, 6-31G [2]), show that free protons do not break the hydantoin ring of iprodione due to formation of stable intramolecular hydrogen bonds. At the same time, free iprodione (IPR) molecules interact with free hydroxyl anions (which destroy their hydantoin cycles) and can be easily and irreversibly transformed (hydralized) into N-(3,5-dichloroanilinocarbonyl)-N-(isopropylaminocarbonyl) glycine (see Figure 1).Figure 1. Decay of the hydantoin ring of IPR by OHThe above theoretical conclusion is in a good agreement with the experimental data [3]. In their turn, the molecules of iprodione adsorbed on the surface of the nano-cluster [Ti24O50H4] can be decomposed by means of free protons giving the following end products: isopropylisocyanate and 3-(3,5-dichlorophenyl)-hydantoin. Figure 2 demonstrates the mechanism of this decay.Figure 2. Decay of protonated IPR molecule bounded to nanocluster [Ti24O50H4]