The decomposition behavior of titanium tetraisopropoxide [TTIP, Ti(OC3H7)(4)] on Si(100) has been studied using a thermal desorption technique in vacuum. TTIP is dissociated on Si(100) at temperatures below 350 K so that the silicon surface is covered with isopropoxy ligands and hydrogen, which originate from the TTIP. The isopropoxy ligands react with hydrogen on the silicon surface to produce isopropanol at temperatures between 350 and 650 K, and some of the ligands produce propylene and acetone in the range of 500-700 K. Hydrogen exists as monohydride on the silicon surface showing a characteristic desorption peak at 780 K. At higher dosages, TTIP is not completely dissociated and some of the isopropoxy ligands remain bound to titanium even at 700 K. These intact ligands of TTIP produce acetone/isopropanol or propylene in the temperature range of 800-1000 K by disproportionation among themselves or by the simple decomposition of the C-O bond in the ligands.