On 100K rutile TiO 2 (110) surfaces with 3.5±0.5% surface bridge-bonded oxygen vacancies (BBO V ’s), propene formation by dehydration of 2-propanol was monitored by temperature programmed desorption (TPD). The BBO V ’s were either filled or unfilled when the 2-propanol was dosed. Propene desorption rates exhibit two local maxima, nominally at 350 (LT) and 570K (HT). The former is not altered by filling BBO V ’s while the latter is reduced by factors of 2.5 and 5 when the vacancies are pre-filled with water (H–OH) and alcohol (R–OH), respectively. The HT process is attributed to a reaction of 2-propoxy groups located on surface BBO’s. To account for much of the HT C 3 H 6 yield when BBO V ’s are filled before (CH 3 ) 2 CHOH dosing, we propose a model whereby, during TPD, vacancies form and are filled with 2-propoxy. The factor of two difference between titrating BBO V ’s with H 2 O and alcohols is attributed to stoichiometry; twice as many OH groups form on surface BBO rows when H 2 O is used so twice as many vacancies are created when OH recombines.