Adsorption and desorption of trans-2-methyl-2-pentenoic acid in dichloromethane has been investigated by using in situ attenuated total reflection infrared spectroscopy. Asymmetric hydrogenation of trans-2-methyl-2-pentenoic acid in hexane over two well defined E-40692 and E-5220 Engelhard Pd/Al2O3 catalysts modified with cinchonidine has been studied.