Hydrolysis of benzaldehyde diethyl acetal, 2-phenyl-1,3-dioxolane and 2-phenyl-1,3-oxathiolane occurs at relatively similar rates in the presence of acidic zeolites compared to the large difference observed in solution. A similar behavior is again observed with the corresponding acetals and thioacetals of furfural. In a similar way, hydrogenolysis of benzaldehyde diethyl acetal, 2-phenyl-1,3-dioxolane and 2-phenyl-1,3-oxathiolane also occurs at relatively similar rates in the presence of sulfided catalysts. The weak difference in the observed reaction rates could be interpreted in terms of stereoelectronic effects, i.e. through a most favorable adsorption of cyclic acetals and thioacetals as due to the orientation of their oxygen or sulfur electron lone pairs, thus leading to a better electron transfer to protonic species in the case of zeolites and to anionic vacancies in the case of sulfided catalysts.