Aqueous conditions reduction hydrogenolysis, hydrogenation

For aliphatic aldehydes and ketones, reduction to the alcohol can be carried out under mild conditions over platinum or the more-active forms of Raney nickel. Ruthenium is also an excellent catalyst for reduction of aliphatic aldehydes and can be used to advantage with aqueous solutions. Palladium is not very active for hydrogenation of aliphatic carbonyl compounds, but is effective for the reduction of aromatic aldehydes and ketones excellent yields of the alcohols can be obtained if the reaction is interrupted after absorption of one mole of hydrogen. Prolonged reaction, particularly at elevated temperatures or in the presence of acid, leads to hydrogenolysis and can therefore be used as a method for the reduction of aromatic ketones to methylene compounds. 

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