The simplest large-scale procedure for reduction of aldehydes and ketones to alcohols is by catalytic hydrogenation. Catalytic hydrogenation is simultaneously an addition reaction (addition of H2) and a reduction (gain of hydrogen). The product is an alcohol. Aldehydes produce primary alcohols, while ketones produce secondary alcohols. Tertiary alchols cannot be obtained from aldehydes and ketones. This reaction is the opposite of oxidation.
The advantage over most other kinds of reduction is that usually the product can be obtained simply by filtration from the catalyst, then distillation. The common catalysts are nickel, palladium, or platinum. Hydrogenation of aldehyde and ketone carbonyl groups is much slower than of carbon-carbon double bonds so more strenuous conditions are required. This is not surprising, because hydrogenation of carbonyl groups is calculated to be less exothermic than that of carbon-carbon double bonds:
Contributors and Attributions
John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."