Now, we can say here that aldehydes and ketones are reduced to primary and secondary alcohols respectively. The reducing agent within these processes is H2. And the catalyst that helps facilitate this reduction, we can have them as metals which are Ni (nickel), platinum, or palladium. Now the whole process, the whole result of this reduction is that the carbonyl oxygen gains an h and the carbonyl carbon also gains an h. If we take a look here, we start out with an aldehyde. We're reducing it with H2 and nickel. Remember reduction means we have to try to make as many carbon-hydrogen bonds as we can without breaking any carbon-carbon bonds. To do this, we'd have to break one of the carbon-oxygen bonds here. And when we break that bond, carbon still needs to make its 4 bonds and oxygen would ideally want to still make its 2. So, this H2 basically gives itself up: one h goes to the carbon, the other h goes to the oxygen. As a result of this, we see that we made a primary alcohol.
A ketone, well, a ketone follows the same process. We're going to say we use H2. And remember, we could use nickel, platinum, or palladium as our metal catalyst. And again, we're trying to get rid of one of these carbon-oxygen bonds. To make up for that loss, carbon's going to bond to a hydrogen and oxygen is going to bind to a hydrogen. What we make now is a secondary alcohol. So just remember, when it comes to reduction, both aldehydes and ketones can be reduced. Aldehydes typically create primary alcohols. Ketones primarily make secondary alcohols. Okay. So, they're going to make secondary alcohols once they undergo reduction. Alright. So just keep that in mind.