Steric Effects on Nucleophilic Addition Reactions

In the product, they are approximately 109° apart. Therefore, there is more crowding in the product than in the reactant. Thus, increasing the size of the groups attached to the carbonyl carbon atom also decreases the equihbrium constant for hydration. 

The carbonyl group of an aldehyde (a) is less stericaUy hindered than the carbonyl group of a ketone (b). Therefore, ketones react more slowly than aldehydes in nucleophilic addition reactions. The nucleophile here is water. 

The hydrate of an aldehyde (a) is less StericaUy hindered than the hydrate of a ketone (b). 

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