In organic chemistry, alpha hydrogen refers to the hydrogen atoms that are attached to the carbon atom adjacent to a functional group, particularly in the context of carbonyl compounds such as aldehydes and ketones.
Specifically, in a carbonyl functional group (C=O), the carbon that is directly bonded to the carbonyl group is known as the alpha carbon. The hydrogen atoms bonded to this alpha carbon are termed alpha hydrogens. For instance, in acetone (a simple ketone), the two hydrogen atoms attached to the central carbon atom (the one flanked by the carbonyl) are alpha hydrogens.
Alpha hydrogens play a crucial role in various chemical reactions, such as enolate formation in the presence of a base. This reaction illustrates how alpha hydrogens can participate in important mechanisms, thus influencing the reactivity and properties of the organic molecules. Additionally, the acidity of alpha hydrogens is significant as they can be deprotonated to form a carbanion, which is essential in synthesis and various organic transformations.