Noun
an organic compound usually formed as an intermediate product in the preparation of acetals from aldehydes or ketones
Source: WordNetDIBAH reduces esters to aldehydes. citation Direct reduction to give the corresponding ether is difficult as the intermediate hemiacetal tends to decompose to give an alcohol and an aldehyde (which is rapidly reduced to give a second alcohol). Source: Internet
The pK a for self-dissociation of ethanol is about 16 so the alkoxide ion is a strong enough base citation The addition of an alcohol to an aldehyde to form a hemiacetal is an example of a reaction that can be catalyzed by the presence of hydroxide. Source: Internet
Sucrose and trehalose are examples of non-reducing disaccharides because their glycosidic bond is between their respective hemiacetal carbon atoms. Source: Internet
Under acidic conditions, the hemiacetal and the alcohol can further react to form an acetal and water. Source: Internet
The resulting molecule has an hemiacetal or hemiketal group, depending on whether the linear form was an aldose or a ketose. Source: Internet