An acetal is a functional group or molecule containing the functional group of a carbon bonded to two -OR groups.

where R, R' and R&apos&apos are all carbon backbones.

Acetals can be used as carbonyl-protecting groups.

Reactions

Synthesis

1. Nucleophilic addition of an alcohol to a resonance stabilized cation
   • hemiacetal + alcohol + acid (catalyst) ↔ acetal + water

An acetal can, under certain conditions, be converted back into a hemiacetal and an alcohol.