Triethyl orthoacetate is the ethyl orthoester of acetic acid. It is also known as 1,1,1-triethoxyethane, and is an oily liquid with a colour that is anywhere from yellow to colorless. It is also known for its pungent odour. Triethyl orthoacetate is used in organic synthesis for the introduction of the acetate group to an alcohol. It is also used in the Johnson-Claisen rearrangement.