# Does an acetal need to have one hydrogen attached to its carbon?

I was asked to identify the functional groups in this molecule above.

So far I have found an amide ($$\ce{-NHAc}$$), an ether ($$\ce{-OBn}$$), and a conjugated diene, but I was also told that there is an acetal ($$\ce{RHC(OR')2}$$).

However, in the only part of the molecule where I can see a carbon atom attached to two other oxygen atoms, the carbon atom is not attached to a hydrogen atom.

Where is the acetal group in this molecule?

According to the IUPAC definition, an acetal is any compound with a formula $$\ce{R2C(OR')2}$$ (R' ≠ H). In the past, "acetal" referred only to compounds of this type, which were derived from aldehydes (one R = H), however, it now broadly encompasses all compounds of this type, including those derived from ketones, which were formerly only referred to as ketals. Interestingly, there was a period of time in which use of the term "ketal" was discouraged (IUPAC says 'abandoned', but many chemists kept using it anyway), but it has now been re-embraced as a term, for the subset of acetals that are derived from ketones.