The compound formed by acid shrinkage, such as a carbonic acid molecule (H2CO3) shrinking a molecule of water (H2O) and the remaining carbon dioxide (CO2) is carbonic anhydride. Two vinegar molecules (CH3COOH) shrink one molecule of water (H2O) and the remaining ((CH3CO)2O) is acetic anhydride.
Acetic anhydride is not an oxide.