Positive Test Production of a solid which subsequently dissolves and a reddish purple color develops, then compound contains oxygen. This constitutes a positive test. Complications Hydrocarbons, alkyl halides, diaryl ethers, and other high molecular weight ethers give a negative test. Most compounds in which the oxygen is in a carbonyl group in conjugation with an aromatic ring or a double bond produce a negative test. Such compounds include cinnamic acid, aromatic acids, aromatic esters, aromatic anhydrides, or aromatic ketones.
Phenols also give a negative test.
However, aromatic aldehydes give a positive test. Other compounds that produce a positive test are aliphatic acids, aliphatic aldehydes, aliphatic ketones, aliphatic esters, aliphatic anhydrides, and aliphatic ethers. This test should be used in conjunction with other tests. If the unknown produces a positive test, but yields a negative test for an aldehyde, a ketone, an ester, a carboxylic acid, or an anhydride, then the compound is an aliphatic or a low molecular weight ether.