# 17.11: Tricarbonyl Compounds


The properties of tricarbonyl compounds are for the most part as expected, except when the three groups are contiguous to one another, as in diphenylpropanetrione. With such compounds, the central carbonyl group is highly reactive; it is lost, as carbon monoxide, in the presence of acidic catalysts such as aluminum chloride, and adds water readily to give a monohydrate:

We shall consider the hydrate of the cyclic triketone, $$18$$, known as "ninhydrin", later in connection with amino acids: