. An example is of an hemiaminal is that obtained from reaction of secondary amine carbazole and formaldehyde Those generated from primary amines are unstable to the extent that they've never been isolated and very rarely been observed directly. In a 2007 study a hemiaminal substructure trapped in the cavity of a host-guest complex was studied with a chemical half-life of 30 minutes. Because both amine and carbonyl group are isolated in a cavity, hemiaminal formation is favored due to a high f… (More on Hemiaminal)