In organic chemistry, an aminal or aminoacetal is a functional group or type of organic compound that has two amine groups attached to the same carbon atom: \sC(NR2)(NR2)\s. (As is customary in organic chemistry, R can represent hydrogen or an alkyl group). A common aminal is bis(dimethylamino)methane, a colorless liquid that is prepared by the reaction of dimethylamine and formaldehyde: Aminals are encountered in, for instance, the Fischer indole synthesis. Several examples exist in nature. Hexahydro-1,3,5-triazine ((CH2NH)3), an intermediate in the condensation of formaldehyde and ammonia, tends to degrade to hexamethylene tetraamine. Cyclic aminals can be obtained by the condensation of a diamine and an aldehyde. Imidazolidines are one class of these cyclic aminals.