Formally, amidines are a class of oxoacids. The oxoacid from which an amidine is derived must be of the form RE(=O)OH, where R is a substituent. The −OH group is replaced by an −NH group and the =O group is replaced by =NR, giving amidines the general structure RE(=NR)NR. When the parent oxoacid is a carboxylic acid, the resulting amidine is a carboxamidine or carboximidamide (IUPAC name). Carboxamidines are frequently referred to simply as amidines, as they are the most commonly encountered type of amidine in organic chemistry.