The notation d, l, and dl (for dextrorotatory and laevorotatory, respectively) is used to designate the sign of optical activity . According to Basic terminology of stereochemistry (IUPAC Recommendations 1996) , this notation is obsolete and its usage is strongly discouraged. The recommended notation uses the prefixes (+), (−), and (±), respectively. Since optical rotation is a distinguishing characteristic of enantiomers, the notation using d, l, and dl as well as the notation using (+), (−), and (±) can be used to distinguish the enantiomers of a chiral molecule. However, without further information, the absolute configuration ( R or S ) of the chiral molecule is indeterminable. Thus, it remains unknown whether the dextrorotatory enantiomer ( d and (+), respectively) is the R enantiomer or the S enantiomer. The notation D, L, and DL is based on the arbitrary convention according to whi