Conformations of linear chains. Systematics and suggestions for nomenclature

There are six categories of calculated favored dihedral angles in linear Mn X2n+2 chains. The Prelog-Klyne nomenclature is not helpful for classifying them, and we propose the following labels and symbols: A, anti, reserved fo r torsional angles within a few degrees of 180 degrees; T, transoid, omega similar or equal to 165 degrees; D, deviant, omega similar or equal to 150 degrees; O, ortho, omega similar or equal to 90 degrees; G, gauche, omega s imilar or equal to 60 degrees; C, cisoid, omega similar or equal to 40 degr ees. With the exception of C, all of these categories have been observed in alkanes, perfluoroalkanes, or oligosilanes.