Abstract

<h2>Acta Crystallographica Section B</h2><h3>Structural Science</h3><h3>0108-7681</h3> <h2>research papers</h2> Volume 40 Part 5 Pages 498-500 October 1984 <h2>On the correct usage of the Cremer-Pople puckering parameters as quantitative descriptors of ring shapes - a reply to recent criticism by Petit, Dillen and Geise</h2> D. Cremer Acta Cryst. (1984). B40, 498-500 On the Correct Usage of the Cremer-Pople Puckering Parameters as Quantitative Descriptors of Ring Shapes - a Reply to Recent Criticism by Petit, Dillen and Geise BY DIETER CREMER Lehrstuhl fiir Theoretische Chemie, Universiffit K6In, K6In, D-5000, Federal Republic of Germany (Received 11 January 1984; accepted 25 April 1984) Abstract The Cremer-Pople puckering parameters define the conformation of a puckered ring in a quantitative, mathematically well defined manner. Recent results by Petit, Dillen & Geise [Acta Cryst. (1983), B39, 648-651] on six-membered-ring conformations are due to an erroneous definition of standard boat and twist-boat forms. This is shown by deriving the correct relationships between puckering parameters and internal ring angles for these forms. The analysis of the puckered forms of an N- membered ring is uniquely carried out by calculating the mean plane (MP) and the puckering parameters of the ring (Cremer & Pople, 1975a; Cremer, 1980). This approach is