Exact method for the calculation of pseudorotation parameters P, τm and their errors. A comparison of the Altona–Sundaralingam and Cremer–Pople treatment of puckering of five-membered rings

摘要: A comparison of the two methods available for describing puckering five-membered rings - Altona-Sundaralingam (A-S) [Altona & Sundaralingam (1972). J. Am. Chem. Soc. 94, 8205-8212] pseudorotation parameters τm, P and Cremer-Pople (C-P) [Cremer Pople (1975). 97, 1354-1358] q, ϕ shows that they are same all practical purposes but both have minor shortcomings. In A-S method, value τm is somewhat dependent on choice origin atom, while in C-P method normal to mean plane, rather than being fixed, precesses as ring changes. We present here an exact procedure obtaining correspond amplitude phase Fourier wave period 4π/5, thus making independent atom. Formulae also given estimation standard deviations parameters.