A new description of equilateral five-membered rings during pseudorotation

An equilateral, five-membered ring is described based on the assumption that during conformational changes the distances between atoms and the position of the centre of mass of the ring remain constant. In the course of pseudorotation the atoms move along three-dimensional curves whose projections on a mean plane of the ring are circles. Assuming a certain bond length of the initial regular pentagon, the model allows for high accuracy calculations of the geometry of any future conformations of the ring. Our model is compared with those of Kilpatrick and Adams.