Figure 2. The figure shows the projection of the heavy-atom skeleton onto the X-H···Y plane for cases where H-bonding can result in a: (a) Five-member ring; (b) Six-member ring; or (c) Seven-member ring

From

It Is Important to Compute Intramolecular Hydrogen Bonding in Drug Design?

María J. R. Yunta

American Journal of Modeling and Optimization. 2017, 5(1), 24-57 doi:10.12691/ajmo-5-1-3