Ring strain

Angle strain: how far each C–C–C angle is from 109.47°. Torsional strain: in a planar ring every C–C bond is eclipsed (H–C–C–H dihedral 0°). The experimental strain energies (heats of combustion per CH₂, relative to a strain-free chain) are the textbook values.

Press Optimize to watch the ring relax. Where a quantum-chemical result is available (ORCA, r2SCAN-3c, started from this exact ideal geometry) the model moves to it; otherwise a simple force field inside the page does a labelled clean-up. Either way the badge turns amber and says what moved, and Back to ideal restores the textbook geometry.

The diamond lattice has no rings smaller than six, so cyclopropane, cyclobutane and cyclopentane cannot be built on it. They are drawn planar with ideal bond lengths and ideal H–C–H angles; the ring angles are whatever a regular polygon forces (60°, 90°, 108°), and the badge lists exactly those, plus the eclipsed C–C bonds. Real cyclobutane and cyclopentane pucker to trade a little angle strain for less eclipsing; the planar forms show each strain at its purest.