Pyrogallarene shows concentration-dependent instability in dilute solutions resulting in elimination of two ketene molecules and formation of pyrogallarene lactones. This unexpected phenomenon, which is not observed with resorcinarenes, highlights the significance of the four hydroxyl groups at 2-position for the molecular characteristics of pyrogallarenes.
Kalenius, E., Beyeh, N. K., Jänis, J., & Rissanen, K. (2011). The inherent structural instability: concentration-dependent transformation of pyrogallarene to pyrogallarene lactones. Chemical Communications, 47(9), 2649-2651. https://doi.org/10.1039/C0CC05280A